#include "fgc/Config.h"
#include "fgc/FirmwareConfig.h"
#include "fgc/Logger.h"
#include "fgc/Paths.h"

#include <cmath>
#include <algorithm>
#include <cctype>
#include <cstdio>
#include <cstdlib>
#include <filesystem>
#include <fstream>
#include <sstream>
#include <stdexcept>

extern "C" {
#include "ini.h"
}

namespace fgc {

namespace fs = std::filesystem;

namespace {

std::string get(const std::map<std::string, std::string>& kv, const std::string& key,
                const std::string& fallback = "") {
    auto it = kv.find(key);
    return (it != kv.end() && !it->second.empty()) ? it->second : fallback;
}

int getInt(const std::map<std::string, std::string>& kv, const std::string& key, int fallback) {
    auto it = kv.find(key);
    if (it == kv.end() || it->second.empty()) return fallback;
    try {
        // Reject trailing characters: bare std::stoi stops at the first non-digit,
        // so "1883x" would quietly become 1883 and a typo'd value would configure
        // something the operator never wrote. Same reasoning as getIntAutoBase below.
        size_t consumed = 0;
        int out = std::stoi(it->second, &consumed);
        if (consumed != it->second.size()) throw std::invalid_argument("trailing characters");
        return out;
    } catch (const std::exception&) {
        throw std::runtime_error("Config key '" + key + "' must be an integer, got '" +
                                 it->second + "'");
    }
}

// Like getInt, but accepts an "0x"-prefixed value too. Only for I2C addresses,
// which every datasheet, `i2cdetect` and our own docs write in hex: plain
// std::stoi() stops at the 'x' and silently yields 0, so `i2c_addr = 0x44`
// would configure address 0x00 and the sensor would never answer. Kept separate
// from getInt so no other key gains surprise octal ("010" -> 8) parsing.
int getIntAutoBase(const std::map<std::string, std::string>& kv, const std::string& key,
                   int fallback) {
    auto it = kv.find(key);
    if (it == kv.end() || it->second.empty()) return fallback;
    try {
        size_t consumed = 0;
        const std::string& v = it->second;
        int out = std::stoi(v, &consumed, v.rfind("0x", 0) == 0 || v.rfind("0X", 0) == 0 ? 16 : 10);
        if (consumed != v.size()) throw std::invalid_argument("trailing characters");
        return out;
    } catch (const std::exception&) {
        throw std::runtime_error("Config key '" + key + "' must be an integer (decimal or 0x hex)"
                                 ", got '" + it->second + "'");
    }
}

double getDouble(const std::map<std::string, std::string>& kv, const std::string& key,
                 double fallback) {
    auto it = kv.find(key);
    if (it == kv.end() || it->second.empty()) return fallback;
    try {
        return std::stod(it->second);
    } catch (const std::exception&) {
        throw std::runtime_error("Config key '" + key + "' must be a number, got '" +
                                 it->second + "'");
    }
}

long getLong(const std::map<std::string, std::string>& kv, const std::string& key, long fallback) {
    auto it = kv.find(key);
    if (it == kv.end() || it->second.empty()) return fallback;
    try {
        return std::stol(it->second);
    } catch (const std::exception&) {
        throw std::runtime_error("Config key '" + key + "' must be an integer, got '" +
                                 it->second + "'");
    }
}

bool getBool(const std::map<std::string, std::string>& kv, const std::string& key, bool fallback) {
    auto it = kv.find(key);
    if (it == kv.end() || it->second.empty()) return fallback;
    const std::string& v = it->second;
    if (v == "1" || v == "true" || v == "yes" || v == "on") return true;
    if (v == "0" || v == "false" || v == "no" || v == "off") return false;
    throw std::runtime_error("Config key '" + key + "' must be a boolean, got '" + v + "'");
}

// "yaw, pitch" -> {"yaw","pitch"}. Lowercased and trimmed; empty entries dropped,
// so trailing commas and stray spacing are not errors an operator has to hunt.
std::vector<std::string> splitList(const std::string& s) {
    std::vector<std::string> out;
    std::string              cur;
    auto flush = [&] {
        size_t a = cur.find_first_not_of(" \t");
        if (a == std::string::npos) { cur.clear(); return; }
        size_t b = cur.find_last_not_of(" \t");
        std::string t = cur.substr(a, b - a + 1);
        for (char& c : t) c = static_cast<char>(std::tolower((unsigned char)c));
        if (!t.empty()) out.push_back(t);
        cur.clear();
    };
    for (char c : s) {
        if (c == ',') flush();
        else cur += c;
    }
    flush();
    return out;
}

std::string lowered(std::string s) {
    for (char& c : s) c = static_cast<char>(std::tolower((unsigned char)c));
    return s;
}

std::string envOr(const char* name, const std::string& fallback) {
    const char* v = std::getenv(name);
    return (v && *v) ? std::string(v) : fallback;
}

// inih callback: flatten "Section.name" => value into the map.
int iniHandler(void* user, const char* section, const char* name, const char* value) {
    auto* kv = static_cast<std::map<std::string, std::string>*>(user);
    (*kv)[std::string(section) + "." + std::string(name)] = value ? value : "";
    return 1;
}

}  // namespace

CameraProfileTiming CameraSpec::timingFor(const std::string& profile_name) const {
    auto it = timing.find(profile_name);
    return it != timing.end() ? it->second : CameraProfileTiming{};
}

std::vector<const CameraSpec*> CameraConfig::active() const {
    std::vector<const CameraSpec*> out;
    for (const auto& c : cameras)
        if (c.enabled) out.push_back(&c);
    return out;
}

int CameraConfig::maxSettleWaitMs() const {
    int worst = 0;
    for (const auto* c : active()) worst = std::max(worst, c->timingFor(c->profile).settle_wait_ms);
    return worst > 0 ? worst : CameraProfileTiming{}.settle_wait_ms;
}

int CameraConfig::maxFrameTimeoutMs() const {
    int worst = 0;
    for (const auto* c : active())
        worst = std::max(worst, c->timingFor(c->profile).frame_timeout_ms);
    return worst > 0 ? worst : CameraProfileTiming{}.frame_timeout_ms;
}

std::string NetworkConfig::brokerUri() const {
    // A scheme means the operator wrote the whole URI: hands off. Appending a port
    // could corrupt one that already has it, or a ws:// path.
    if (broker_ip.find("://") != std::string::npos) return broker_ip;

    std::string host = broker_ip;
    bool        has_port = false;
    if (!host.empty() && host.front() == '[') {          // bracketed IPv6
        const size_t close = host.rfind(']');
        has_port = close != std::string::npos && host.find(':', close) != std::string::npos;
    } else {
        const size_t colons = static_cast<size_t>(std::count(host.begin(), host.end(), ':'));
        if (colons == 1) {
            has_port = true;
        } else if (colons > 1) {
            host = "[" + host + "]";  // bare IPv6; bracket it so the port is unambiguous
        }
    }

    if (has_port) return "tcp://" + host;
    return "tcp://" + host + ":" + std::to_string(mqtt_port);
}

double AppConfig::image_rate() const {
    return general.image_interval > 0 ? 1.0 / general.image_interval : 0.0;
}

double TestProfile::get(const std::string& key, double fallback) const {
    auto it = params.find(key);
    return it != params.end() ? it->second : fallback;
}

int TestProfile::geti(const std::string& key, int fallback) const {
    auto it = params.find(key);
    return it != params.end() ? static_cast<int>(it->second) : fallback;
}

bool TestProfile::getBool(const std::string& key, bool fallback) const {
    auto it = text.find(key);
    if (it == text.end() || it->second.empty()) return fallback;
    const std::string& v = it->second;
    return v == "1" || v == "true" || v == "yes" || v == "on";
}

std::string TestProfile::gets(const std::string& key, const std::string& fallback) const {
    auto it = text.find(key);
    return (it != text.end() && !it->second.empty()) ? it->second : fallback;
}

std::vector<long> TestProfile::getLongList(const std::string& key) const {
    std::vector<long> out;
    auto it = text.find(key);
    if (it == text.end()) return out;
    std::stringstream ss(it->second);
    std::string tok;
    while (std::getline(ss, tok, ',')) {
        try { out.push_back(std::stol(tok)); } catch (...) {}
    }
    return out;
}

const TestProfile* TestConfig::find(const std::string& name) const {
    auto it = profiles.find(name);
    return it != profiles.end() ? &it->second : nullptr;
}

AppConfig ConfigLoader::fromMap(const std::map<std::string, std::string>& kv) {
    AppConfig cfg;

    cfg.general.tower_name     = get(kv, "General.tower_name", cfg.general.tower_name);
    cfg.general.image_interval = getDouble(kv, "General.image_interval", cfg.general.image_interval);
    cfg.general.debug          = getBool(kv, "General.debug", cfg.general.debug);

    // [Board] / [Hardware]: normally from hardware.ini, but read from the same
    // merged map, so a config.ini carrying them still works during migration.
    cfg.board.model        = get(kv, "Board.model", cfg.board.model);
    cfg.board.firmware_env = get(kv, "Board.firmware_env", cfg.board.firmware_env);

    cfg.hardware.axes    = splitList(get(kv, "Hardware.axes"));
    cfg.hardware.cameras = splitList(get(kv, "Hardware.cameras"));
    cfg.hardware.imu     = lowered(get(kv, "Hardware.imu"));
    cfg.hardware.env     = lowered(get(kv, "Hardware.env"));
    cfg.hardware.cooling = lowered(get(kv, "Hardware.cooling"));
    // The same rules the firmware build applies (firmware/tools/gen_wiring.py):
    // the fan is run from the DHT11's temperature, on the MCU.
    if (!cfg.hardware.cooling.empty() && cfg.hardware.cooling != "none" &&
        cfg.hardware.cooling != "fan")
        throw std::runtime_error("Hardware.cooling must be 'none' or 'fan' (got '" +
                                 cfg.hardware.cooling + "')");
    if (cfg.hardware.cooling == "fan" && cfg.hardware.env != "dht11")
        throw std::runtime_error("Hardware.cooling = fan needs Hardware.env = dht11: the fan "
                                 "is driven from the temperature the motor MCU reads");
    {
        auto& p = cfg.hardware.pins;
        p.yaw_cs   = getInt(kv, "Pins.yaw_cs", -1);
        p.yaw_en   = getInt(kv, "Pins.yaw_en", -1);
        p.pitch_cs = getInt(kv, "Pins.pitch_cs", -1);
        p.pitch_en = getInt(kv, "Pins.pitch_en", -1);
        p.spi_sck  = getInt(kv, "Pins.spi_sck", -1);
        p.spi_mosi = getInt(kv, "Pins.spi_mosi", -1);
        p.spi_miso = getInt(kv, "Pins.spi_miso", -1);
        p.dht         = getInt(kv, "Pins.dht", -1);
        p.fan_pwm     = getInt(kv, "Pins.fan_pwm", -1);
        p.fan_tach    = getInt(kv, "Pins.fan_tach", -1);
        p.spi_idle_cs = getInt(kv, "Pins.spi_idle_cs", -1);
    }
    if (kv.count("Hardware.pan_step_deg")) {
        cfg.hardware.pan_step_deg = getDouble(kv, "Hardware.pan_step_deg", 0.0);
        if (!(cfg.hardware.pan_step_deg > 0.0))
            throw std::runtime_error("Hardware.pan_step_deg must be > 0 (degrees of bearing "
                                     "one picture covers)");
    }
    cfg.hardware.save_workers   = getInt(kv, "Hardware.save_workers", cfg.hardware.save_workers);
    cfg.hardware.jxl_threads    = getInt(kv, "Hardware.jxl_threads", cfg.hardware.jxl_threads);
    cfg.hardware.save_queue_max = getInt(kv, "Hardware.save_queue_max", cfg.hardware.save_queue_max);
    if (cfg.hardware.save_workers < 1 || cfg.hardware.save_workers > 4)
        throw std::runtime_error("Hardware.save_workers must be in 1..4 (the boards have 4 cores)");
    if (cfg.hardware.jxl_threads < 0 || cfg.hardware.jxl_threads > 8)
        throw std::runtime_error("Hardware.jxl_threads must be in 0..8 (0 = 4 / save_workers)");
    if (cfg.hardware.jxl_threads == 0)
        cfg.hardware.jxl_threads = std::max(1, 4 / cfg.hardware.save_workers);
    if (cfg.hardware.save_queue_max < 1 || cfg.hardware.save_queue_max > 32)
        throw std::runtime_error("Hardware.save_queue_max must be in 1..32 (each raw frame "
                                 "waiting holds ~24 MB)");
    for (const auto& a : cfg.hardware.axes)
        if (a != "yaw" && a != "pitch")
            throw std::runtime_error("Hardware.axes: unknown axis '" + a +
                                     "' (expected yaw and/or pitch)");

    cfg.network.broker_ip = get(kv, "Network.zkms_server_ip", cfg.network.broker_ip);
    cfg.network.mqtt_port = getInt(kv, "Network.mqtt_port", cfg.network.mqtt_port);
    if (cfg.network.mqtt_port < 1 || cfg.network.mqtt_port > 65535)
        throw std::runtime_error("Network.mqtt_port must be in 1..65535");
    // Secrets: environment variables win over the file.
    cfg.network.mqtt_user = envOr("FGC_MQTT_USER", get(kv, "Network.mqtt_user"));
    cfg.network.mqtt_pw   = envOr("FGC_MQTT_PW", get(kv, "Network.mqtt_pw"));

    cfg.serial.device = get(kv, "Serial.device", cfg.serial.device);
    cfg.serial.baud   = static_cast<unsigned>(getInt(kv, "Serial.baud", cfg.serial.baud));

    // ---- [Camera] shared defaults, then one [Camera.<name>] block per camera ----
    cfg.camera.jxl_distance = getDouble(kv, "Camera.jxl_distance", cfg.camera.jxl_distance);
    cfg.camera.jxl_effort   = getInt(kv, "Camera.jxl_effort", cfg.camera.jxl_effort);
    cfg.camera.demosaic     = lowered(get(kv, "Camera.demosaic", cfg.camera.demosaic));

    // Cameras are discovered from the key names rather than a list, so there is
    // no registry to keep in sync: "Camera.rgb.id" declares a camera called rgb.
    // A third dotted segment ("Camera.rgb.standard.settle_wait_ms") is per-profile
    // timing, so only two-segment suffixes name a camera.
    std::vector<std::string> names;      // in first-seen order
    for (const auto& [key, unused] : kv) {
        (void)unused;
        if (key.rfind("Camera.", 0) != 0) continue;
        const std::string rest = key.substr(7);
        const auto dot = rest.find('.');
        if (dot == std::string::npos) continue;                     // [Camera] itself
        const std::string name = rest.substr(0, dot);
        if (rest.find('.', dot + 1) != std::string::npos) {         // per-profile timing
            if (std::find(names.begin(), names.end(), name) == names.end()) names.push_back(name);
            continue;
        }
        if (std::find(names.begin(), names.end(), name) == names.end()) names.push_back(name);
    }

    cfg.camera.cameras.clear();
    for (const auto& name : names) {
        const std::string pre = "Camera." + name + ".";
        CameraSpec c;
        c.name         = name;
        c.enabled      = getBool(kv, pre + "enabled", true);
        c.driver       = get(kv, pre + "driver", c.driver);
        c.id           = get(kv, pre + "id");
        c.label        = get(kv, pre + "label", name);
        c.profile_dir  = get(kv, pre + "profile_dir");
        c.profile      = get(kv, pre + "profile", c.profile);
        c.rotation_deg = getInt(kv, pre + "rotation_deg", c.rotation_deg);
        c.jxl_distance = getDouble(kv, pre + "jxl_distance", cfg.camera.jxl_distance);
        c.jxl_effort   = getInt(kv, pre + "jxl_effort", cfg.camera.jxl_effort);
        c.demosaic     = lowered(get(kv, pre + "demosaic", cfg.camera.demosaic));

        // Per-profile timing: Camera.<name>.<profile>.settle_wait_ms
        for (const auto& [key, val] : kv) {
            (void)val;
            if (key.rfind(pre, 0) != 0) continue;
            const std::string rest = key.substr(pre.size());
            const auto dot = rest.find('.');
            if (dot == std::string::npos) continue;
            const std::string profile = rest.substr(0, dot);
            const std::string field   = rest.substr(dot + 1);
            CameraProfileTiming& t = c.timing[profile];
            if (field == "settle_wait_ms")        t.settle_wait_ms   = getInt(kv, key, t.settle_wait_ms);
            else if (field == "frame_timeout_ms") t.frame_timeout_ms = getInt(kv, key, t.frame_timeout_ms);
            else if (field == "settle_rule")      t.settle_rule      = lowered(get(kv, key));
            else throw std::runtime_error("unknown key '" + key + "' (expected " + pre + profile +
                                          ".settle_wait_ms, .frame_timeout_ms or .settle_rule)");
            if (t.settle_rule != "fixed" && t.settle_rule != "brightness")
                throw std::runtime_error(key.substr(0, key.rfind('.')) + ".settle_rule must be "
                                         "'fixed' or 'brightness'");
        }

        if (c.driver != "vimba")
            throw std::runtime_error("Camera." + name + ".driver must be 'vimba' (got '" +
                                     c.driver + "'); no other backend is implemented yet");
        if (c.enabled && c.id.empty())
            throw std::runtime_error("Camera." + name + ".id is required (USB DEV_ id or GigE IP)");
        if (c.profile_dir.empty())
            throw std::runtime_error("Camera." + name + ".profile_dir is required");
        if (c.jxl_distance < 0.0)
            throw std::runtime_error("Camera." + name + ".jxl_distance must be >= 0 (0 = lossless)");
        if (c.jxl_effort < 1 || c.jxl_effort > 9)
            throw std::runtime_error("Camera." + name + ".jxl_effort must be in 1..9");
        if (c.demosaic != "edge_aware" && c.demosaic != "bilinear")
            throw std::runtime_error("Camera." + name + ".demosaic must be 'edge_aware' or "
                                     "'bilinear' (got '" + c.demosaic + "')");
        if (c.rotation_deg != 0 && c.rotation_deg != 90 && c.rotation_deg != 180 &&
            c.rotation_deg != 270)
            throw std::runtime_error("Camera." + name + ".rotation_deg must be 0, 90, 180 or 270");
        for (const auto& [pname, t] : c.timing) {
            if (t.settle_wait_ms < 0 || t.frame_timeout_ms < 0)
                throw std::runtime_error("Camera." + name + "." + pname +
                                         " timings must be >= 0");
        }
        cfg.camera.cameras.push_back(std::move(c));
    }

    std::string out = get(kv, "Paths.output_dir");
    cfg.paths.output_dir = out.empty() ? paths::defaultOutputDir() : paths::expandUser(out);

    cfg.features.enable_mqtt   = getBool(kv, "Features.enable_mqtt", cfg.features.enable_mqtt);
    cfg.features.enable_camera = getBool(kv, "Features.enable_camera", cfg.features.enable_camera);
    cfg.features.enable_serial = getBool(kv, "Features.enable_serial", cfg.features.enable_serial);
    cfg.features.enable_imu    = getBool(kv, "Features.enable_imu", cfg.features.enable_imu);
    cfg.features.mock_camera   = getBool(kv, "Features.mock_camera", cfg.features.mock_camera);
    cfg.features.mock_serial   = getBool(kv, "Features.mock_serial", cfg.features.mock_serial);
    cfg.features.mock_imu      = getBool(kv, "Features.mock_imu", cfg.features.mock_imu);
    cfg.features.enable_env    = getBool(kv, "Features.enable_env", cfg.features.enable_env);
    cfg.features.mock_env      = getBool(kv, "Features.mock_env", cfg.features.mock_env);
    cfg.features.mock_needcfg  = getBool(kv, "Features.mock_needcfg", cfg.features.mock_needcfg);
    cfg.features.strict_presence =
        getBool(kv, "Features.strict_presence", cfg.features.strict_presence);

    // [Hardware] imu / env are the declaration; enable_imu / enable_env are the
    // older flags that said it a second time. Resolve them into one answer here,
    // once, so nothing downstream has to know there were ever two keys - and so a
    // rig cannot declare a sensor and then be told it is disabled.
    {
        auto settle = [&](const char* what, const std::string& declared, const char* flag_key,
                          bool& out) {
            const SensorEnable e =
                resolveSensorEnable(declared, out, kv.count(flag_key) > 0);
            if (e.conflict)
                LOG_WARN << "[Hardware] " << what << " = '" << declared << "' and [" << flag_key
                         << "] disagree; the declaration wins (" << what << " "
                         << (e.enabled ? "enabled" : "disabled")
                         << ") -- delete the flag, it is what hardware.ini is for";
            else if (e.source == SensorEnableSource::Declaration && kv.count(flag_key))
                LOG_INFO << "[" << flag_key << "] is redundant: [Hardware] " << what
                         << " already declares it";
            out = e.enabled;
        };
        settle("imu", cfg.hardware.imu, "Features.enable_imu", cfg.features.enable_imu);
        settle("env", cfg.hardware.env, "Features.enable_env", cfg.features.enable_env);
    }

    cfg.imu.device = get(kv, "IMU.device", cfg.imu.device);
    cfg.imu.baud   = static_cast<unsigned>(getInt(kv, "IMU.baud", cfg.imu.baud));

    // [IMU] x/y/z: how the unit is bolted on, in degrees about forward/right/down.
    // A value outside +/-360 is a typo far more often than an intent, and one that
    // is accepted silently is invisible afterwards - the readings just quietly
    // describe the wrong axes.
    cfg.imu.mount.x_deg = getDouble(kv, "IMU.x", cfg.imu.mount.x_deg);
    cfg.imu.mount.y_deg = getDouble(kv, "IMU.y", cfg.imu.mount.y_deg);
    cfg.imu.mount.z_deg = getDouble(kv, "IMU.z", cfg.imu.mount.z_deg);
    for (const auto& [axis, value] : {std::pair{"x", cfg.imu.mount.x_deg},
                                      std::pair{"y", cfg.imu.mount.y_deg},
                                      std::pair{"z", cfg.imu.mount.z_deg}}) {
        if (!std::isfinite(value) || std::abs(value) > 360.0)
            throw std::runtime_error(std::string("IMU.") + axis +
                                     " must be a rotation in degrees within +/-360");
    }

    cfg.env.i2c_device = get(kv, "Env.i2c_device", cfg.env.i2c_device);
    cfg.env.i2c_addr   = static_cast<unsigned>(
        getIntAutoBase(kv, "Env.i2c_addr", static_cast<int>(cfg.env.i2c_addr)));
    cfg.env.period_ms  = getInt(kv, "Env.period_ms", cfg.env.period_ms);

    // [Test] + [TestProfile.<name>]: discover profiles by scanning the flattened
    // keys. inih gives us "TestProfile.<name>.<key>" => value; every numeric value
    // lands in that profile's open param map for the test modules to read.
    cfg.test.default_profile = get(kv, "Test.profile", cfg.test.default_profile);
    cfg.test.baseline_file   = get(kv, "Test.baseline_file");
    cfg.test.usbfs_min_mb    = getInt(kv, "Test.usbfs_min_mb", cfg.test.usbfs_min_mb);
    cfg.test.usb3_lpm_path   = get(kv, "Test.usb3_lpm_path");
    if (!cfg.test.baseline_file.empty())
        cfg.test.baseline_file = paths::expandUser(cfg.test.baseline_file);
    {
        const std::string prefix = "TestProfile.";
        for (const auto& [key, val] : kv) {
            if (key.rfind(prefix, 0) != 0) continue;
            auto dot = key.find('.', prefix.size());
            if (dot == std::string::npos) continue;
            std::string pname = key.substr(prefix.size(), dot - prefix.size());
            std::string pkey  = key.substr(dot + 1);
            if (pname.empty() || pkey.empty() || val.empty()) continue;
            auto& prof = cfg.test.profiles[pname];
            prof.name = pname;
            prof.text[pkey] = val;                 // raw string (covers comma lists)
            try {
                prof.params[pkey] = std::stod(val);  // also numeric where possible
            } catch (...) {
                // list/non-numeric value: the raw string in `text` is what modules read
            }
        }
    }

    cfg.logging.level = get(kv, "Logging.level", cfg.logging.level);
    cfg.logging.trace = get(kv, "Logging.trace", cfg.logging.trace);
    cfg.logging.file        = getBool(kv, "Logging.file", cfg.logging.file);
    cfg.logging.file_level  = get(kv, "Logging.file_level", cfg.logging.file_level);
    cfg.logging.file_max_mb = getInt(kv, "Logging.file_max_mb", cfg.logging.file_max_mb);
    cfg.logging.file_keep   = getInt(kv, "Logging.file_keep", cfg.logging.file_keep);
    cfg.logging.file_dir    = get(kv, "Logging.file_dir", cfg.logging.file_dir);
    // Clamp rather than refuse: a silly retention value should not stop a tower
    // starting, but it must not be obeyed either. A max_mb under 1 would rotate
    // on almost every line.
    if (cfg.logging.file_max_mb < 1)    cfg.logging.file_max_mb = 1;
    if (cfg.logging.file_max_mb > 1024) cfg.logging.file_max_mb = 1024;
    if (cfg.logging.file_keep < 1)      cfg.logging.file_keep = 1;
    if (cfg.logging.file_keep > 100)    cfg.logging.file_keep = 100;

    cfg.ui.enable_tui = getBool(kv, "UI.enable_tui", cfg.ui.enable_tui);

    cfg.startup.home = getBool(kv, "Startup.home", cfg.startup.home);
    if (auto it = kv.find("Startup.mode"); it != kv.end() && !it->second.empty()) {
        if (it->second == "manual")    cfg.startup.mode = Mode::Manual;
        else if (it->second == "auto") cfg.startup.mode = Mode::Auto;
        else
            throw std::runtime_error("Config key 'Startup.mode' must be manual or auto, got '" +
                                     it->second + "'" +
                                     (it->second == "pan" ? " (pan is chosen by command: "
                                                            "`mode pan <heading> <span>`)"
                                                          : ""));
    }

    // [Motor]: the degrees<->counts maps, anchored on the homed mechanical centre
    // (see Geometry). min_deg/max_deg are NOT configured - they are derived from
    // the firmware's homed soft limits, the only place they can be correct.
    cfg.geometry.yaw.counts_per_deg   = getDouble(kv, "Motor.yaw_counts_per_deg", cfg.geometry.yaw.counts_per_deg);
    cfg.geometry.yaw.center_count     = getLong(kv, "Motor.yaw_center_count", cfg.geometry.yaw.center_count);
    cfg.geometry.yaw.deg_at_center    = getDouble(kv, "Motor.yaw_heading_at_center", cfg.geometry.yaw.deg_at_center);
    cfg.geometry.pitch.counts_per_deg = getDouble(kv, "Motor.pitch_counts_per_deg", cfg.geometry.pitch.counts_per_deg);
    cfg.geometry.pitch.center_count   = getLong(kv, "Motor.pitch_center_count", cfg.geometry.pitch.center_count);
    cfg.geometry.pitch.deg_at_center  = getDouble(kv, "Motor.pitch_angle_at_center", cfg.geometry.pitch.deg_at_center);
    cfg.yaw_soft_margin_counts   = getLong(kv, "Motor.yaw_soft_margin_counts", cfg.yaw_soft_margin_counts);
    cfg.pitch_soft_margin_counts = getLong(kv, "Motor.pitch_soft_margin_counts", cfg.pitch_soft_margin_counts);
    cfg.enc_error_warn_counts = getLong(kv, "Motor.enc_error_warn_counts",
                                        cfg.enc_error_warn_counts);
    cfg.homing_timeout_s = getInt(kv, "Motor.homing_timeout_s", cfg.homing_timeout_s);

    // [Motor.<axis>]: this tower's drivetrain, normally from hardware.ini. Note
    // the section is DOTTED - these are deliberately different keys from the flat
    // [Motor] ones above, because hardware.ini is merged over config.ini and
    // wins, so a shared key would silently discard the calibration that the save
    // path writes back to config.ini.
    auto axisDrivetrain = [&kv](const char* axis, AxisDrivetrainConfig& d) {
        const std::string pre = std::string("Motor.") + axis + ".";
        for (const auto& [k, v] : kv) {
            (void)v;
            if (k.rfind(pre, 0) == 0) { d.declared = true; break; }
        }
        d.r_sense_ohm       = getDouble(kv, pre + "r_sense_ohm", d.r_sense_ohm);
        d.run_current_ma    = getDouble(kv, pre + "run_current_ma", d.run_current_ma);
        // An axis that names only a run current is not asking for a reduction.
        d.homing_current_ma = getDouble(kv, pre + "homing_current_ma", d.run_current_ma);
        d.travel_deg        = getDouble(kv, pre + "travel_deg", d.travel_deg);
        d.scan_speed_deg_s  = getDouble(kv, pre + "scan_speed_deg_s", d.scan_speed_deg_s);
        d.homing_speed_deg_s = getDouble(kv, pre + "homing_speed_deg_s", d.homing_speed_deg_s);
        d.center_speed_deg_s = getDouble(kv, pre + "center_speed_deg_s", d.center_speed_deg_s);
        d.steps_per_rev      = getInt(kv, pre + "steps_per_rev", static_cast<int>(d.steps_per_rev));
        d.enc_deviation      = getInt(kv, pre + "enc_deviation", static_cast<int>(d.enc_deviation));
        d.enc_const          = getDouble(kv, pre + "enc_const", d.enc_const);
        d.wiring_declared    = kv.count(pre + "sw_mode") || kv.count(pre + "has_encoder");
        d.sw_mode     = static_cast<unsigned>(getInt(kv, pre + "sw_mode", static_cast<int>(d.sw_mode)));
        d.has_encoder = getBool(kv, pre + "has_encoder", d.has_encoder);
    };
    axisDrivetrain("yaw", cfg.drivetrain.yaw);
    axisDrivetrain("pitch", cfg.drivetrain.pitch);

    // [Scan]: the scan-grid CSV. No file, no auto-sweep - nothing is generated.
    cfg.scan.grid_file = get(kv, "Scan.grid_file", cfg.scan.grid_file);

    // ---- validation ----
    if (!(cfg.general.image_interval > 0) || !std::isfinite(cfg.general.image_interval))
        throw std::runtime_error("General.image_interval must be > 0 (got " +
                                 get(kv, "General.image_interval") + ")");
    if (cfg.serial.baud == 0)
        throw std::runtime_error("Serial.baud must be > 0");

    // A zero scale makes every degree map to the centre and every count read back
    // as the centre - the axis would look calibrated and point nowhere.
    if (std::abs(cfg.geometry.yaw.counts_per_deg) < 1e-9)
        throw std::runtime_error("Motor.yaw_counts_per_deg must be non-zero");
    if (std::abs(cfg.geometry.pitch.counts_per_deg) < 1e-9)
        throw std::runtime_error("Motor.pitch_counts_per_deg must be non-zero");
    // The centre count exists so the whole working range stays positive; a
    // non-positive one defeats the point and can drive the firmware negative.
    if (cfg.geometry.yaw.center_count <= 0)
        throw std::runtime_error("Motor.yaw_center_count must be > 0");
    if (cfg.geometry.pitch.center_count <= 0)
        throw std::runtime_error("Motor.pitch_center_count must be > 0");
    if (cfg.yaw_soft_margin_counts < 0)
        throw std::runtime_error("Motor.yaw_soft_margin_counts must be >= 0");
    if (cfg.pitch_soft_margin_counts < 0)
        throw std::runtime_error("Motor.pitch_soft_margin_counts must be >= 0");
    if (cfg.homing_timeout_s <= 0)
        throw std::runtime_error("Motor.homing_timeout_s must be > 0");

    // [Motor.<axis>]. Currents are only meaningful alongside the sense resistor
    // that scales them, and a current without one would be computed against a
    // guess - so demand them together rather than inventing a default resistor.
    auto checkDrivetrain = [](const char* axis, const AxisDrivetrainConfig& d) {
        const std::string sec = std::string("Motor.") + axis;
        if (d.run_current_ma > 0.0 && d.r_sense_ohm <= 0.0)
            throw std::runtime_error(sec + ".run_current_ma needs " + sec +
                                     ".r_sense_ohm (the sense resistor on that driver "
                                     "board) to mean anything");
        if (d.run_current_ma < 0.0 || d.homing_current_ma < 0.0)
            throw std::runtime_error(sec + " currents must be >= 0");
        if (d.travel_deg < 0.0 || d.travel_deg > 720.0)
            throw std::runtime_error(sec + ".travel_deg must be within (0, 720]; the "
                                           "direction of travel is carried by the sign of "
                                           "counts_per_deg, not by this angle");
        if (d.enc_const != 0.0 && !encConstRegister(d.enc_const))
            throw std::runtime_error(sec + ".enc_const must be between 0 and 32768 with at "
                                           "most 4 decimals (microsteps per encoder count; "
                                           "leave it out for the default 12.8)");
    };
    checkDrivetrain("yaw", cfg.drivetrain.yaw);
    checkDrivetrain("pitch", cfg.drivetrain.pitch);

    // Keys from the pre-centre-anchoring layout. Silently ignoring them would
    // leave an operator convinced they had configured a heading that is in fact
    // coming from somewhere else entirely - the exact failure this layout removes.
    static const char* kRemovedMotorKeys[] = {
        "Motor.yaw_zero_count",   "Motor.pitch_zero_count", "Motor.yaw_min_deg",
        "Motor.yaw_max_deg",      "Motor.pitch_min_deg",    "Motor.pitch_max_deg",
        "Motor.yaw_home_zero",
        // Drivetrain keys written under [Motor] instead of [Motor.<axis>]. They
        // flatten to a name nothing reads, so without this they would be ignored
        // in total silence - and an operator would believe they had reduced the
        // homing current when they had not.
        "Motor.r_sense_ohm",      "Motor.run_current_ma",
        "Motor.homing_current_ma", "Motor.travel_deg",
    };
    std::string stale;
    for (const char* k : kRemovedMotorKeys)
        if (kv.count(k)) stale += (stale.empty() ? "" : ", ") + std::string(k + 6);
    if (!stale.empty())
        LOG_WARN << "[Motor] ignoring keys nothing reads: " << stale
                 << " -- travel limits are derived from homing, the heading origin "
                    "comes from yaw_heading_at_center (set it with 'gimbal heading "
                    "setup'), and drivetrain keys belong under [Motor.yaw] / "
                    "[Motor.pitch], not [Motor]";

    // Keys from when a blank grid_file meant "generate a grid". The generator is
    // gone: the CSV is the only source. Ignoring these quietly would leave an
    // operator believing they had set the scan arc when nothing reads it.
    static const char* kRemovedScanKeys[] = {
        "Scan.yaw_intervals", "Scan.yaw_min_deg", "Scan.yaw_max_deg", "Scan.pitch_levels",
    };
    std::string stale_scan;
    for (const char* k : kRemovedScanKeys)
        if (kv.count(k)) stale_scan += (stale_scan.empty() ? "" : ", ") + std::string(k + 5);
    if (!stale_scan.empty())
        LOG_WARN << "[Scan] ignoring keys nothing reads: " << stale_scan
                 << " -- grids are no longer generated; list the waypoints in the "
                    "grid_file CSV instead";

    return cfg;
}

SensorEnable resolveSensorEnable(const std::string& declared, bool flag_value, bool flag_present) {
    SensorEnable r;
    if (declared.empty()) {
        // Nothing stated, so the legacy flag still governs. This is every tower
        // that has not been migrated, and it must behave exactly as before.
        r.enabled = flag_value;
        r.source  = flag_present ? SensorEnableSource::Flag : SensorEnableSource::Default;
        return r;
    }
    r.enabled  = (declared != "none");
    r.source   = SensorEnableSource::Declaration;
    r.conflict = flag_present && (flag_value != r.enabled);
    return r;
}

bool HardwareConfig::hasAxis(const std::string& name) const {
    // An undeclared rig answers true for everything - see the header.
    if (axes.empty()) return true;
    return std::find(axes.begin(), axes.end(), name) != axes.end();
}

std::string HardwareConfig::axesLabel() const {
    std::string s;
    for (const auto& a : axes) s += (s.empty() ? "" : ", ") + a;
    return s;
}

AppConfig ConfigLoader::loadFromFile(const std::string& path, const std::string& hardware_path) {
    std::map<std::string, std::string> kv;
    int rc = ini_parse(path.c_str(), iniHandler, &kv);
    if (rc < 0) throw std::runtime_error("Cannot read config file: " + path);
    if (rc > 0)
        throw std::runtime_error("Parse error in config file " + path + " at line " +
                                 std::to_string(rc));

    // hardware.ini is layered ON TOP, so the assembly description wins over a
    // config.ini that still carries the same keys from before the split. Any such
    // leftover is named once, because it is a migration leftover to delete rather
    // than a setting that is quietly doing nothing.
    std::vector<std::string> shadowed;
    if (!hardware_path.empty()) {
        std::map<std::string, std::string> hw;
        int hrc = ini_parse(hardware_path.c_str(), iniHandler, &hw);
        if (hrc < 0) throw std::runtime_error("Cannot read hardware file: " + hardware_path);
        if (hrc > 0)
            throw std::runtime_error("Parse error in hardware file " + hardware_path +
                                     " at line " + std::to_string(hrc));
        for (const auto& [k, v] : hw) {
            if (auto it = kv.find(k); it != kv.end() && it->second != v) shadowed.push_back(k);
            kv[k] = v;
        }
    }

    AppConfig cfg = fromMap(kv);

    if (!hardware_path.empty()) {
        cfg.hardware.declared    = true;
        cfg.hardware.source_path = hardware_path;
        LOG_INFO << "hardware: " << hardware_path
                 << (cfg.board.model.empty() ? "" : "  board " + cfg.board.model)
                 << (cfg.hardware.axes.empty() ? "" : "  axes " + cfg.hardware.axesLabel());
        for (const auto& k : shadowed)
            LOG_WARN << "config.ini still sets " << k
                     << ", which hardware.ini overrides -- delete it from config.ini";
    }
    // Anchor a relative scan grid_file to the config file's directory so it resolves
    // no matter which working directory the process is launched from (the config
    // itself is found via a search path that may be unrelated to the cwd).
    if (!cfg.scan.grid_file.empty()) {
        std::filesystem::path gf(paths::expandUser(cfg.scan.grid_file));
        if (gf.is_relative()) gf = std::filesystem::path(path).parent_path() / gf;
        cfg.scan.grid_file = gf.lexically_normal().string();
    }
    // Same for each camera's profile directory.
    for (auto& c : cfg.camera.cameras) {
        std::filesystem::path pd(paths::expandUser(c.profile_dir));
        if (pd.is_relative()) pd = std::filesystem::path(path).parent_path() / pd;
        c.profile_dir = pd.lexically_normal().string();
    }
    return cfg;
}

namespace {
std::string trimmed(const std::string& s) {
    const char* ws = " \t\r\n";
    size_t a = s.find_first_not_of(ws);
    if (a == std::string::npos) return "";
    size_t b = s.find_last_not_of(ws);
    return s.substr(a, b - a + 1);
}

// Marker for a superseded value, kept so a calibration can be reverted by hand.
// It is a comment, so inih ignores it on the next read, but it is distinctive
// enough for updateIniSectionKeys to find its own earlier markers and replace
// them rather than pile them up.
const std::string kPrevMarker = ";prev ";

// The value inih would actually parse from the right-hand side of `key = value`:
// everything up to an inline comment, which is a ';' PRECEDED BY WHITESPACE (see
// ini_find_chars_or_comment in ini.c, with INI_ALLOW_INLINE_COMMENTS=1 and
// INI_INLINE_COMMENT_PREFIXES=";"). Mirroring that rule matters here: "did this
// value change?" has to compare what the program read, not the raw line, or a
// key carrying a trailing comment would look changed on every save.
// Do these two INI values denote the same NUMBER, however they are spelled?
//
// The history filter below compares what is in the file against what is about to
// be written, and the writer formats doubles with "%.10g" - so a hand-written
// "0.0" is rewritten as "0", and a plain string comparison calls that a change.
// It then records a ";prev" line whose "previous" value is the value it still
// has, stamped with the provenance of whatever save happened to be running.
//
// That is worse than cosmetic noise: ";prev" deliberately keeps exactly ONE
// generation, so a spurious entry DISPLACES the real previous value it exists to
// preserve, and attributes an untouched key to a calibration that never wrote it.
//
// Falls back to comparing text whenever either side is not a plain number, which
// is what keys like a device path need.
bool sameIniValue(const std::string& a, const std::string& b) {
    if (a == b) return true;
    auto asNumber = [](const std::string& s, double& out) {
        if (s.empty()) return false;
        char* end = nullptr;
        out       = std::strtod(s.c_str(), &end);
        if (end == s.c_str()) return false;          // nothing numeric at all
        while (*end && std::isspace(static_cast<unsigned char>(*end))) ++end;
        return *end == '\0';                         // trailing junk: not a number
    };
    double x = 0.0, y = 0.0;
    return asNumber(a, x) && asNumber(b, y) && x == y;
}

std::string iniValueOf(const std::string& rhs) {
    bool was_space = false;
    for (size_t i = 0; i < rhs.size(); ++i) {
        if (was_space && rhs[i] == ';') return trimmed(rhs.substr(0, i));
        was_space = std::isspace(static_cast<unsigned char>(rhs[i])) != 0;
    }
    return trimmed(rhs);
}

// If `t` (already trimmed) is a ";prev <key> = ..." marker, return <key>, else "".
std::string prevMarkerKey(const std::string& t) {
    const size_t n = kPrevMarker.size();
    if (t.compare(0, n, kPrevMarker) != 0) return "";
    const size_t eq = t.find('=', n);
    if (eq == std::string::npos) return "";
    return trimmed(t.substr(n, eq - n));
}
}  // namespace

std::string updateIniSectionKeys(const std::string& contents, const std::string& section,
                                 const std::vector<std::pair<std::string, std::string>>& kv,
                                 const std::string& provenance) {
    // Which keys are actually changing, and what they hold now.
    //
    // Only a changing key gets a ";prev" line, and only its marker is replaced:
    // a key whose value is unchanged keeps the history it has, because that still
    // names the value before the current one. This also keeps the file from
    // growing on every save - saveMotorGeometry rewrites all eight keys each time,
    // and without this filter seven of them would be noise.
    //
    // Computed in a first pass because a key's ";prev" marker sits ABOVE its value
    // line, so the writing pass meets the marker before it has seen whether the
    // value differs.
    std::vector<bool>        changed(kv.size(), false);
    std::vector<std::string> old_value(kv.size());
    {
        std::istringstream scan(contents);
        std::string        line, cur;
        std::vector<bool>  seen(kv.size(), false);
        while (std::getline(scan, line)) {
            const std::string t = trimmed(line);
            if (t.size() >= 2 && t.front() == '[' && t.back() == ']') {
                cur = trimmed(t.substr(1, t.size() - 2));
                continue;
            }
            if (cur != section || t.empty() || t[0] == ';' || t[0] == '#') continue;
            const size_t eq = line.find('=');
            if (eq == std::string::npos) continue;
            const std::string key = trimmed(line.substr(0, eq));
            for (size_t i = 0; i < kv.size(); ++i) {
                if (!seen[i] && key == kv[i].first) {
                    seen[i]      = true;
                    old_value[i] = iniValueOf(line.substr(eq + 1));
                    changed[i]   = !sameIniValue(old_value[i], kv[i].second);
                    break;
                }
            }
        }
    }
    const bool keep_history = !provenance.empty();

    std::vector<bool> written(kv.size(), false);
    std::istringstream in(contents);
    std::ostringstream out;
    std::string line, cur;
    while (std::getline(in, line)) {
        const std::string t = trimmed(line);
        if (t.size() >= 2 && t.front() == '[' && t.back() == ']') {
            cur = trimmed(t.substr(1, t.size() - 2));
        } else if (cur == section) {
            // An earlier ";prev" for a key that is changing now is dropped here
            // and re-emitted below, so exactly one generation is ever kept.
            const std::string pk = prevMarkerKey(t);
            if (!pk.empty()) {
                bool supersede = false;
                for (size_t i = 0; i < kv.size(); ++i)
                    if (pk == kv[i].first && changed[i]) { supersede = true; break; }
                if (supersede) continue;
            } else if (!t.empty() && t[0] != ';' && t[0] != '#') {
                const size_t eq = line.find('=');
                if (eq != std::string::npos) {
                    const std::string key = trimmed(line.substr(0, eq));
                    for (size_t i = 0; i < kv.size(); ++i) {
                        if (!written[i] && key == kv[i].first) {
                            if (keep_history && changed[i])
                                out << kPrevMarker << kv[i].first << " = " << old_value[i]
                                    << "   ; " << provenance << "\n";
                            line = kv[i].first + " = " + kv[i].second;
                            written[i] = true;
                            break;
                        }
                    }
                }
            }
        }
        out << line << "\n";
    }
    // Keys the section does not have yet go INTO it, after its last key line, with
    // a note of when and why. A second [section] block at the end reads the same
    // (inih merges duplicates) but is not where a person reading the file looks -
    // on tower 111 it left `cooling` a hundred lines away from `env`. Only a
    // section the file lacks altogether is appended.
    bool missing = false;
    for (bool w : written) missing = missing || !w;
    if (!missing) return out.str();

    std::vector<std::string> block;
    if (keep_history) block.push_back("; added   ; " + provenance);
    for (size_t i = 0; i < kv.size(); ++i)
        if (!written[i]) block.push_back(kv[i].first + " = " + kv[i].second);

    std::vector<std::string> lines;
    {
        std::istringstream split(out.str());
        for (std::string l; std::getline(split, l);) lines.push_back(l);
    }
    long header = -1, last_key = -1;
    for (size_t i = 0; i < lines.size(); ++i) {
        const std::string t = trimmed(lines[i]);
        if (t.size() >= 2 && t.front() == '[' && t.back() == ']') {
            if (header >= 0) break;   // the end of the first block of this section
            if (trimmed(t.substr(1, t.size() - 2)) == section) header = static_cast<long>(i);
            continue;
        }
        if (header >= 0 && !t.empty() && t[0] != ';' && t[0] != '#' &&
            t.find('=') != std::string::npos)
            last_key = static_cast<long>(i);
    }
    std::ostringstream res;
    if (header < 0) {
        res << out.str() << "\n[" << section << "]\n";
        for (const auto& b : block) res << b << "\n";
        return res.str();
    }
    const long after = last_key >= 0 ? last_key : header;
    for (size_t i = 0; i < lines.size(); ++i) {
        res << lines[i] << "\n";
        if (static_cast<long>(i) == after)
            for (const auto& b : block) res << b << "\n";
    }
    return res.str();
}

bool saveMotorGeometry(const std::string& path, const Geometry& geo, long yaw_margin,
                       long pitch_margin, const std::string& provenance) {
    if (path.empty()) return false;
    std::ifstream f(path);
    if (!f) return false;
    std::stringstream buf;
    buf << f.rdbuf();
    f.close();

    auto num = [](double v) {
        char b[32];
        std::snprintf(b, sizeof(b), "%.10g", v);
        return std::string(b);
    };
    // The whole [Motor] block, so it stays complete and self-consistent rather
    // than depending on which lines happened to be there already. min_deg/max_deg
    // are deliberately absent: they are derived from homing, not configured.
    const std::vector<std::pair<std::string, std::string>> kv = {
        {"yaw_counts_per_deg", num(geo.yaw.counts_per_deg)},
        {"yaw_center_count", std::to_string(geo.yaw.center_count)},
        {"yaw_heading_at_center", num(geo.yaw.deg_at_center)},
        {"yaw_soft_margin_counts", std::to_string(yaw_margin)},
        {"pitch_counts_per_deg", num(geo.pitch.counts_per_deg)},
        {"pitch_center_count", std::to_string(geo.pitch.center_count)},
        {"pitch_angle_at_center", num(geo.pitch.deg_at_center)},
        {"pitch_soft_margin_counts", std::to_string(pitch_margin)},
    };
    const std::string updated = updateIniSectionKeys(buf.str(), "Motor", kv, provenance);

    // Write a sibling temp file and rename over the original: a truncating write
    // that dies partway leaves config.ini destroyed, and three commands rewrite
    // this file while the program is running.
    std::error_code       ec;
    const fs::path        target(path);
    const fs::path        tmp = target.parent_path() / (target.filename().string() + ".tmp");
    {
        std::ofstream out(tmp, std::ios::trunc | std::ios::binary);
        if (!out) return false;
        out << updated;
        out.flush();
        if (!out) {
            fs::remove(tmp, ec);
            return false;
        }
    }
    fs::rename(tmp, target, ec);
    if (ec) {
        fs::remove(tmp, ec);
        return false;
    }
    return true;
}

}  // namespace fgc