#include <chrono>
#include <cstdio>
#include <filesystem>
#include <iostream>
#include <thread>

#include "betaflight.h"
#include "cli.h"
#include "eject.h"
#include "mounts.h"
#include "naming.h"
#include "serial.h"

namespace fs = std::filesystem;
using namespace bfebbx;

namespace {

const char* kUsage =
    "usage: bfebbx [--port PORT] [--output DIR] [--craft-name NAME] "
    "[--timeout SEC] [-v]\n";

// Exit codes (documented in README).
enum Exit {
    OK = 0,
    NO_PORT = 2,
    AMBIGUOUS_PORT = 3,
    SERIAL_FAIL = 4,
    VOLUME_TIMEOUT = 5,
    FILE_MISSING = 6,
    COPY_FAIL = 7,
    DEST_EXISTS = 8,
    USAGE = 64,
};

std::string resolvePort(const Options& opt) {
    if (!opt.port.empty()) return opt.port;
    auto ports = scanPorts("/dev", defaultPortPrefix());
    if (ports.empty()) {
        std::cerr << "error: no Betaflight serial port found (looked for /dev/"
                  << defaultPortPrefix() << "*). Use --port.\n";
        std::exit(NO_PORT);
    }
    if (ports.size() > 1) {
        std::cerr << "error: multiple candidate ports; pass --port:\n";
        for (const auto& p : ports) std::cerr << "  " << p << "\n";
        std::exit(AMBIGUOUS_PORT);
    }
    return ports.front();
}

// Poll for a newly-mounted volume that contains btfl_all.bbl.
MountEntry waitForVolume(const std::vector<MountEntry>& before, int timeoutSec,
                         bool verbose) {
    using clock = std::chrono::steady_clock;
    auto deadline = clock::now() + std::chrono::seconds(timeoutSec);
    while (clock::now() < deadline) {
        auto added = diffMounts(before, listMounts());
        for (const auto& m : added) {
            fs::path candidate = fs::path(m.mountpoint) / "btfl_all.bbl";
            std::error_code ec;
            if (fs::exists(candidate, ec)) {
                if (verbose) std::cerr << "found volume: " << m.mountpoint << "\n";
                return m;
            }
        }
        std::this_thread::sleep_for(std::chrono::milliseconds(500));
    }
    std::cerr << "error: mass-storage volume did not appear within " << timeoutSec
              << "s (try --timeout).\n";
    std::exit(VOLUME_TIMEOUT);
}

}  // namespace

int main(int argc, char** argv) {
    Options opt;
    try {
        opt = parseArgs(argc, argv);
    } catch (const std::exception& e) {
        std::cerr << "error: " << e.what() << "\n" << kUsage;
        return USAGE;
    }
    if (opt.help) {
        std::cout << kUsage;
        return OK;
    }

    const std::string port = resolvePort(opt);
    if (opt.verbose) std::cerr << "port: " << port << "\n";

    // 1. Read craft_name over the CLI (before msc reboots the board).
    std::string craft = opt.craftName;
    try {
        Serial s = Serial::openPort(port, 115200);
        enterCli(s);
        auto name = getCraftName(s, std::chrono::milliseconds(2000));
        if (craft.empty() && name.has_value()) craft = name.value();

        // 2. Snapshot mounts, then trigger mass-storage mode.
        auto before = listMounts();
        if (opt.verbose) std::cerr << "entering mass-storage mode...\n";
        enterMsc(s);
        // Ensure the msc reboot trigger is actually transmitted before we
        // release the fd, since a non-blocking fd offers no such guarantee.
        s.drain();
        // Serial port goes away as the FC reboots; drop it before polling.
        s = Serial::fromFd(-1);

        // 3. Wait for the volume.
        MountEntry vol = waitForVolume(before, opt.timeoutSec, opt.verbose);

        // 4. Build destination name and copy.
        std::string sanitized = sanitizeCraftName(craft);
        if (sanitized.empty()) {
            sanitized = "betaflight";
            if (craft.empty()) {
                std::cerr << "warning: could not read craft_name; using '" << sanitized
                          << "'\n";
            }
        }
        std::string fname = buildFilename(sanitized, std::time(nullptr));
        fs::path dest = fs::path(opt.output) / fname;

        std::error_code ec;
        if (fs::exists(dest, ec)) {
            std::cerr << "error: destination already exists: " << dest << "\n";
            return DEST_EXISTS;
        }
        fs::path src = fs::path(vol.mountpoint) / "btfl_all.bbl";
        if (!fs::exists(src, ec)) {
            std::cerr << "error: btfl_all.bbl not found on " << vol.mountpoint
                      << " (leaving volume mounted).\n";
            return FILE_MISSING;
        }
        fs::copy_file(src, dest, ec);
        if (ec) {
            std::cerr << "error: copy failed: " << ec.message()
                      << " (leaving volume mounted).\n";
            return COPY_FAIL;
        }
        std::cout << "wrote " << dest << "\n";

        // 5. Eject on success.
        try {
            ejectVolume(vol);
            if (opt.verbose) std::cerr << "ejected " << vol.mountpoint << "\n";
        } catch (const std::exception& e) {
            std::cerr << "warning: eject failed: " << e.what()
                      << " (file already saved; unmount manually).\n";
        }
    } catch (const std::exception& e) {
        std::cerr << "error: " << e.what() << "\n";
        return SERIAL_FAIL;
    }
    return OK;
}