#include "audio/audio_downloader.h"

#include "db/database_manager.h"
#include "logger/logger.h"

#include <curl/curl.h>
#include <openssl/evp.h>

#include <cctype>
#include <cstdio>
#include <cstdlib>
#include <filesystem>
#include <sstream>
#include <unordered_map>
#include <unordered_set>
#include <vector>

namespace radiantwave::audio {

namespace {

constexpr const char* AUDIO_DIR_SUFFIX = "/.local/radiantwave/audio/";
constexpr const char* USER_AGENT = "RadiantWave-Kiosk/0.1";

std::string audioDir() {
    const char* home = std::getenv("HOME");
    return std::string(home && *home ? home : "/tmp") + AUDIO_DIR_SUFFIX;
}

// Strips the "*" binary-mode marker and any "./" prefixes md5sum emits.
std::string stripManifestPrefix(std::string name) {
    if (!name.empty() && name.front() == '*') name.erase(0, 1);
    while (name.compare(0, 2, "./") == 0) name.erase(0, 2);
    return name;
}

// Produces a friendly display name from a bare filename for legacy manifests
// that carry no display name.
std::string humanizeFilename(const std::string& filename) {
    std::string name = filename;
    size_t dot = name.rfind('.');
    if (dot != std::string::npos) name.erase(dot);
    for (char& c : name) {
        if (c == '_') c = ' ';
    }
    return name;
}

// Tokenizes a manifest line, honoring a single-quoted display name that may
// contain spaces.
std::vector<std::string> tokenizeManifestLine(const std::string& line) {
    std::vector<std::string> tokens;
    size_t i = 0;
    const size_t n = line.size();
    while (i < n) {
        while (i < n && std::isspace(static_cast<unsigned char>(line[i]))) ++i;
        if (i >= n) break;
        if (line[i] == '\'') {
            size_t close = line.find('\'', i + 1);
            if (close == std::string::npos) break;
            tokens.push_back(line.substr(i + 1, close - i - 1));
            i = close + 1;
        } else {
            size_t start = i;
            while (i < n && !std::isspace(static_cast<unsigned char>(line[i]))) ++i;
            tokens.push_back(line.substr(start, i - start));
        }
    }
    return tokens;
}

// ─── HTTP helpers (libcurl) ─────────────────────────────────────────────

bool httpGetString(const std::string& url, std::string& body) {
    CURL* curl = curl_easy_init();
    if (!curl) return false;

    curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 15L);
    curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 10L);
    curl_easy_setopt(curl, CURLOPT_USERAGENT, USER_AGENT);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, +[](char* ptr, size_t size, size_t nmemb, void* userdata) -> size_t {
        auto* out = static_cast<std::string*>(userdata);
        out->append(ptr, size * nmemb);
        return size * nmemb;
    });
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &body);

    CURLcode res = curl_easy_perform(curl);
    long status = 0;
    curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &status);
    curl_easy_cleanup(curl);

    return res == CURLE_OK && status >= 200 && status < 300;
}

bool httpGetFile(const std::string& url, const std::string& path) {
    CURL* curl = curl_easy_init();
    if (!curl) return false;

    std::FILE* f = std::fopen(path.c_str(), "wb");
    if (!f) {
        curl_easy_cleanup(curl);
        return false;
    }

    curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
    curl_easy_setopt(curl, CURLOPT_TIMEOUT, 120L);
    curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 15L);
    curl_easy_setopt(curl, CURLOPT_USERAGENT, USER_AGENT);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, +[](char* ptr, size_t size, size_t nmemb, void* userdata) -> size_t {
        return std::fwrite(ptr, size, nmemb, static_cast<std::FILE*>(userdata));
    });
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, f);

    CURLcode res = curl_easy_perform(curl);
    long status = 0;
    curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &status);
    curl_easy_cleanup(curl);

    std::fclose(f);

    return res == CURLE_OK && status >= 200 && status < 300;
}

} // anonymous namespace

// ─── Public pure helpers ────────────────────────────────────────────────

// Frequency value (Hz) -> internal solfeggio frequency id. Mirrors the id<->Hz
// relationships documented in DatabaseManager::seedColorPalettes.
int frequencyIdForHz(int hz) {
    switch (hz) {
        case 174:
        case 285: return 1;
        case 396: return 2;
        case 417: return 3;
        case 432: return 4;
        case 528: return 5;
        case 639: return 6;
        case 741: return 7;
        case 852: return 8;
        case 963: return 9;
        default: return 0;
    }
}

int hzFromFilename(const std::string& filename) {
    size_t i = 0;
    while (i < filename.size() && filename[i] >= '0' && filename[i] <= '9') ++i;
    if (i == 0) return 0;
    // The digits must be a frequency: "396Hz.wav", "14Hz_Binaural.wav".
    if (i + 2 <= filename.size() &&
        (filename[i] == 'H' || filename[i] == 'h') &&
        (filename[i + 1] == 'Z' || filename[i + 1] == 'z')) {
        int hz = 0;
        for (size_t d = 0; d < i; ++d) {
            hz = hz * 10 + (filename[d] - '0');
        }
        return hz;
    }
    return 0;
}

bool parseManifest(const std::string& text, std::vector<AudioManifestEntry>& out) {
    std::vector<AudioManifestEntry> result;
    std::istringstream stream(text);
    std::string line;
    while (std::getline(stream, line)) {
        size_t start = line.find_first_not_of(" \t\r\n");
        if (start == std::string::npos) continue;
        size_t end = line.find_last_not_of(" \t\r\n");
        line = line.substr(start, end - start + 1);
        if (line.empty() || line.front() == '#') continue;

        std::vector<std::string> tokens = tokenizeManifestLine(line);
        if (tokens.empty()) continue;

        AudioManifestEntry entry;
        if (tokens.size() == 4) {
            // Current format: <filename> '<display name>' <hz> <md5>
            entry.filename = stripManifestPrefix(tokens[0]);
            entry.display_name = tokens[1];
            entry.solfeggio_frequency_hz = std::atoi(tokens[2].c_str());
            entry.md5 = tokens[3];
            if (entry.filename.empty() || entry.md5.size() != 32) continue;
            // Tolerant parse: honor the Hz value only when it maps to a known
            // frequency (a transitional manifest may carry an id, a typo may
            // carry garbage); otherwise fall back to the Hz from the filename.
            if (frequencyIdForHz(entry.solfeggio_frequency_hz) == 0) {
                int fromFilename = hzFromFilename(entry.filename);
                if (fromFilename != 0) {
                    entry.solfeggio_frequency_hz = fromFilename;
                }
            }
            result.push_back(std::move(entry));
        } else if (tokens.size() == 2 && tokens[0].size() == 32) {
            // Legacy format: <md5>  <filename>
            entry.md5 = tokens[0];
            entry.filename = stripManifestPrefix(tokens[1]);
            entry.display_name = humanizeFilename(entry.filename);
            entry.solfeggio_frequency_hz = hzFromFilename(entry.filename);
            if (entry.filename.empty()) continue;
            result.push_back(std::move(entry));
        }
        // else: malformed line, skip
    }
    if (result.empty()) return false;
    out = std::move(result);
    return true;
}

std::string computeFileMd5(const std::string& path) {
    std::FILE* f = std::fopen(path.c_str(), "rb");
    if (!f) return std::string();

    EVP_MD_CTX* ctx = EVP_MD_CTX_new();
    if (!ctx) {
        std::fclose(f);
        return std::string();
    }
    if (EVP_DigestInit_ex(ctx, EVP_md5(), nullptr) != 1) {
        EVP_MD_CTX_free(ctx);
        std::fclose(f);
        return std::string();
    }

    unsigned char buf[8192];
    size_t n;
    while ((n = std::fread(buf, 1, sizeof(buf), f)) > 0) {
        if (EVP_DigestUpdate(ctx, buf, n) != 1) {
            EVP_MD_CTX_free(ctx);
            std::fclose(f);
            return std::string();
        }
    }
    bool readError = std::ferror(f) != 0;
    std::fclose(f);
    if (readError) {
        EVP_MD_CTX_free(ctx);
        return std::string();
    }

    unsigned char digest[EVP_MAX_MD_SIZE];
    unsigned int digestLen = 0;
    if (EVP_DigestFinal_ex(ctx, digest, &digestLen) != 1) {
        EVP_MD_CTX_free(ctx);
        return std::string();
    }
    EVP_MD_CTX_free(ctx);

    static const char* hexDigits = "0123456789abcdef";
    std::string hex;
    hex.reserve(digestLen * 2);
    for (unsigned int i = 0; i < digestLen; ++i) {
        hex += hexDigits[digest[i] >> 4];
        hex += hexDigits[digest[i] & 0x0f];
    }
    return hex;
}

bool buildAudioDownloadWarning(const AudioDownloadSnapshot& snapshot,
                               bool dynamicAudio,
                               const std::string& selectedFilename,
                               std::string& message) {
    if (dynamicAudio) {
        if (snapshot.allAvailable) return false;
        message =
            "You currently have 'Dynamic Audio' selected, but some audio "
            "files are still being downloaded. Some audio will not play until "
            "these files have finished downloading.";
        return true;
    }

    for (const auto& file : snapshot.files) {
        if (file.filename != selectedFilename) continue;
        if (file.available) return false;
        const std::string name =
            file.display_name.empty() ? file.filename : file.display_name;
        message = "You currently have '" + name +
                  "' selected, but it is still being downloaded. No audio "
                  "will play until this file has finished downloading.";
        return true;
    }

    // The selection is not part of the manifest (the manifest may not be known
    // yet), so the downloader cannot confirm whether it is still downloading.
    return false;
}

// ─── Lifecycle ──────────────────────────────────────────────────────────

AudioDownloader::~AudioDownloader() {
    shutdown();
}

void AudioDownloader::start(db::DatabaseManager& db) {
    std::lock_guard<std::mutex> lock(mutex_);
    if (worker_.joinable()) return;
    db_ = &db;
    stop_ = false;
    worker_ = std::thread(&AudioDownloader::run, this);
}

void AudioDownloader::shutdown() {
    {
        std::lock_guard<std::mutex> lock(mutex_);
        stop_ = true;
    }
    cv_.notify_all();
    if (worker_.joinable()) worker_.join();
}

std::string AudioDownloader::statusString() const {
    std::lock_guard<std::mutex> lock(mutex_);
    return status_;
}

AudioDownloadSnapshot AudioDownloader::snapshot() const {
    std::lock_guard<std::mutex> lock(mutex_);
    return snapshot_;
}

void AudioDownloader::publishSnapshot(
    const std::vector<AudioManifestEntry>& manifest,
    const std::unordered_set<std::string>& availableFilenames) {
    AudioDownloadSnapshot snap;
    snap.manifestKnown = true;
    snap.allAvailable = !manifest.empty();
    snap.files.reserve(manifest.size());
    for (const auto& entry : manifest) {
        const bool available = availableFilenames.count(entry.filename) != 0;
        const std::string displayName =
            entry.display_name.empty() ? humanizeFilename(entry.filename)
                                       : entry.display_name;
        snap.files.push_back({entry.filename, displayName, available});
        if (!available) snap.allAvailable = false;
    }
    std::lock_guard<std::mutex> lock(mutex_);
    snapshot_ = std::move(snap);
}

void AudioDownloader::setStatus(const std::string& msg) {
    {
        std::lock_guard<std::mutex> lock(mutex_);
        status_ = msg;
    }
    cv_.notify_all();
}

void AudioDownloader::wait(std::chrono::seconds seconds) {
    std::unique_lock<std::mutex> lock(mutex_);
    cv_.wait_for(lock, seconds, [this]() { return stop_.load(); });
}

// ─── Worker loop ────────────────────────────────────────────────────────

void AudioDownloader::run() {
    logger::Logger::instance().info("Audio", "Audio downloader started");
    setStatus("Checking for audio updates...");

    while (!stop_.load()) {
        std::vector<AudioManifestEntry> manifest;
        if (!fetchManifest(manifest)) {
            setStatus("Waiting for internet...");
            wait(std::chrono::seconds(5));
            continue;
        }

        std::string dir = audioDir();
        std::unordered_map<std::string, int> orderByFilename;
        for (size_t i = 0; i < manifest.size(); ++i) {
            orderByFilename[manifest[i].filename] = static_cast<int>(i + 1);
        }

        // `available` is the set of files actually present on disk: files
        // whose checksum matches, plus files present but stale (they stay
        // listed while being re-downloaded). Files that don't exist yet are
        // excluded so the settings list reflects live download progress.
        std::vector<AudioManifestEntry> queue;
        std::vector<db::AudioFileRecord> available;
        std::unordered_set<std::string> listed;
        available.reserve(manifest.size());

        auto addAvailable = [&](const AudioManifestEntry& entry) {
            if (!listed.insert(entry.filename).second) return;
            available.push_back({0, entry.display_name, entry.filename,
                                 orderByFilename[entry.filename],
                                 frequencyIdForHz(entry.solfeggio_frequency_hz)});
        };
        // Publishes the current on-disk set to the database so the audio
        // settings list updates while the user is viewing it.
        auto syncNow = [&]() {
            if (db_ && !available.empty()) db_->syncAudioFiles(available);
        };

        for (const auto& entry : manifest) {
            std::string localMd5 = computeFileMd5(dir + entry.filename);
            if (localMd5 == entry.md5) {
                addAvailable(entry);
            } else if (!localMd5.empty()) {
                logger::Logger::instance().warning(
                    "Audio", "Checksum mismatch for " + entry.filename + ", re-downloading");
                addAvailable(entry);
                queue.push_back(entry);
            } else {
                queue.push_back(entry);
            }
        }

        size_t toDownload = queue.size();
        size_t downloaded = 0;

        // Publish what is (and is not) on disk before downloads begin so the
        // UI can warn immediately, then again as each file lands.
        publishSnapshot(manifest, listed);

        if (!queue.empty()) {
            std::error_code ec;
            std::filesystem::create_directories(dir, ec);

            for (const auto& work : queue) {
                if (stop_.load()) break;
                setStatus("Downloading audio files (" + std::to_string(downloaded + 1) +
                          " / " + std::to_string(queue.size()) + ")...");
                if (!downloadAndVerify(work.filename, work.md5, work.display_name)) break;
                addAvailable(work);
                ++downloaded;
                // Publish immediately so a file that just finished downloading
                // appears in the list without waiting for the rest.
                syncNow();
                publishSnapshot(manifest, listed);
            }
        }

        // Remove leftover audio files that are no longer in the manifest.
        std::error_code ec;
        if (std::filesystem::exists(dir)) {
            for (auto it = std::filesystem::directory_iterator(dir, ec), end = std::filesystem::directory_iterator();
                 !ec && it != end; it.increment(ec)) {
                if (!it->is_regular_file(ec)) continue;
                std::string name = it->path().filename().string();
                if (name.empty() || name.front() == '.' ||
                    name.size() >= 5 && name.compare(name.size() - 5, 5, ".part") == 0) {
                    continue;
                }
                if (orderByFilename.count(name) == 0) {
                    logger::Logger::instance().debug("Audio", "Removing leftover " + name);
                    std::filesystem::remove(it->path(), ec);
                }
            }
        }

        // Final reconcile so rows for files removed from disk are dropped too.
        // Runs even when nothing is available, so an empty on-disk set clears
        // any stale rows.
        if (db_) db_->syncAudioFiles(available);

        bool upToDate = downloaded == toDownload;
        if (upToDate && !stop_.load()) {
            setStatus("Audio files up to date");
            wait(std::chrono::seconds(60));
        } else {
            wait(std::chrono::seconds(5));
        }
    }

    logger::Logger::instance().info("Audio", "Audio downloader stopped");
}

bool AudioDownloader::fetchManifest(std::vector<AudioManifestEntry>& out) {
    std::string body;
    std::string url = std::string(AUDIO_BASE_URL) + MANIFEST_FILENAME;
    if (!httpGetString(url, body)) {
        logger::Logger::instance().debug("Audio", "Failed to fetch audio manifest");
        return false;
    }
    if (!parseManifest(body, out)) {
        logger::Logger::instance().warning("Audio", "Audio manifest was unparseable");
        return false;
    }
    return true;
}

bool AudioDownloader::downloadAndVerify(const std::string& filename, const std::string& expectedMd5, const std::string& displayName) {
    std::string dir = audioDir();
    std::string destPath = dir + filename;
    std::string tmpPath = destPath + ".part";

    std::error_code ec;
    std::filesystem::remove(tmpPath, ec);

    if (!httpGetFile(std::string(AUDIO_BASE_URL) + filename, tmpPath)) {
        logger::Logger::instance().warning("Audio", "Download failed for " + filename);
        std::filesystem::remove(tmpPath, ec);
        return false;
    }

    std::string gotMd5 = computeFileMd5(tmpPath);
    if (gotMd5 != expectedMd5) {
        logger::Logger::instance().warning(
            "Audio", "Checksum mismatch after download for " + filename);
        std::filesystem::remove(tmpPath, ec);
        return false;
    }

    std::filesystem::rename(tmpPath, destPath, ec);
    if (ec) {
        logger::Logger::instance().warning("Audio", "Could not move " + filename + " into place");
        std::filesystem::remove(tmpPath, ec);
        return false;
    }

    logger::Logger::instance().info("Audio", "Downloaded and verified " + displayName);
    return true;
}

} // namespace radiantwave::audio