const crypto = require("crypto");
const fs = require("fs");
const path = require("path");

function isPlainObject(value) {
    return value !== null && typeof value === "object" && !Array.isArray(value);
}

function overlaySettingsValue(base, overlay) {
    if (!isPlainObject(base) || !isPlainObject(overlay)) return overlay;

    const result = { ...base };
    for (const [key, value] of Object.entries(overlay)) {
        result[key] = key in result ? overlaySettingsValue(result[key], value) : value;
    }
    return result;
}

function applySettingOverlay(settings, projectRoot, overlayPath) {
    const resolvedPath = path.isAbsolute(overlayPath) ? overlayPath : path.resolve(projectRoot, overlayPath);
    const overlay = JSON.parse(fs.readFileSync(resolvedPath, "utf8"));
    if (!isPlainObject(overlay)) throw new Error(`Setting overlay must contain an object: ${overlayPath}`);

    for (const [name, value] of Object.entries(overlay)) {
        settings.set(name, settings.has(name) ? overlaySettingsValue(settings.get(name), value) : value);
    }
}

function loadSettings(projectRoot, settingOverlays = []) {
    const settingsRoot = path.join(projectRoot, "settings");
    if (!fs.existsSync(settingsRoot)) throw new Error(`No settings folder found in ${projectRoot}`);

    const settings = new Map();
    for (const fileName of fs.readdirSync(settingsRoot)) {
        if (path.extname(fileName).toLowerCase() !== ".json") continue;
        const name = path.basename(fileName, path.extname(fileName));
        const filePath = path.join(settingsRoot, fileName);
        settings.set(name, JSON.parse(fs.readFileSync(filePath, "utf8")));
    }
    for (const overlayPath of settingOverlays) applySettingOverlay(settings, projectRoot, overlayPath);
    return settings;
}

function hashPayload(value) {
    const json = JSON.stringify(value);
    return crypto.createHash("sha256").update(json === undefined ? "undefined" : json).digest("hex");
}

function getSourceHash(sources) {
    const sourceHash = {};
    for (const [name, source] of Object.entries(sources)) {
        if (!source || typeof source !== "object" || !("hash" in source)) {
            throw new Error(`Source "${name}" must be a node with a hash`);
        }
        sourceHash[name] = source.hash;
    }
    return sourceHash;
}

function buildNode(payload, sources = {}) {
    return {
        sourceHash: getSourceHash(sources),
        hash: hashPayload(payload),
        payload,
    };
}

function buildBinaryNode(filePath, sources = {}) {
    const bytes = fs.readFileSync(filePath);
    return {
        sourceHash: getSourceHash(sources),
        hash: crypto.createHash("sha256").update(bytes).digest("hex"),
        payloadBin: filePath,
    };
}

function initialize(projectRoot = process.cwd(), options = {}) {
    const settingOverlays = options.settingOverlays || [];
    if (!Array.isArray(settingOverlays)) throw new Error("options.settingOverlays must be an array");
    const settings = loadSettings(projectRoot, settingOverlays);
    const registry = new Map();
    let artifactOutcome;

    const utils = {
        loadModule(name) {
            const entry = registry.get(name);
            if (!entry) throw new Error(`Unknown module: ${name}`);
            if (entry.module) return entry.module;
            if (entry.initializing) throw new Error(`Circular module initialization involving: ${name}`);

            entry.initializing = true;
            try {
                const initialized = entry.init(utils);
                if (!initialized || (typeof initialized !== "object" && typeof initialized !== "function")) {
                    throw new Error(`Module "${name}" initializer must return a module object or function`);
                }
                entry.module = initialized;
                return entry.module;
            } finally {
                entry.initializing = false;
            }
        },

        getSettings(name) {
            if (!settings.has(name)) throw new Error(`Unknown settings: ${name}`);
            return settings.get(name);
        },

        hashPayload,
        buildNode,
        buildBinaryNode,

        setArtifactOutcome(value) {
            artifactOutcome = `${value ?? ""}`.trim() || undefined;
        },
    };

    const modules = utils.getSettings("modules");
    if (!modules || typeof modules !== "object" || Array.isArray(modules)) throw new Error("settings/modules.json must contain an object");

    for (const [name, modulePath] of Object.entries(modules)) {
        const resolvedPath = path.resolve(projectRoot, modulePath);
        const init = require(resolvedPath);
        if (typeof init !== "function") throw new Error(`Module "${name}" must export an initializer function: ${modulePath}`);
        registry.set(name, { init, module: null, initializing: false });
    }

    for (const name of registry.keys()) utils.loadModule(name);

    function buildArtifact(name) {
        const artifacts = utils.getSettings("artifacts");
        const artifact = artifacts[name];
        if (!artifact) throw new Error(`Unknown artifact: ${name}`);
        if (!artifact.module) throw new Error(`Artifact "${name}" is missing module`);
        if (!artifact.builder) throw new Error(`Artifact "${name}" is missing builder`);

        const module = utils.loadModule(artifact.module);
        const builder = module[artifact.builder];
        if (typeof builder !== "function") {
            throw new Error(`Artifact "${name}" builder not found: ${artifact.module}.${artifact.builder}`);
        }

        const params = artifact.params === undefined ? [] : artifact.params;
        if (!Array.isArray(params)) throw new Error(`Artifact "${name}" params must be an array`);

        artifactOutcome = undefined;
        console.log(`Ensuring artifact: ${name}`);
        try {
            const result = builder(...params);
            if (result && typeof result.then === "function") {
                return result.then(value => {
                    console.log(`  ${artifactOutcome ?? "completed — success"}`);
                    artifactOutcome = undefined;
                    return value;
                }, error => {
                    console.error("  failed");
                    artifactOutcome = undefined;
                    throw error;
                });
            }

            console.log(`  ${artifactOutcome ?? "completed — success"}`);
            artifactOutcome = undefined;
            return result;
        }
        catch (error) {
            console.error("  failed");
            artifactOutcome = undefined;
            throw error;
        }
    }

    async function buildAll() {
        const artifacts = utils.getSettings("artifacts");
        for (const name of Object.keys(artifacts)) await buildArtifact(name);
    }

    return {
        utils,
        loadModule: utils.loadModule,
        getSettings: utils.getSettings,
        hashPayload,
        buildNode,
        buildBinaryNode,
        buildArtifact,
        buildAll,
        modules: [...registry.keys()],
    };
}

module.exports = { initialize, hashPayload, buildNode, buildBinaryNode };