const fs = require("fs/promises");
const path = require("path");

async function collectMarkdownFiles(rootDir, { skipIndex = true } = {}) {
    const entries = await fs.readdir(rootDir, { withFileTypes: true });
    const files = [];

    for (const entry of entries) {
        const fullPath = path.join(rootDir, entry.name);

        if (entry.isDirectory()) {
            const nested = await collectMarkdownFiles(fullPath, { skipIndex });
            files.push(...nested);
            continue;
        }

        if (!entry.isFile()) continue;
        if (!entry.name.toLowerCase().endsWith(".md")) continue;
        if (skipIndex && entry.name === "_index.md") continue;

        files.push(fullPath);
    }

    return files;
}

async function collectSectionIndexDirs(rootDir) {
    const sections = new Set();

    async function walk(dir) {
        let entries;
        try {
            entries = await fs.readdir(dir, { withFileTypes: true });
        } catch (error) {
            console.error(`Skipping section scan for ${dir}: ${error.message}`);
            return;
        }

        let hasIndex = false;
        for (const entry of entries) {
            if (entry.isFile() && entry.name.toLowerCase() === "_index.md") {
                hasIndex = true;
                break;
            }
        }

        if (hasIndex) {
            sections.add(path.resolve(dir));
        }

        for (const entry of entries) {
            if (entry.isDirectory()) {
                await walk(path.join(dir, entry.name));
            }
        }
    }

    await walk(rootDir);
    return sections;
}

async function resolveMarkdownTargets(inputs, { rootDir = process.cwd(), skipIndex = true } = {}) {
    if (!inputs || inputs.length === 0) {
        return collectMarkdownFiles(rootDir, { skipIndex });
    }

    const targets = new Set();

    for (const input of inputs) {
        const resolved = path.resolve(input);

        try {
            const stat = await fs.stat(resolved);

            if (stat.isDirectory()) {
                const nested = await collectMarkdownFiles(resolved, { skipIndex });
                nested.forEach((file) => targets.add(file));
                continue;
            }

            if (stat.isFile()) {
                const lower = resolved.toLowerCase();
                if (!lower.endsWith(".md")) continue;
                if (skipIndex && path.basename(resolved) === "_index.md") continue;
                targets.add(resolved);
            }
        } catch (error) {
            console.error(`Skipping ${input}: ${error.message}`);
        }
    }

    return Array.from(targets);
}

module.exports = {
    collectMarkdownFiles,
    collectSectionIndexDirs,
    resolveMarkdownTargets,
};