import sharp from 'sharp';
import fs from 'fs';
import path from 'path';
import crypto from 'crypto';
import { fileURLToPath } from 'url';

const __dirname = path.dirname(fileURLToPath(import.meta.url));
const ROOT = path.join(__dirname, '..');
const IMAGE_CACHE_ROOT = process.env.IMAGE_CACHE_ROOT?.trim();
const CACHE_ROOT = IMAGE_CACHE_ROOT
  ? path.resolve(IMAGE_CACHE_ROOT, 'manifests')
  : path.join(ROOT, '.cache', 'image-manifests');
const CACHED_ORIGINALS_ROOT = IMAGE_CACHE_ROOT
  ? path.resolve(IMAGE_CACHE_ROOT, 'originals')
  : null;
const CACHED_OUTPUTS_ROOT = IMAGE_CACHE_ROOT
  ? path.resolve(IMAGE_CACHE_ROOT, 'optimized')
  : null;
const IMAGE_PIPELINE_VERSION = 1;
const PUBLIC_IMAGES_ROOT = path.join(ROOT, 'public/images');
const DEFAULT_MEDIA_ROOT = path.join(ROOT, '.media-source');
const LEGACY_MEDIA_ROOT = path.join(ROOT, 'assets');

// Optional project-specific alt texts keyed by source image name.
const altTexts = {};

const quality = { jpeg: 85, webp: 80, avif: 50, png: 9 };
const supportedExts = new Set(['.jpg', '.jpeg', '.png']);
const SHOULD_PRUNE = process.argv.includes('--prune');
const REQUIRE_IMAGE_SOURCES = process.env.IMAGES_SOURCE_REQUIRED === 'true';

function resolveSourceDir(relativePath) {
  const envRoot = process.env.MEDIA_SOURCE_ROOT?.trim();
  const candidates = [
    envRoot ? path.resolve(ROOT, envRoot, relativePath) : null,
    path.join(DEFAULT_MEDIA_ROOT, relativePath),
    path.join(LEGACY_MEDIA_ROOT, relativePath),
  ].filter(Boolean);

  for (const candidate of candidates) {
    if (fs.existsSync(candidate)) {
      return candidate;
    }
  }

  return path.join(DEFAULT_MEDIA_ROOT, relativePath);
}

/**
 * Pipeline-Konfigurationen
 */
const pipelines = [
  {
    name: 'content',
    sourceDir: resolveSourceDir('original-content'),
    outputDir: path.join(PUBLIC_IMAGES_ROOT, 'content'),
    outputRelativeDir: 'content',
    recursive: true,
    sizes: [
      { suffix: '-sm', width: 800, height: 600 },
      { suffix: '-md', width: 1000, height: 750 },
    ],
    formats: ['original', 'webp', 'avif'],
    deleteOriginal: false,
    generateJson: false,
  },
  {
    name: 'slider',
    sourceDir: resolveSourceDir('original-slider'),
    outputDir: path.join(PUBLIC_IMAGES_ROOT, 'slider'),
    outputRelativeDir: 'slider',
    recursive: false,
    sizes: [
      { suffix: '-sm', width: 640, height: 480 },
      { suffix: '-md', width: 1280, height: 960 },
      { suffix: '', width: 1920, height: 1440 },
    ],
    formats: ['jpg', 'webp', 'avif'],
    deleteOriginal: false,
    generateJson: true,
    jsonFileName: 'slider-images.json',
  },
  {
    name: 'secondary-slider',
    sourceDir: resolveSourceDir('original-secondary-slider'),
    outputDir: path.join(PUBLIC_IMAGES_ROOT, 'secondary-slider'),
    outputRelativeDir: 'secondary-slider',
    recursive: false,
    sizes: [
      { suffix: '-sm', width: 640, height: 480 },
      { suffix: '-md', width: 1280, height: 960 },
      { suffix: '', width: 1920, height: 1440 },
    ],
    formats: ['jpg', 'webp', 'avif'],
    deleteOriginal: false,
    generateJson: true,
    jsonFileName: 'slider-images.json',
  },
  {
    name: 'herosections',
    sourceDir: resolveSourceDir('original-herosections'),
    outputDir: path.join(PUBLIC_IMAGES_ROOT, 'backgrounds'),
    outputRelativeDir: 'backgrounds',
    recursive: false,
    sizes: [
      { suffix: '', width: 1920, height: 1440 },
      { suffix: '-mobile', width: 1024, height: 768 },
    ],
    formats: ['jpg', 'webp', 'avif'],
    deleteOriginal: false,
    generateJson: false,
  },
];

function isVariantFile(fileName, sizeSuffixes) {
  const ext = path.extname(fileName).toLowerCase();
  const base = path.basename(fileName, path.extname(fileName)).toLowerCase();
  if (ext === '.webp' || ext === '.avif') return true;
  if (base.endsWith('-temp')) return true;
  return sizeSuffixes.some((s) => s && base.endsWith(s));
}

function collectImages(dirPath, recursive, sizeSuffixes) {
  const collected = [];
  const entries = fs.readdirSync(dirPath, { withFileTypes: true });
  for (const entry of entries) {
    const fullPath = path.join(dirPath, entry.name);
    if (entry.isDirectory() && recursive) {
      collected.push(...collectImages(fullPath, true, sizeSuffixes));
      continue;
    }
    if (!entry.isFile()) continue;
    const ext = path.extname(entry.name).toLowerCase();
    if (!supportedExts.has(ext)) continue;
    if (isVariantFile(entry.name, sizeSuffixes)) continue;
    collected.push(fullPath);
  }
  return collected;
}

function collectBaseImageRecords(dirPath, recursive, sizeSuffixes) {
  if (!fs.existsSync(dirPath)) return [];
  return collectImages(dirPath, recursive, sizeSuffixes)
    .map((filePath) => ({
      name: path.basename(filePath, path.extname(filePath)),
      ext: path.extname(filePath),
      relDir: path.relative(dirPath, path.dirname(filePath)),
    }))
    .sort((a, b) => a.name.localeCompare(b.name));
}

function collectOutputFileNames(dirPath) {
  if (!fs.existsSync(dirPath)) return [];
  return fs.readdirSync(dirPath, { withFileTypes: true })
    .filter((entry) => entry.isFile())
    .map((entry) => entry.name);
}

function readJsonManifest(manifestPath) {
  try {
    if (!fs.existsSync(manifestPath)) return [];
    const parsed = JSON.parse(fs.readFileSync(manifestPath, 'utf8'));
    return Array.isArray(parsed) ? parsed : [];
  } catch {
    return [];
  }
}

function getBaseOutputRecords(outputFileNames, sizeSuffixes) {
  return outputFileNames
    .filter((fileName) => {
      const ext = path.extname(fileName).toLowerCase();
      return supportedExts.has(ext) && !isVariantFile(fileName, sizeSuffixes);
    })
    .map((fileName) => ({
      name: path.basename(fileName, path.extname(fileName)),
      ext: path.extname(fileName),
    }))
    .sort((a, b) => a.name.localeCompare(b.name));
}

function manifestKeyForRecord(record) {
  return record.relDir ? `${record.relDir}/${record.name}` : record.name;
}

function stripGeneratedSuffix(baseName, sizeSuffixes) {
  const sortedSuffixes = [...sizeSuffixes]
    .filter(Boolean)
    .sort((a, b) => b.length - a.length);
  for (const suffix of sortedSuffixes) {
    if (baseName.endsWith(suffix)) {
      return baseName.slice(0, -suffix.length);
    }
  }
  return baseName;
}

function collectGeneratedOutputFiles(dirPath, rootDir = dirPath) {
  if (!fs.existsSync(dirPath)) return [];
  const files = [];
  for (const entry of fs.readdirSync(dirPath, { withFileTypes: true })) {
    const fullPath = path.join(dirPath, entry.name);
    if (entry.isDirectory()) {
      files.push(...collectGeneratedOutputFiles(fullPath, rootDir));
      continue;
    }
    if (!entry.isFile()) continue;
    const ext = path.extname(entry.name).toLowerCase();
    if (!new Set([...supportedExts, '.webp', '.avif']).has(ext)) continue;
    files.push({
      path: fullPath,
      fileName: entry.name,
      relDir: path.relative(rootDir, path.dirname(fullPath)),
    });
  }
  return files;
}

function removeEmptyDirs(dirPath, rootDir) {
  if (!fs.existsSync(dirPath) || dirPath === rootDir) return;
  if (fs.readdirSync(dirPath).length > 0) return;
  fs.rmdirSync(dirPath);
  removeEmptyDirs(path.dirname(dirPath), rootDir);
}

function pruneGeneratedAssets(config, sourceRecords, sizeSuffixes) {
  const sourceKeys = new Set(sourceRecords.map(manifestKeyForRecord));
  let removed = 0;
  for (const outputFile of collectGeneratedOutputFiles(config.outputDir)) {
    const baseName = stripGeneratedSuffix(
      path.basename(outputFile.fileName, path.extname(outputFile.fileName)),
      sizeSuffixes,
    );
    const key = outputFile.relDir ? `${outputFile.relDir}/${baseName}` : baseName;
    if (sourceKeys.has(key)) continue;
    fs.rmSync(outputFile.path);
    removeEmptyDirs(path.dirname(outputFile.path), config.outputDir);
    removed++;
  }
  if (removed > 0) {
    console.log(`[${config.name}] ${removed} verwaiste Bilddatei(en) entfernt`);
  }
}

export function buildImageManifestEntries({
  existingManifest = [],
  outputFileNames = [],
  sourceRecords = [],
  sizeSuffixes = [],
  altTextsByName = altTexts,
  sourceIsComplete = false,
} = {}) {
  const outputRecords = getBaseOutputRecords(outputFileNames, sizeSuffixes);
  const outputNames = new Set(outputRecords.map(manifestKeyForRecord));
  const sourceNames = new Set(sourceRecords.map(manifestKeyForRecord));
  const sourceByName = new Map(sourceRecords.map((record) => [manifestKeyForRecord(record), record]));
  const outputByName = new Map(outputRecords.map((record) => [manifestKeyForRecord(record), record]));
  const webpNames = new Set(outputFileNames
    .filter((fileName) => path.extname(fileName).toLowerCase() === '.webp')
    .map((fileName) => path.basename(fileName, path.extname(fileName)).replace(/-(sm|md|mobile)$/i, '')));
  const avifNames = new Set(outputFileNames
    .filter((fileName) => path.extname(fileName).toLowerCase() === '.avif')
    .map((fileName) => path.basename(fileName, path.extname(fileName)).replace(/-(sm|md|mobile)$/i, '')));

  const entries = new Map();
  const addEntry = (record, existing = {}) => {
    if (!record?.name || !record?.ext) return;
    const key = manifestKeyForRecord(record);
    entries.set(key, {
      name: record.name,
      ext: record.ext,
      alt: existing.alt ?? altTextsByName[record.name],
      webp: webpNames.has(record.name),
      avif: avifNames.has(record.name),
    });
  };

  for (const item of existingManifest) {
    if (!item?.name) continue;
    const key = manifestKeyForRecord(item);
    if (sourceIsComplete && !sourceNames.has(key)) continue;
    if (!sourceIsComplete && !outputNames.has(key) && !sourceNames.has(key)) continue;
    const record = sourceByName.get(key) ?? outputByName.get(key) ?? item;
    addEntry(record, item);
  }

  const defaultRecords = sourceIsComplete || existingManifest.length > 0 ? sourceRecords : outputRecords;
  for (const record of defaultRecords) {
    if (!entries.has(manifestKeyForRecord(record))) {
      addEntry(record);
    }
  }

  return [...entries.values()]
    .filter((entry) => entry.name && entry.ext)
    .sort((a, b) => a.name.localeCompare(b.name));
}

async function collectOutputMetadata(outputDir, outputFileNames) {
  const metadata = new Map();

  await Promise.all(outputFileNames.map(async (fileName) => {
    const ext = path.extname(fileName).toLowerCase();
    if (![...supportedExts, '.webp', '.avif'].includes(ext)) return;

    const dimensions = await sharp(path.join(outputDir, fileName)).metadata();
    if (!dimensions.width || !dimensions.height) return;
    metadata.set(fileName, {
      width: dimensions.width,
      height: dimensions.height,
    });
  }));

  return metadata;
}

export function addImageManifestMetadata({
  entries = [],
  outputMetadata = new Map(),
  sizes = [],
  fallbackExtension = '.jpg',
} = {}) {
  return entries.flatMap((entry) => {
    const variantsForExtension = (extension) => sizes.flatMap(({ suffix }) => {
      const file = `${entry.name}${suffix}${extension}`;
      const dimensions = outputMetadata.get(file);
      return dimensions ? [{ file, ...dimensions }] : [];
    });
    const fallback = variantsForExtension(fallbackExtension);
    const base = fallback.find((variant) => variant.file === `${entry.name}${fallbackExtension}`)
      ?? fallback.at(-1);

    if (!base) return [];

    return [{
      ...entry,
      width: base.width,
      height: base.height,
      variants: {
        fallback,
        webp: variantsForExtension('.webp'),
        avif: variantsForExtension('.avif'),
      },
    }];
  });
}

async function writeImageManifest(config, outDir, sourceRecords, sizeSuffixes, sourceIsComplete) {
  const jsonName = config.jsonFileName || 'images.json';
  const jsonPath = path.join(outDir, jsonName);
  const outputFileNames = collectOutputFileNames(outDir);
  const entries = buildImageManifestEntries({
    existingManifest: readJsonManifest(jsonPath),
    outputFileNames,
    sourceRecords,
    sizeSuffixes,
    sourceIsComplete,
  });
  const fallbackExtension = config.formats.includes('original')
    ? entries[0]?.ext
    : '.jpg';
  const outputMetadata = await collectOutputMetadata(outDir, outputFileNames);
  const imagesList = addImageManifestMetadata({
    entries,
    outputMetadata,
    sizes: config.sizes,
    fallbackExtension,
  });
  fs.writeFileSync(jsonPath, JSON.stringify(imagesList, null, 2));
}

function fileHash(filePath) {
  return crypto.createHash('md5').update(fs.readFileSync(filePath)).digest('hex');
}

function getEncoder(extLower) {
  if (extLower === '.png') {
    return (pipeline) => pipeline.png({ compressionLevel: quality.png, adaptiveFiltering: true });
  }
  return (pipeline) => pipeline.jpeg({ quality: quality.jpeg, progressive: true, mozjpeg: true });
}

function getFormatPriority(format) {
  if (format === 'original' || format === 'jpg') return 0;
  if (format === 'webp') return 1;
  if (format === 'avif') return 2;
  return 3;
}

function replaceFile(fromPath, toPath) {
  if (fs.existsSync(toPath)) {
    fs.rmSync(toPath);
  }
  fs.renameSync(fromPath, toPath);
}

function copyFileWithParents(sourcePath, destinationPath) {
  fs.mkdirSync(path.dirname(destinationPath), { recursive: true });
  fs.copyFileSync(sourcePath, destinationPath);
}

function pruneCachedOriginals(config, sourceRecords) {
  if (!CACHED_ORIGINALS_ROOT) return;
  const cachedDir = path.join(CACHED_ORIGINALS_ROOT, config.name);
  const sourceKeys = new Set(sourceRecords.map(manifestKeyForRecord));
  for (const cachedFile of collectGeneratedOutputFiles(cachedDir)) {
    const baseName = path.basename(cachedFile.fileName, path.extname(cachedFile.fileName));
    const key = cachedFile.relDir ? `${cachedFile.relDir}/${baseName}` : baseName;
    if (sourceKeys.has(key)) continue;
    fs.rmSync(cachedFile.path);
    removeEmptyDirs(path.dirname(cachedFile.path), cachedDir);
  }
}

function mirrorCachedOutput(config, outDir) {
  if (!CACHED_OUTPUTS_ROOT) return;

  // These directories contain only generated variants. Replacing them makes a
  // removed Git source disappear from the image that is being built as well.
  fs.rmSync(config.outputDir, { recursive: true, force: true });
  fs.mkdirSync(path.dirname(config.outputDir), { recursive: true });
  fs.cpSync(outDir, config.outputDir, { recursive: true });
}

function hasFallbackVariants(config, fileOutDir, baseName, ext) {
  const fallbackFormat = config.formats.includes('original') ? 'original' : 'jpg';
  const fallbackExt = fallbackFormat === 'original' ? ext : '.jpg';
  return config.sizes.every((size) =>
    fs.existsSync(path.join(fileOutDir, `${baseName}${size.suffix}${fallbackExt}`))
  );
}

async function runPipeline(config) {
  if (!fs.existsSync(config.sourceDir)) {
    const outDir = config.outputDir ?? config.sourceDir;
    const hasGeneratedAssets = fs.existsSync(outDir);
    if (REQUIRE_IMAGE_SOURCES || !hasGeneratedAssets) {
      throw new Error(`[${config.name}] Quellverzeichnis fehlt: ${config.sourceDir}`);
    }
    console.warn(
      `[${config.name}] Quellverzeichnis fehlt (${config.sourceDir}). ` +
      `Verwende vorhandene optimierte Assets in ${outDir}.`
    );
    return;
  }

  const outDir = CACHED_OUTPUTS_ROOT
    ? path.join(CACHED_OUTPUTS_ROOT, config.outputRelativeDir)
    : (config.outputDir ?? config.sourceDir);
  if (!fs.existsSync(outDir)) {
    fs.mkdirSync(outDir, { recursive: true });
  }

  if (!fs.existsSync(CACHE_ROOT)) {
    fs.mkdirSync(CACHE_ROOT, { recursive: true });
  }

  // Manifest for hash caching outside the public asset tree
  const manifestPath = path.join(CACHE_ROOT, `${config.name}.json`);
  let manifest = {};
  try {
    if (fs.existsSync(manifestPath)) {
      manifest = JSON.parse(fs.readFileSync(manifestPath, 'utf8'));
    }
  } catch { manifest = {}; }

  const sizeSuffixes = config.sizes.map((s) => s.suffix);
  const files = collectImages(config.sourceDir, config.recursive, sizeSuffixes);
  const sourceRecords = collectBaseImageRecords(config.sourceDir, config.recursive, sizeSuffixes);
  const sourceIsComplete = fs.existsSync(config.sourceDir);
  const outputConfig = { ...config, outputDir: outDir };
  let manifestChanged = false;

  if (SHOULD_PRUNE && sourceIsComplete) {
    pruneGeneratedAssets(outputConfig, sourceRecords, sizeSuffixes);
    pruneCachedOriginals(config, sourceRecords);
    for (const key of Object.keys(manifest)) {
      if (!sourceRecords.some((record) => manifestKeyForRecord(record) === key)) {
        delete manifest[key];
        manifestChanged = true;
      }
    }
  }

  if (files.length === 0) {
    console.log(`[${config.name}] Keine Bilder gefunden.`);
    if (config.generateJson) {
      await writeImageManifest(config, outDir, sourceRecords, sizeSuffixes, sourceIsComplete);
    }
    if (manifestChanged) {
      fs.writeFileSync(manifestPath, JSON.stringify(manifest, null, 2));
    }
    mirrorCachedOutput(config, outDir);
    return;
  }

  console.log(`[${config.name}] ${files.length} Bilder gefunden`);
  let processed = 0;

  for (const inputPath of files) {
    const file = path.basename(inputPath);
    const ext = path.extname(file);
    const extLower = ext.toLowerCase();
    const baseName = path.basename(file, ext);
    const relDir = path.relative(config.sourceDir, path.dirname(inputPath));
    const fileOutDir = relDir ? path.join(outDir, relDir) : outDir;

    const hash = fileHash(inputPath);
    const manifestKey = relDir ? `${relDir}/${baseName}` : baseName;

    if (CACHED_ORIGINALS_ROOT) {
      const cachedOriginalPath = path.join(CACHED_ORIGINALS_ROOT, config.name, relDir, file);
      if (manifest[manifestKey]?.hash !== hash || !fs.existsSync(cachedOriginalPath)) {
        copyFileWithParents(inputPath, cachedOriginalPath);
      }
    }

    if (
      manifest[manifestKey]?.hash === hash &&
      manifest[manifestKey]?.optimized &&
      manifest[manifestKey]?.version === IMAGE_PIPELINE_VERSION &&
      hasFallbackVariants(config, fileOutDir, baseName, ext)
    ) {
      continue;
    }

    if (!fs.existsSync(fileOutDir)) {
      fs.mkdirSync(fileOutDir, { recursive: true });
    }

    let totalVariantSize = 0;
    const originalSize = fs.statSync(inputPath).size;
    const orderedFormats = [...config.formats].sort((left, right) => getFormatPriority(left) - getFormatPriority(right));

    for (const size of config.sizes) {
      const resizeOpts = { width: size.width, height: size.height, fit: 'inside', withoutEnlargement: true };
      let fallbackVariantSize = Number.POSITIVE_INFINITY;

      for (const format of orderedFormats) {
        let outputPath;
        let pipeline = sharp(inputPath).rotate().resize(resizeOpts);

        if (format === 'original') {
          outputPath = path.join(fileOutDir, `${baseName}${size.suffix}${ext}`);
          pipeline = getEncoder(extLower)(pipeline);
        } else if (format === 'jpg') {
          outputPath = path.join(fileOutDir, `${baseName}${size.suffix}.jpg`);
          pipeline = pipeline.jpeg({ quality: quality.jpeg, progressive: true, mozjpeg: true });
        } else if (format === 'webp') {
          outputPath = path.join(fileOutDir, `${baseName}${size.suffix}.webp`);
          pipeline = pipeline.webp({ quality: quality.webp });
        } else if (format === 'avif') {
          outputPath = path.join(fileOutDir, `${baseName}${size.suffix}.avif`);
          pipeline = pipeline.avif({ quality: quality.avif });
        }

        const tempPath = `${outputPath}.tmp`;
        if (fs.existsSync(tempPath)) {
          fs.rmSync(tempPath);
        }

        await pipeline.toFile(tempPath);

        const candidateSize = fs.statSync(tempPath).size;
        const existingSize = fs.existsSync(outputPath) ? fs.statSync(outputPath).size : null;
        const isDerivedVariant = format === 'webp' || format === 'avif';

        if (isDerivedVariant && Number.isFinite(fallbackVariantSize) && candidateSize >= fallbackVariantSize) {
          fs.rmSync(tempPath);
          if (existingSize !== null && existingSize < fallbackVariantSize) {
            totalVariantSize += existingSize;
          } else if (existingSize !== null && SHOULD_PRUNE) {
            fs.rmSync(outputPath);
          }
          continue;
        }

        if (existingSize !== null && existingSize <= candidateSize) {
          fs.rmSync(tempPath);
          totalVariantSize += existingSize;
          if (format === 'original' || format === 'jpg') {
            fallbackVariantSize = existingSize;
          }
          continue;
        }

        replaceFile(tempPath, outputPath);
        totalVariantSize += candidateSize;

        if (format === 'original' || format === 'jpg') {
          fallbackVariantSize = candidateSize;
        }
      }
    }

    manifest[manifestKey] = {
      hash,
      optimized: true,
      originalSize,
      version: IMAGE_PIPELINE_VERSION,
      timestamp: new Date().toISOString(),
    };
    manifestChanged = true;

    if (config.deleteOriginal) {
      fs.rmSync(inputPath);
    }

    if (totalVariantSize < originalSize) {
      const saving = (((originalSize - totalVariantSize) / originalSize) * 100).toFixed(1);
      console.log(`  ${file} → ${saving}% Ersparnis`);
    } else {
      console.log(`  ${file} → Varianten aktualisiert`);
    }
    processed++;
  }

  // Generate JSON manifest if needed
  if (config.generateJson) {
    await writeImageManifest(config, outDir, sourceRecords, sizeSuffixes, sourceIsComplete);
  }

  if (manifestChanged) {
    fs.writeFileSync(manifestPath, JSON.stringify(manifest, null, 2));
  }

  mirrorCachedOutput(config, outDir);

  if (processed > 0) {
    console.log(`[${config.name}] ${processed} Bild(er) optimiert`);
  } else {
    console.log(`[${config.name}] Alle Bilder aktuell`);
  }
}

// Run all pipelines
if (path.resolve(process.argv[1] ?? '') === fileURLToPath(import.meta.url)) {
  for (const pipeline of pipelines) {
    await runPipeline(pipeline);
  }
}