import { Router, Request, Response } from 'express';
import fs from 'fs';
import path from 'path';
import https from 'https';

const FONTS_DIR = path.join( __dirname, '..', '..', '..', 'storage', 'fonts' );

const GOOGLE_FONTS_UA = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36';
const ALL_WEIGHTS     = [ 100, 200, 300, 400, 500, 600, 700, 800, 900 ];

// ─── types ───────────────────────────────────────────────────────────────────

interface FontMeta
{
  family: string;
  weights: string[];
  italics: string[];
}

// ─── helpers ─────────────────────────────────────────────────────────────────

function fontsDir( family: string ): string
{
  return path.join( FONTS_DIR, family.toLowerCase() );
}

function readMeta( family: string ): FontMeta | null
{
  const p = path.join( fontsDir( family ), 'meta.json' );
  if ( !fs.existsSync( p ) ) return null;
  return JSON.parse( fs.readFileSync( p, 'utf8' ) );
}

function writeMeta( meta: FontMeta ): void
{
  fs.writeFileSync(
    path.join( fontsDir( meta.family ), 'meta.json' ),
    JSON.stringify( meta, null, 2 )
  );
}

function fontFileExists( family: string, weight: string, italic: boolean ): boolean
{
  const name = italic ? `${weight}-italic.woff2` : `${weight}.woff2`;
  return fs.existsSync( path.join( fontsDir( family ), name ) );
}

function buildFontFace( displayFamily: string, weight: string, italic: boolean ): string
{
  const style    = italic ? 'italic' : 'normal';
  const fileName = italic ? `${weight}-italic.woff2` : `${weight}.woff2`;
  const url      = `/fonts/${displayFamily.toLowerCase()}/${fileName}`;
  return [
    '@font-face {',
    `  font-family: '${displayFamily}';`,
    `  font-style: ${style};`,
    `  font-weight: ${weight};`,
    `  src: url('${url}') format('woff2');`,
    '  font-display: swap;',
    '}',
  ].join( '\n' );
}

function httpsGet( url: string, headers: Record<string, string> = {} ): Promise<string>
{
  return new Promise( ( resolve, reject ) =>
  {
    const req = https.get( url, { headers }, res =>
    {
      if ( res.statusCode >= 300 && res.statusCode < 400 && res.headers.location )
      {
        resolve( httpsGet( res.headers.location, headers ) );
        return;
      }
      let data = '';
      res.on( 'data', chunk => { data += chunk; } );
      res.on( 'end', () => resolve( data ) );
    } );
    req.on( 'error', reject );
  } );
}

function httpsGetBuffer( url: string ): Promise<Buffer>
{
  return new Promise( ( resolve, reject ) =>
  {
    const req = https.get( url, res =>
    {
      if ( res.statusCode >= 300 && res.statusCode < 400 && res.headers.location )
      {
        resolve( httpsGetBuffer( res.headers.location ) );
        return;
      }
      const chunks: Buffer[] = [];
      res.on( 'data', chunk => { chunks.push( chunk ); } );
      res.on( 'end', () => resolve( Buffer.concat( chunks ) ) );
    } );
    req.on( 'error', reject );
  } );
}

// ─── public router ────────────────────────────────────────────────────────────
//
// GET /get-font — returns a CSS file with @font-face rules
//
// Modes (mutually exclusive):
//   ?family=barlow                           → all files in directory
//   ?family=barlow&weights=400,700           → those weights + auto-italic if exists
//   ?family=barlow&variations=400,400 italic → exactly those variations

export const publicFontsRouter = Router();

publicFontsRouter.get( '/get-font', ( req: Request, res: Response ): void =>
{
  const familyParam = ( req.query.family as string | undefined )?.trim();
  if ( !familyParam )
  {
    res.status( 400 ).send( '/* family param required */' );
    return;
  }

  const meta = readMeta( familyParam );
  if ( !meta )
  {
    res.status( 404 ).send( `/* font family '${familyParam}' not found */` );
    return;
  }

  const blocks: string[] = [];

  if ( req.query.variations )
  {
    const vars = ( req.query.variations as string )
      .split( ',' )
      .map( v => v.trim().toLowerCase() );

    for ( const v of vars )
    {
      const italic = v.endsWith( ' italic' );
      const weight = italic ? v.slice( 0, -7 ).trim() : v;
      if ( fontFileExists( meta.family, weight, italic ) )
        blocks.push( buildFontFace( meta.family, weight, italic ) );
    }
  }
  else if ( req.query.weights )
  {
    const weights = ( req.query.weights as string )
      .split( ',' )
      .map( w => w.trim().toLowerCase() );

    for ( const w of weights )
    {
      if ( fontFileExists( meta.family, w, false ) )
        blocks.push( buildFontFace( meta.family, w, false ) );
      if ( fontFileExists( meta.family, w, true ) )
        blocks.push( buildFontFace( meta.family, w, true ) );
    }
  }
  else
  {
    for ( const w of meta.weights )
      blocks.push( buildFontFace( meta.family, w, false ) );
    for ( const w of meta.italics )
      blocks.push( buildFontFace( meta.family, w, true ) );
  }

  res
    .set( 'Content-Type', 'text/css; charset=utf-8' )
    .set( 'Cache-Control', 'public, max-age=86400' )
    .send( blocks.join( '\n\n' ) );
} );

// ─── api router (auth-gated, mounted at /api/fonts) ──────────────────────────

export const apiFontsRouter = Router();

// GET / — list all available font families
apiFontsRouter.get( '/', ( _req: Request, res: Response ): void =>
{
  if ( !fs.existsSync( FONTS_DIR ) )
  {
    res.json( [] );
    return;
  }

  const families = fs.readdirSync( FONTS_DIR, { withFileTypes: true } )
    .filter( d => d.isDirectory() )
    .map( d =>
    {
      const meta = readMeta( d.name );
      return meta ?? { family: d.name, weights: [], italics: [] };
    } );

  res.json( families );
} );

// POST /download — fetch from Google Fonts and save to storage
apiFontsRouter.post( '/download', async ( req: Request, res: Response ): Promise<void> =>
{
  const { family, weights } = req.body as { family: string; weights?: number[] };

  if ( !family || typeof family !== 'string' )
  {
    res.status( 400 ).json( { error: 'family is required' } );
    return;
  }

  const requestedWeights = ( weights && weights.length > 0 ) ? weights : ALL_WEIGHTS;

  const wghts     = requestedWeights.map( w => `0,${w};1,${w}` ).join( ';' );
  const googleUrl = `https://fonts.googleapis.com/css2?family=${encodeURIComponent( family )}:ital,wght@${wghts}&display=swap`;

  let css: string;
  try
  {
    css = await httpsGet( googleUrl, { 'User-Agent': GOOGLE_FONTS_UA } );
  }
  catch ( err )
  {
    res.status( 502 ).json( { error: 'Failed to reach Google Fonts', detail: String( err ) } );
    return;
  }

  if ( css.trim() === '' )
  {
    res.status( 404 ).json( { error: `Font family '${family}' not found on Google Fonts` } );
    return;
  }

  const faceRegex  = /@font-face\s*\{([^}]+)\}/g;
  const urlRegex   = /src:\s*url\(([^)]+)\)/;
  const weightRx   = /font-weight:\s*(\d+)/;
  const styleRx    = /font-style:\s*(normal|italic)/;

  const dir = fontsDir( family );
  fs.mkdirSync( dir, { recursive: true } );

  const meta: FontMeta   = { family, weights: [], italics: [] };
  const downloaded: string[] = [];

  let match: RegExpExecArray | null;
  while ( ( match = faceRegex.exec( css ) ) !== null )
  {
    const block       = match[1];
    const urlMatch    = urlRegex.exec( block );
    const weightMatch = weightRx.exec( block );
    const styleMatch  = styleRx.exec( block );

    if ( !urlMatch || !weightMatch || !styleMatch ) continue;

    const fontUrl  = urlMatch[1].trim();
    const weight   = weightMatch[1];
    const italic   = styleMatch[1] === 'italic';
    const fileName = italic ? `${weight}-italic.woff2` : `${weight}.woff2`;

    try
    {
      const buffer = await httpsGetBuffer( fontUrl );
      fs.writeFileSync( path.join( dir, fileName ), buffer );
      downloaded.push( fileName );

      if ( italic )
      {
        if ( !meta.italics.includes( weight ) ) meta.italics.push( weight );
      }
      else
      {
        if ( !meta.weights.includes( weight ) ) meta.weights.push( weight );
      }
    }
    catch
    {
      // skip individual file failures
    }
  }

  meta.weights.sort( ( a, b ) => Number( a ) - Number( b ) );
  meta.italics.sort( ( a, b ) => Number( a ) - Number( b ) );
  writeMeta( meta );

  res.json( { ok: true, family, downloaded } );
} );