'use strict'

const fs = require('fs')
const path = require('path')
const { desktopFileFor, readDesktopEntry, findIconFile, pngOrSvg } = require('./linuxapp')

function rvaToOffset(sections, rva) {
  for (const s of sections) {
    if (rva >= s.va && rva < s.va + (s.vs || s.rawSize)) return rva - s.va + s.raw
  }
  return null
}

function dirEntries(buf, dirOff) {
  const named = buf.readUInt16LE(dirOff + 12)
  const ids = buf.readUInt16LE(dirOff + 14)
  const out = []
  for (let i = 0; i < named + ids; i++) {
    const e = dirOff + 16 + i * 8
    const nameOrId = buf.readUInt32LE(e)
    const value = buf.readUInt32LE(e + 4)
    out.push({ id: nameOrId & 0x7fffffff, isName: (nameOrId & 0x80000000) !== 0, value, isDir: (value & 0x80000000) !== 0 })
  }
  return out
}

function parseIcons(buf) {
  try {
    if (buf.length < 64 || buf.readUInt16LE(0) !== 0x5a4d) return null
    const peOff = buf.readUInt32LE(0x3c)
    if (peOff + 24 > buf.length || buf.readUInt32LE(peOff) !== 0x00004550) return null
    const numSections = buf.readUInt16LE(peOff + 6)
    const optSize = buf.readUInt16LE(peOff + 20)
    const optOff = peOff + 24
    const magic = buf.readUInt16LE(optOff)
    const resRva = magic === 0x20b ? buf.readUInt32LE(optOff + 128) : buf.readUInt32LE(optOff + 112)
    if (!resRva) return []

    const secOff = optOff + optSize
    const sections = []
    for (let i = 0; i < numSections; i++) {
      const s = secOff + i * 40
      sections.push({
        va: buf.readUInt32LE(s + 12),
        vs: buf.readUInt32LE(s + 8),
        rawSize: buf.readUInt32LE(s + 16),
        raw: buf.readUInt32LE(s + 20)
      })
    }

    const rootOff = rvaToOffset(sections, resRva)
    if (rootOff == null) return []

    const typeEntry = dirEntries(buf, rootOff).find(e => e.id === 3 && e.isDir)
    if (!typeEntry) return []
    const iconDirOff = rvaToOffset(sections, resRva + (typeEntry.value & 0x7fffffff))
    if (iconDirOff == null) return []

    const iconDatas = []
    for (const nameEntry of dirEntries(buf, iconDirOff)) {
      if (!nameEntry.isDir) continue
      const langDirOff = rvaToOffset(sections, resRva + (nameEntry.value & 0x7fffffff))
      if (langDirOff == null) continue
      const langEntry = dirEntries(buf, langDirOff)[0]
      if (!langEntry || langEntry.isDir) continue
      const dataEntryOff = rvaToOffset(sections, resRva + langEntry.value)
      if (dataEntryOff == null) continue
      const dataRva = buf.readUInt32LE(dataEntryOff)
      const dataSize = buf.readUInt32LE(dataEntryOff + 4)
      const dataOff = rvaToOffset(sections, dataRva)
      if (dataOff == null || !dataSize) continue
      iconDatas.push({ id: nameEntry.id, buf: Buffer.from(buf.subarray(dataOff, dataOff + dataSize)) })
    }
    if (!iconDatas.length) return []

    const groupEntry = dirEntries(buf, rootOff).find(e => e.id === 14 && e.isDir)
    if (groupEntry) {
      const grpDirOff = rvaToOffset(sections, resRva + (groupEntry.value & 0x7fffffff))
      if (grpDirOff != null) {
        for (const nameEntry of dirEntries(buf, grpDirOff)) {
          if (!nameEntry.isDir) continue
          const langDirOff = rvaToOffset(sections, resRva + (nameEntry.value & 0x7fffffff))
          if (langDirOff == null) continue
          const langEntry = dirEntries(buf, langDirOff)[0]
          if (!langEntry || langEntry.isDir) continue
          const dataEntryOff = rvaToOffset(sections, resRva + langEntry.value)
          if (dataEntryOff == null) continue
          const dataRva = buf.readUInt32LE(dataEntryOff)
          const dataSize = buf.readUInt32LE(dataEntryOff + 4)
          const dataOff = rvaToOffset(sections, dataRva)
          if (dataOff == null || !dataSize) continue
          const grp = buf.subarray(dataOff, dataOff + dataSize)
          if (grp.length < 6) continue
          const count = grp.readUInt16LE(4)
          const best = { area: -1, buf: null }
          for (let i = 0; i < count; i++) {
            const e = 6 + i * 14
            const w = grp.readUInt8(e) || 256
            const h = grp.readUInt8(e + 1) || 256
            const id = grp.readUInt16LE(e + 12)
            const icon = iconDatas.find(ic => ic.id === id)
            if (icon && w * h > best.area) {
              best.area = w * h
              best.buf = icon.buf
            }
          }
          if (best.buf) return [best.buf]
        }
      }
    }
    return [iconDatas.reduce((a, b) => (b.buf.length > a.buf.length ? b : a)).buf]
  } catch {
    return null
  }
}

function pngSize(img) {
  if (img.length > 24 && img.readUInt32BE(0) === 0x89504e47) {
    return { w: img.readUInt32BE(16), h: img.readUInt32BE(20) }
  }
  return null
}

// RT_ICON payloads are BITMAPINFOHEADER bitmaps; read real dimensions from
// there (ICONDIRENTRY-style first bytes yield garbage).
function bmpDims(img) {
  if (img.length < 12) return null
  const biSize = img.readUInt32LE(0)
  if (biSize === 12) {
    // BITMAPCOREHEADER (old icons): WORD width/height/planes/bitcount
    const w = img.readUInt16LE(4)
    const h = Math.floor(img.readUInt16LE(6) / 2)
    const planes = img.readUInt16LE(8) || 1
    const bpp = img.readUInt16LE(10) || 32
    const colors = bpp <= 8 ? 1 << bpp : 0
    if (w > 0 && h > 0 && w <= 1024 && h <= 1024) return { w, h, planes, bpp, colors }
    return null
  }
  if (biSize >= 40 && biSize <= 124 && img.length > 40) {
    const w = img.readUInt32LE(4)
    const h = Math.floor(img.readUInt32LE(8) / 2)
    const planes = img.readUInt16LE(12) || 1
    const bpp = img.readUInt16LE(14) || 32
    const colors = img.readUInt32LE(32) || (bpp <= 8 ? 1 << bpp : 0)
    if (w > 0 && h > 0 && w <= 1024 && h <= 1024) return { w, h, planes, bpp, colors }
  }
  return null
}

function buildIco(images) {
  const header = Buffer.alloc(6)
  header.writeUInt16LE(0, 0)
  header.writeUInt16LE(1, 2)
  header.writeUInt16LE(images.length, 4)
  const metas = []
  const datas = []
  let offset = 6 + images.length * 16
  for (const img of images) {
    let w, h, colors = 0, planes = 1, bpp = 32
    if (img.readUInt32BE(0) === 0x89504e47) {
      const dim = pngSize(img) || { w: 256, h: 256 }
      w = dim.w
      h = dim.h
    } else {
      const dims = bmpDims(img)
      if (dims) {
        w = dims.w
        h = dims.h
        colors = dims.colors
        planes = dims.planes
        bpp = dims.bpp
      } else {
        // legacy fallback: ICONDIRENTRY-style first bytes (PNG-era heuristic)
        w = img.readUInt8(0) || 256
        h = img.readUInt8(1) || 256
        colors = img.readUInt8(2)
        planes = img.length > 4 ? img.readUInt16LE(4) || 1 : 1
        bpp = img.length > 6 ? img.readUInt16LE(6) || 32 : 32
      }
    }
    const meta = Buffer.alloc(16)
    meta.writeUInt8(w >= 256 ? 0 : w, 0)
    meta.writeUInt8(h >= 256 ? 0 : h, 1)
    // 0 in the ICO dir entry means "256+ colors" (palette implied by bpp)
    meta.writeUInt8(colors >= 256 ? 0 : colors, 2)
    meta.writeUInt8(0, 3)
    meta.writeUInt16LE(planes, 4)
    meta.writeUInt16LE(bpp, 6)
    meta.writeUInt32LE(img.length, 8)
    meta.writeUInt32LE(offset, 12)
    metas.push(meta)
    datas.push(img)
    offset += img.length
  }
  return Buffer.concat([header, ...metas, ...datas])
}

function extractIconFromExe(exePath, outPath) {
  try {
    const buf = fs.readFileSync(exePath)
    const icon = parseIcons(buf)
    if (!icon || !icon.length) return { ok: false, error: 'no-icon' }
    const ico = buildIco(icon)
    fs.mkdirSync(path.dirname(outPath), { recursive: true })
    fs.writeFileSync(outPath, ico)
    return { ok: true, path: outPath }
  } catch (err) {
    return { ok: false, error: String(err && err.message || err) }
  }
}

// Native Linux apps carry no icon inside the binary: it comes from the
// .desktop entry (Icon=), an image next to the program, or the theme.
// `outBase` is a path without extension; the sniffed one is appended.
function iconFromLinuxApp(exePath, outBase) {
  try {
    const desktop = desktopFileFor(exePath)
    const entry = desktop ? readDesktopEntry(desktop) : null
    const baseDir = desktop ? path.dirname(desktop) : path.dirname(exePath)
    let source = findIconFile(entry && entry.Icon, baseDir)
    if (!source) {
      // no .desktop: a same-named image (or the AppImage .DirIcon) next to it
      const dir = path.dirname(exePath)
      const stem = path.basename(exePath).replace(/\.(appimage|sh|bin)$/i, '')
      for (const name of [stem + '.png', stem + '.svg', '.DirIcon', 'icon.png', 'icon.svg']) {
        const candidate = path.join(dir, name)
        if (pngOrSvg(candidate)) {
          source = candidate
          break
        }
      }
    }
    if (!source) return { ok: false, error: 'no-icon' }
    const outPath = `${outBase}.${pngOrSvg(source)}`
    fs.mkdirSync(path.dirname(outPath), { recursive: true })
    fs.copyFileSync(source, outPath)
    return { ok: true, path: outPath }
  } catch (err) {
    return { ok: false, error: String((err && err.message) || err) }
  }
}

module.exports = { extractIconFromExe, iconFromLinuxApp, parseIcons, buildIco }