import type { TextTransformResult } from './source-formatting'

/**
 * Map from MIME type to file extension for image paste.
 * Only covers common image types; unknown types default to .png.
 */
const MIME_TO_EXTENSION: Record<string, string> = {
  'image/png': 'png',
  'image/jpeg': 'jpg',
  'image/gif': 'gif',
  'image/webp': 'webp',
  'image/svg+xml': 'svg',
  'image/bmp': 'bmp',
  'image/x-icon': 'ico',
}

/**
 * Get file extension for a MIME type.
 * Returns 'png' for unknown types (safe default for pasted images).
 */
export function extensionFromMimeType(mimeType: string): string {
  return MIME_TO_EXTENSION[mimeType] ?? 'png'
}

/**
 * Generate a filename for a pasted image.
 * Format: "Pasted image YYYYMMDDHHMMSSmmm.ext"
 *
 * Includes milliseconds to avoid collisions on rapid pastes within the same second.
 *
 * @param mimeType - The image MIME type (e.g., 'image/png')
 * @param now - Timestamp in ms (defaults to Date.now(), injectable for testing)
 */
export function generateImageFilename(mimeType: string, now?: number): string {
  const d = new Date(now ?? Date.now())
  const pad2 = (n: number) => String(n).padStart(2, '0')
  const pad3 = (n: number) => String(n).padStart(3, '0')
  const timestamp = [
    d.getFullYear(),
    pad2(d.getMonth() + 1),
    pad2(d.getDate()),
    pad2(d.getHours()),
    pad2(d.getMinutes()),
    pad2(d.getSeconds()),
    pad3(d.getMilliseconds()),
  ].join('')
  const ext = extensionFromMimeType(mimeType)
  return `Pasted image ${timestamp}.${ext}`
}

/**
 * Check if a DataTransfer contains an image file.
 *
 * Returns true when:
 * 1. clipboardData has 'Files' in types
 * 2. At least one item has an image/* MIME type with kind 'file'
 *
 * NOTE: We intentionally do NOT exclude clipboards that also contain
 * text/plain or text/html. Mobile browsers (Firefox, Safari, Chrome)
 * routinely include text types alongside image files when pasting images.
 * The previous "text takes priority" heuristic blocked all mobile image
 * paste. If an image file is present, we treat it as an image paste.
 *
 * KNOWN LIMITATION: Firefox Android delivers empty clipboardData for
 * JPEG images (types=[], files=0, items=[]). PNG paste works. This is a
 * browser-level limitation — no web API (clipboardData, beforeinput,
 * navigator.clipboard.read(), MutationObserver) exposes JPEG data.
 * Use the toolbar photo picker button as a workaround on Firefox Android.
 */
export function hasClipboardImage(dataTransfer: DataTransfer | null): boolean {
  if (!dataTransfer) return false
  if (!dataTransfer.types.includes('Files')) return false

  // Check for image/* file items (must be kind 'file', not 'string')
  for (let i = 0; i < dataTransfer.items.length; i++) {
    const item = dataTransfer.items[i]
    if (item.type.startsWith('image/') && item.kind === 'file') return true
  }
  return false
}

/**
 * Extract the first image file from a DataTransfer.
 * Returns null if no image file is found.
 */
export function getImageFile(dataTransfer: DataTransfer): File | null {
  for (let i = 0; i < dataTransfer.items.length; i++) {
    const item = dataTransfer.items[i]
    if (item.type.startsWith('image/') && item.kind === 'file') {
      return item.getAsFile()
    }
  }
  return null
}

/**
 * Read a File as a Uint8Array.
 */
export function readFileAsUint8Array(file: File): Promise<Uint8Array> {
  return new Promise((resolve, reject) => {
    const reader = new FileReader()
    reader.onload = () => {
      if (reader.result instanceof ArrayBuffer) {
        resolve(new Uint8Array(reader.result))
      } else {
        reject(new Error('FileReader did not return ArrayBuffer'))
      }
    }
    reader.onerror = () => reject(reader.error ?? new Error('FileReader failed'))
    reader.onabort = () => reject(new Error('FileReader aborted'))
    reader.readAsArrayBuffer(file)
  })
}

/**
 * Sanitize a filename for safe use in wikilink syntax.
 * Strips characters that would break `![[filename]]` parsing: `[`, `]`, `|`, `#`, `^`.
 * Replaces them with hyphens, then collapses consecutive hyphens.
 */
export function sanitizeFilename(name: string): string {
  const sanitized = name
    .replace(/[[\]|#^]/g, '-')
    .replace(/-{2,}/g, '-')
    .replace(/^-|-$/g, '')
  // Guard against filenames that become empty after sanitization
  // (e.g., '[[[' → ''). Fall back to a timestamp-based name.
  return sanitized || `file-${Date.now()}`
}

/**
 * Insert ![[filename]] text at the cursor position in source mode.
 * Returns a TextTransformResult compatible with applySourceFormat.
 *
 * If start !== end, the selected text is replaced with the embed.
 *
 * @param text - Full document text
 * @param start - Selection start (absolute offset)
 * @param end - Selection end (absolute offset)
 * @param filename - The filename to embed
 */
export function insertEmbedAtCursor(
  _text: string,
  start: number,
  end: number,
  filename: string,
): TextTransformResult {
  const embed = `![[${filename}]]`
  const cursorPos = start + embed.length
  return {
    changes: { from: start, to: end, insert: embed },
    selectionStart: cursorPos,
    selectionEnd: cursorPos,
  }
}