import type { XtermTerminal, PromptFinder, PromptPosition } from './types.js';

/**
 * Find the prompt in the terminal buffer using the configured strategy.
 * Scans bottom-up through the viewport to find the most recent prompt.
 *
 * @returns The prompt position (viewport-relative), or `null` if not found.
 */
export function findPrompt(terminal: XtermTerminal, finder: PromptFinder): PromptPosition | null {
  try {
    const buffer = terminal.buffer.active;
    const viewportTop = buffer.viewportY;

    switch (finder.type) {
      case 'character': {
        for (let row = terminal.rows - 1; row >= 0; row--) {
          const line = buffer.getLine(viewportTop + row);
          if (!line) continue;
          const text = line.translateToString(true);
          const idx = text.lastIndexOf(finder.char);
          if (idx >= 0) return { row, col: idx };
        }
        return null;
      }

      case 'regex': {
        // Create a fresh non-global regex to avoid lastIndex mutation
        // and ensure .match() returns a single result with .index
        const pattern = finder.pattern;
        const safePattern = pattern.global ? new RegExp(pattern.source, pattern.flags.replace('g', '')) : pattern;
        for (let row = terminal.rows - 1; row >= 0; row--) {
          const line = buffer.getLine(viewportTop + row);
          if (!line) continue;
          const text = line.translateToString(true);
          const match = text.match(safePattern);
          if (match) {
            const col = match.index ?? 0;
            return { row, col };
          }
        }
        return null;
      }

      case 'custom':
        return finder.find(terminal);

      default:
        return null;
    }
  } catch {
    return null;
  }
}

/**
 * Read text after the prompt position on the same line.
 *
 * @param terminal - The xterm.js terminal instance
 * @param prompt - The prompt position in the viewport
 * @param offset - Characters to skip after the prompt marker (e.g., 2 for "> ")
 * @returns The text after the prompt, trimmed. Empty string if nothing found.
 */
export function readTextAfterPrompt(terminal: XtermTerminal, prompt: PromptPosition, offset: number): string {
  try {
    const buffer = terminal.buffer.active;
    const absRow = buffer.viewportY + prompt.row;
    const line = buffer.getLine(absRow);
    if (!line) return '';
    const lineText = line.translateToString(true);
    return lineText.slice(prompt.col + offset).trimEnd();
  } catch {
    return '';
  }
}