/**
 * Read File Tool - Single file precise reading with optional line pagination
 *
 * Features:
 * - Read a single file with full content
 * - Line-based pagination with offset/limit
 * - Binary file detection
 */

import { z } from 'zod';
import type { ToolSchema, ToolResult } from '../types/tool.js';
import { existsSync, statSync } from 'fs';
import { relative } from 'path';
import { validatePath, getProjectRoot } from '../utils/path-validator.js';
import {
  MAX_CONTENT_LENGTH,
  readFileContent,
  type FileEntry,
  type ReadResult,
} from '../utils/file-reader.js';

const ParamsSchema = z.object({
  path: z.string().describe('Single file path to read'),
  offset: z.number().min(0).optional().describe('Line offset to start reading from (0-based)'),
  limit: z.number().min(1).optional().describe('Number of lines to read'),
});

type Params = z.infer<typeof ParamsSchema>;

export const schema: ToolSchema = {
  name: 'read_file',
  description: `Read a single file with optional line-based pagination.

Usage:
  read_file(path="file.ts")                        # Full content
  read_file(path="file.ts", offset=100, limit=50)  # Lines 100-149 (0-based)

Supports both absolute and relative paths. Relative paths are resolved from project root.
Use offset/limit for large file pagination.`,
  inputSchema: {
    type: 'object',
    properties: {
      path: {
        type: 'string',
        description: 'Single file path to read',
      },
      offset: {
        type: 'number',
        description: 'Line offset to start reading from (0-based)',
        minimum: 0,
      },
      limit: {
        type: 'number',
        description: 'Number of lines to read',
        minimum: 1,
      },
    },
    required: ['path'],
  },
};

export async function handler(params: Record<string, unknown>): Promise<ToolResult<ReadResult>> {
  const parsed = ParamsSchema.safeParse(params);
  if (!parsed.success) {
    return { success: false, error: `Invalid params: ${parsed.error.message}` };
  }

  const { path: filePath, offset, limit } = parsed.data;
  const cwd = getProjectRoot();
  const resolvedPath = await validatePath(filePath);

  if (!existsSync(resolvedPath)) {
    return { success: false, error: `File not found: ${filePath}` };
  }

  const stat = statSync(resolvedPath);
  if (!stat.isFile()) {
    return { success: false, error: `Not a file: ${filePath}. Use read_many_files for directories.` };
  }

  const { content, truncated, totalLines, lineRange } = readFileContent(resolvedPath, {
    maxLength: MAX_CONTENT_LENGTH,
    offset,
    limit,
  });

  const entry: FileEntry = {
    path: relative(cwd, resolvedPath) || filePath,
    size: stat.size,
    content,
    truncated,
    totalLines,
    lineRange,
  };

  let message = `Read 1 file`;
  if (lineRange) {
    message += ` [lines ${lineRange.start}-${lineRange.end} of ${totalLines}]`;
  }

  return {
    success: true,
    result: {
      files: [entry],
      totalFiles: 1,
      message,
    },
  };
}