<?php

namespace App\Services\Tool\Tools;

use App\Services\Tool\Tool;
use InvalidArgumentException;

class FileReadTool implements Tool
{
    public function name(): string
    {
        return 'file_read';
    }

    public function description(): string
    {
        return '读取文件内容，支持指定行范围、编码和大文件分段读取。';
    }

    /**
     * @return array<string, mixed>
     */
    public function parameters(): array
    {
        return [
            'type' => 'object',
            'properties' => [
                'path' => [
                    'type' => 'string',
                    'description' => '要读取的文件路径（相对或绝对路径）。',
                ],
                'start_line' => [
                    'type' => 'integer',
                    'description' => '起始行号（从1开始），默认从第一行开始。',
                    'minimum' => 1,
                    'default' => 1,
                ],
                'end_line' => [
                    'type' => 'integer',
                    'description' => '结束行号（包含），默认读取到文件末尾。',
                    'minimum' => 1,
                ],
                'max_size' => [
                    'type' => 'integer',
                    'description' => '最大读取字节数（1-10MB），默认1MB，防止读取过大文件。',
                    'minimum' => 1,
                    'maximum' => 10485760,
                    'default' => 1048576,
                ],
                'encoding' => [
                    'type' => 'string',
                    'description' => '文件编码，默认UTF-8。',
                    'enum' => ['UTF-8', 'GBK', 'GB2312', 'ISO-8859-1'],
                    'default' => 'UTF-8',
                ],
            ],
            'required' => ['path'],
        ];
    }

    /**
     * @param array<string, mixed> $arguments
     * @return array<string, mixed>
     */
    public function execute(array $arguments): array
    {
        $path = $arguments['path'] ?? '';
        
        // 验证路径
        if (empty($path)) {
            throw new InvalidArgumentException('文件路径不能为空。');
        }

        // 安全检查：防止路径遍历攻击
        $realPath = realpath($path);
        if ($realPath === false) {
            throw new InvalidArgumentException("文件不存在：{$path}");
        }

        if (!is_file($realPath)) {
            throw new InvalidArgumentException("路径不是文件：{$path}");
        }

        if (!is_readable($realPath)) {
            throw new InvalidArgumentException("文件不可读：{$path}");
        }

        // 获取参数
        $startLine = max(1, (int)($arguments['start_line'] ?? 1));
        $endLine = isset($arguments['end_line']) ? max(1, (int)$arguments['end_line']) : null;
        $maxSize = min(10485760, max(1, (int)($arguments['max_size'] ?? 1048576)));
        $encoding = $arguments['encoding'] ?? 'UTF-8';

        // 检查文件大小
        $fileSize = filesize($realPath);
        if ($fileSize === false) {
            throw new InvalidArgumentException("无法获取文件大小：{$path}");
        }

        return $this->readFileContent($realPath, $startLine, $endLine, $maxSize, $encoding, $fileSize);
    }

    /**
     * 读取文件内容
     *
     * @param string $path
     * @param int $startLine
     * @param int|null $endLine
     * @param int $maxSize
     * @param string $encoding
     * @param int $fileSize
     * @return array<string, mixed>
     */
    private function readFileContent(
        string $path,
        int $startLine,
        ?int $endLine,
        int $maxSize,
        string $encoding,
        int $fileSize
    ): array {
        $result = [
            'path' => $path,
            'size' => $fileSize,
            'encoding' => $encoding,
        ];

        // 如果文件为空
        if ($fileSize === 0) {
            $result['content'] = '';
            $result['lines_read'] = 0;
            $result['truncated'] = false;
            return $result;
        }

        // 读取文件
        $handle = fopen($path, 'r');
        if ($handle === false) {
            throw new InvalidArgumentException("无法打开文件：{$path}");
        }

        try {
            return $this->readLines($handle, $startLine, $endLine, $maxSize, $encoding, $result);
        } finally {
            fclose($handle);
        }
    }

    /**
     * 按行读取文件
     *
     * @param resource $handle
     * @param int $startLine
     * @param int|null $endLine
     * @param int $maxSize
     * @param string $encoding
     * @param array<string, mixed> $result
     * @return array<string, mixed>
     */
    private function readLines(
        $handle,
        int $startLine,
        ?int $endLine,
        int $maxSize,
        string $encoding,
        array $result
    ): array {
        $lines = [];
        $currentLine = 0;
        $bytesRead = 0;
        $truncated = false;

        while (($line = fgets($handle)) !== false) {
            $currentLine++;

            // 跳过起始行之前的内容
            if ($currentLine < $startLine) {
                continue;
            }

            // 检查是否超过结束行
            if ($endLine !== null && $currentLine > $endLine) {
                break;
            }

            // 检查大小限制
            $lineLength = strlen($line);
            if ($bytesRead + $lineLength > $maxSize) {
                $truncated = true;
                break;
            }

            $lines[] = $line;
            $bytesRead += $lineLength;
        }

        $content = implode('', $lines);

        // 编码转换
        if ($encoding !== 'UTF-8' && function_exists('mb_convert_encoding')) {
            $content = mb_convert_encoding($content, 'UTF-8', $encoding);
        }

        $result['content'] = $content;
        $result['lines_read'] = count($lines);
        $result['start_line'] = $startLine;
        $result['end_line'] = $endLine ?? $currentLine;
        $result['truncated'] = $truncated;
        $result['bytes_read'] = $bytesRead;

        if ($truncated) {
            $result['warning'] = "内容已截断，已读取 {$bytesRead} 字节（限制：{$maxSize} 字节）";
        }

        return $result;
    }
}