/**
 * Bash command execution with streaming support and cancellation.
 *
 * This module provides a unified bash execution implementation used by:
 * - AgentSession.executeBash() for interactive and RPC modes
 * - Direct calls from modes that need bash execution
 */

import { randomBytes } from "node:crypto";
import { createWriteStream, type WriteStream } from "node:fs";
import { tmpdir } from "node:os";
import { join } from "node:path";
import { type ChildProcess, spawn } from "child_process";
import stripAnsi from "strip-ansi";
import { getShellConfig, killProcessTree, sanitizeBinaryOutput } from "../utils/shell.js";
import { DEFAULT_MAX_BYTES, truncateTail } from "./tools/truncate.js";

// ============================================================================
// Types
// ============================================================================

export interface BashExecutorOptions {
	/** Callback for streaming output chunks (already sanitized) */
	onChunk?: (chunk: string) => void;
	/** AbortSignal for cancellation */
	signal?: AbortSignal;
}

export interface BashResult {
	/** Combined stdout + stderr output (sanitized, possibly truncated) */
	output: string;
	/** Process exit code (undefined if killed/cancelled) */
	exitCode: number | undefined;
	/** Whether the command was cancelled via signal */
	cancelled: boolean;
	/** Whether the output was truncated */
	truncated: boolean;
	/** Path to temp file containing full output (if output exceeded truncation threshold) */
	fullOutputPath?: string;
}

// ============================================================================
// Implementation
// ============================================================================

/**
 * Execute a bash command with optional streaming and cancellation support.
 *
 * Features:
 * - Streams sanitized output via onChunk callback
 * - Writes large output to temp file for later retrieval
 * - Supports cancellation via AbortSignal
 * - Sanitizes output (strips ANSI, removes binary garbage, normalizes newlines)
 * - Truncates output if it exceeds the default max bytes
 *
 * @param command - The bash command to execute
 * @param options - Optional streaming callback and abort signal
 * @returns Promise resolving to execution result
 */
export function executeBash(command: string, options?: BashExecutorOptions): Promise<BashResult> {
	return new Promise((resolve, reject) => {
		const { shell, args } = getShellConfig();
		const child: ChildProcess = spawn(shell, [...args, command], {
			detached: true,
			stdio: ["ignore", "pipe", "pipe"],
		});

		// Track sanitized output for truncation
		const outputChunks: string[] = [];
		let outputBytes = 0;
		const maxOutputBytes = DEFAULT_MAX_BYTES * 2;

		// Temp file for large output
		let tempFilePath: string | undefined;
		let tempFileStream: WriteStream | undefined;
		let totalBytes = 0;

		// Handle abort signal
		const abortHandler = () => {
			if (child.pid) {
				killProcessTree(child.pid);
			}
		};

		if (options?.signal) {
			if (options.signal.aborted) {
				// Already aborted, don't even start
				child.kill();
				resolve({
					output: "",
					exitCode: undefined,
					cancelled: true,
					truncated: false,
				});
				return;
			}
			options.signal.addEventListener("abort", abortHandler, { once: true });
		}

		const decoder = new TextDecoder();

		const handleData = (data: Buffer) => {
			totalBytes += data.length;

			// Sanitize once at the source: strip ANSI, replace binary garbage, normalize newlines
			const text = sanitizeBinaryOutput(stripAnsi(decoder.decode(data, { stream: true }))).replace(/\r/g, "");

			// Start writing to temp file if exceeds threshold
			if (totalBytes > DEFAULT_MAX_BYTES && !tempFilePath) {
				const id = randomBytes(8).toString("hex");
				tempFilePath = join(tmpdir(), `pi-bash-${id}.log`);
				tempFileStream = createWriteStream(tempFilePath);
				// Write already-buffered chunks to temp file
				for (const chunk of outputChunks) {
					tempFileStream.write(chunk);
				}
			}

			if (tempFileStream) {
				tempFileStream.write(text);
			}

			// Keep rolling buffer of sanitized text
			outputChunks.push(text);
			outputBytes += text.length;
			while (outputBytes > maxOutputBytes && outputChunks.length > 1) {
				const removed = outputChunks.shift()!;
				outputBytes -= removed.length;
			}

			// Stream to callback if provided
			if (options?.onChunk) {
				options.onChunk(text);
			}
		};

		child.stdout?.on("data", handleData);
		child.stderr?.on("data", handleData);

		child.on("close", (code) => {
			// Clean up abort listener
			if (options?.signal) {
				options.signal.removeEventListener("abort", abortHandler);
			}

			if (tempFileStream) {
				tempFileStream.end();
			}

			// Combine buffered chunks for truncation (already sanitized)
			const fullOutput = outputChunks.join("");
			const truncationResult = truncateTail(fullOutput);

			// code === null means killed (cancelled)
			const cancelled = code === null;

			resolve({
				output: truncationResult.truncated ? truncationResult.content : fullOutput,
				exitCode: cancelled ? undefined : code,
				cancelled,
				truncated: truncationResult.truncated,
				fullOutputPath: tempFilePath,
			});
		});

		child.on("error", (err) => {
			// Clean up abort listener
			if (options?.signal) {
				options.signal.removeEventListener("abort", abortHandler);
			}

			if (tempFileStream) {
				tempFileStream.end();
			}

			reject(err);
		});
	});
}
