import { type ChildProcess, spawn } from 'node:child_process'
import { existsSync, mkdirSync } from 'node:fs'
import { homedir, platform } from 'node:os'
import { join } from 'node:path'
import { chromePath, localAppData } from '../consts.ts'
import { reclaimHomeDirPath } from '../paths.ts'

export interface LaunchOptions {
	/** Port for --remote-debugging-port. */
	port: number
	/** Path to user-data-dir. Created if missing. */
	profileDir: string
	/** If true, launch without a visible window (--headless=new). Useful
	 *  for tests and CI; user-driven flows want it false. */
	headless?: boolean
}

/**
 * Build the platform-specific list of Chromium-family binaries to probe.
 * Order matters: Chrome first, then Chromium, then Edge (Edge is
 * Chromium-based, supports CDP, and is preinstalled on Win 10/11 — a
 * useful fallback when Chrome itself isn't installed).
 *
 * On Windows we also probe the per-user Chrome install under
 * %LOCALAPPDATA%, which is what you get when Chrome was installed
 * without admin rights ("Install for me only"). Skipping this was the
 * #1 first-run failure observed in the field.
 */
function browserCandidates(): string[] {
	switch (platform()) {
		case 'darwin':
			return [
				'/Applications/Google Chrome.app/Contents/MacOS/Google Chrome',
				join(
					homedir(),
					'Applications/Google Chrome.app/Contents/MacOS/Google Chrome',
				),
				'/Applications/Chromium.app/Contents/MacOS/Chromium',
				'/Applications/Microsoft Edge.app/Contents/MacOS/Microsoft Edge',
			]
		case 'win32': {
			const appData =
				localAppData() ?? join(homedir(), 'AppData', 'Local')
			return [
			// System-wide Chrome
				'C:\\Program Files\\Google\\Chrome\\Application\\chrome.exe',
				'C:\\Program Files (x86)\\Google\\Chrome\\Application\\chrome.exe',
				// Per-user Chrome ("Install for me only")
				join(appData, 'Google', 'Chrome', 'Application', 'chrome.exe'),
				// Edge — Chromium-based, preinstalled on Win 10/11
				'C:\\Program Files\\Microsoft\\Edge\\Application\\msedge.exe',
				'C:\\Program Files (x86)\\Microsoft\\Edge\\Application\\msedge.exe',
			]
		}

		case 'linux':
			return [
				'/usr/bin/google-chrome',
				'/usr/bin/google-chrome-stable',
				'/usr/bin/chromium',
				'/usr/bin/chromium-browser',
				'/snap/bin/chromium',
				'/usr/bin/microsoft-edge',
			]
		default:
			return []
	}
}

export function defaultProfileDir(): string {
	return join(reclaimHomeDirPath(), 'chrome-profile')
}

export function findChromeBinary(): string {
	const candidates = browserCandidates()
	for(const c of candidates) {
		if(existsSync(c)) {
			return c
		}
	}

	throw new Error(
		`No Chromium-family browser found on ${platform()}. Tried:\n  ` +
			candidates.join('\n  ') +
		'\nSet RECLAIM_AGENT_CHROME_PATH to point at ' +
		'your chrome.exe / msedge.exe / chromium binary.',
	)
}

export function launchChrome(opts: LaunchOptions): ChildProcess {
	const binary = chromePath() ?? findChromeBinary()
	if(!existsSync(opts.profileDir)) {
		mkdirSync(opts.profileDir, { recursive: true })
	}

	const args = [
		`--remote-debugging-port=${opts.port}`,
		`--user-data-dir=${opts.profileDir}`,
		'--no-first-run',
		'--no-default-browser-check',
	]
	if(opts.headless) {
		args.push('--headless=new', '--disable-gpu')
	}

	const child = spawn(binary, args, {
		stdio: 'ignore',
		detached: false,
	})
	return child
}

export async function waitForCdpReady(
	port: number,
	timeoutMs = 10_000,
) {
	const deadline = Date.now() + timeoutMs
	while(Date.now() < deadline) {
		try {
			const res = await fetch(`http://127.0.0.1:${port}/json/version`)
			if(res.ok) {
				return
			}
		} catch{
			// retry
		}

		await new Promise<void>((r) => setTimeout(r, 150))
	}

	throw new Error(
		`Chrome CDP did not become ready on port ${port} within ${timeoutMs}ms`,
	)
}