import * as vscode from "vscode"
import * as fs from "fs/promises"
import * as path from "path"
import { Browser, Page, ScreenshotOptions, TimeoutError, launch } from "puppeteer-core"
import * as cheerio from "cheerio"
import TurndownService from "turndown"
// @ts-ignore
import PCR from "puppeteer-chromium-resolver"
import pWaitFor from "p-wait-for"
import delay from "delay"

interface PCRStats {
	puppeteer: { launch: typeof launch }
	executablePath: string
}

export class UrlContentFetcher {
	private context: vscode.ExtensionContext
	private browser?: Browser
	private page?: Page

	constructor(context: vscode.ExtensionContext) {
		this.context = context
	}

	private async ensureChromiumExists(): Promise<PCRStats> {
		const globalStoragePath = this.context?.globalStorageUri?.fsPath
		if (!globalStoragePath) {
			throw new Error("Global storage uri is invalid")
		}

		const puppeteerDir = path.join(globalStoragePath, "puppeteer")
		const dirExists = await fs
			.access(puppeteerDir)
			.then(() => true)
			.catch(() => false)
		if (!dirExists) {
			await fs.mkdir(puppeteerDir, { recursive: true })
		}

		// if chromium doesn't exist, this will download it to path.join(puppeteerDir, ".chromium-browser-snapshots")
		// if it does exist it will return the path to existing chromium
		const stats: PCRStats = await PCR({
			downloadPath: puppeteerDir,
		})

		return stats
	}

	async launchBrowser(): Promise<void> {
		if (this.browser) {
			return
		}
		const stats = await this.ensureChromiumExists()
		this.browser = await stats.puppeteer.launch({
			args: [
				"--user-agent=Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36",
			],
			executablePath: stats.executablePath,
		})
		// (latest version of puppeteer does not add headless to user agent)
		this.page = await this.browser?.newPage()
	}

	async closeBrowser(): Promise<void> {
		await this.browser?.close()
		this.browser = undefined
		this.page = undefined
	}

	// must make sure to call launchBrowser before and closeBrowser after using this
	async urlToMarkdown(url: string): Promise<string> {
		if (!this.browser || !this.page) {
			throw new Error("Browser not initialized")
		}
		/*
		- networkidle2 is equivalent to playwright's networkidle where it waits until there are no more than 2 network connections for at least 500 ms.
		- domcontentloaded is when the basic DOM is loaded
		this should be sufficient for most doc sites
		*/
		await this.page.goto(url, { timeout: 10_000, waitUntil: ["domcontentloaded", "networkidle2"] })
		const content = await this.page.content()

		// use cheerio to parse and clean up the HTML
		const $ = cheerio.load(content)
		$("script, style, nav, footer, header").remove()

		// convert cleaned HTML to markdown
		const turndownService = new TurndownService()
		const markdown = turndownService.turndown($.html())

		return markdown
	}

	async urlToScreenshotAndLogs(url: string): Promise<{ screenshot: string; logs: string }> {
		if (!this.browser || !this.page) {
			throw new Error("Browser not initialized")
		}

		const logs: string[] = []
		let lastLogTs = Date.now()

		this.page.on("console", (msg) => {
			if (msg.type() === "log") {
				logs.push(msg.text())
			} else {
				logs.push(`[${msg.type()}] ${msg.text()}`)
			}
			lastLogTs = Date.now()
		})
		this.page.on("pageerror", (err) => {
			logs.push(`[Page Error] ${err.toString()}`)
			lastLogTs = Date.now()
		})

		try {
			// networkidle2 isn't good enough since page may take some time to load. we can assume locally running dev sites will reach networkidle0 in a reasonable amount of time
			await this.page.goto(url, { timeout: 7_000, waitUntil: ["domcontentloaded", "networkidle2"] })
			// await this.page.goto(url, { timeout: 10_000, waitUntil: "load" })
			await this.waitTillHTMLStable(this.page) // in case the page is loading more resources
		} catch (err) {
			if (!(err instanceof TimeoutError)) {
				logs.push(`[Navigation Error] ${err.toString()}`)
			}
		}

		// Wait for console inactivity, with a timeout
		await pWaitFor(() => Date.now() - lastLogTs >= 500, {
			timeout: 3_000,
			interval: 100,
		}).catch(() => {})

		// image cannot exceed 8_000 pixels
		const { pageHeight, pageWidth } = await this.page.evaluate(() => {
			const html: HTMLElement | null = document.documentElement
			const body: HTMLElement | null = document.body
			return {
				pageHeight: html?.scrollHeight || body?.scrollHeight,
				pageWidth: html?.clientWidth || body?.clientWidth,
			}
		})
		// const defaultViewport = this.page.viewport(); // width 800 height 600 by default
		let options: ScreenshotOptions = {
			// fullPage: true, // clip and fullPage are mutually exclusive
			encoding: "base64",
			// quality: 80,
			clip: {
				x: 0,
				y: 0,
				width: pageWidth,
				height: Math.min(pageHeight, 8_000),
			},
		}

		let screenshotBase64 = await this.page.screenshot({
			...options,
			type: "webp",
		})
		let screenshot = `data:image/webp;base64,${screenshotBase64}`

		if (!screenshotBase64) {
			console.log("webp screenshot failed, trying png")
			screenshotBase64 = await this.page.screenshot({
				...options,
				type: "png",
			})
			screenshot = `data:image/png;base64,${screenshotBase64}`
		}

		if (!screenshotBase64) {
			throw new Error("Failed to take screenshot.")
		}

		this.page.removeAllListeners()

		return {
			screenshot,
			logs: logs.join("\n"),
		}
	}

	// page.goto { waitUntil: "networkidle0" } may not ever resolve, and not waiting could return page content too early before js has loaded
	// https://stackoverflow.com/questions/52497252/puppeteer-wait-until-page-is-completely-loaded/61304202#61304202
	private async waitTillHTMLStable(page: Page, timeout = 5_000) {
		const checkDurationMsecs = 500 // 1000
		const maxChecks = timeout / checkDurationMsecs
		let lastHTMLSize = 0
		let checkCounts = 1
		let countStableSizeIterations = 0
		const minStableSizeIterations = 3

		while (checkCounts++ <= maxChecks) {
			let html = await page.content()
			let currentHTMLSize = html.length

			// let bodyHTMLSize = await page.evaluate(() => document.body.innerHTML.length)
			console.log("last: ", lastHTMLSize, " <> curr: ", currentHTMLSize)

			if (lastHTMLSize !== 0 && currentHTMLSize === lastHTMLSize) {
				countStableSizeIterations++
			} else {
				countStableSizeIterations = 0 //reset the counter
			}

			if (countStableSizeIterations >= minStableSizeIterations) {
				console.log("Page rendered fully...")
				break
			}

			lastHTMLSize = currentHTMLSize
			await delay(checkDurationMsecs)
		}
	}
}