package converter

import (
	"context"
	"os"
	"path/filepath"
	"runtime"
	"time"

	"github.com/chromedp/cdproto/page"
	"github.com/chromedp/chromedp"
)

type Converter struct {
	chromePath string
}

func NewConverter(chromePath string) *Converter {
	return &Converter{chromePath: chromePath}
}

func (c *Converter) Convert(imputFile, outputFile string) error {

	chromePath := c.getChromePath()
	htmlURL := "file://"

	switch runtime.GOOS {
	case "windows":
		htmlURL += "/"
	}

	// Convert to absolute path
	absPath, err := filepath.Abs(imputFile)
	if err != nil {
		return err
	}

	htmlURL += filepath.ToSlash(absPath)

	opts := append(chromedp.DefaultExecAllocatorOptions[:],
		chromedp.ExecPath(chromePath),
		chromedp.NoSandbox,
		chromedp.Headless,
		chromedp.DisableGPU,
	)

	allocCtx, cancel := chromedp.NewExecAllocator(context.Background(), opts...)
	defer cancel()
	ctx, cancel := chromedp.NewContext(allocCtx)
	defer cancel()

	ctx, cancel = context.WithTimeout(ctx, 60*time.Second)
	defer cancel()

	var pdf []byte
	err = chromedp.Run(ctx,
		chromedp.Navigate(htmlURL),
		chromedp.WaitReady("body", chromedp.ByQuery),
		chromedp.ActionFunc(func(ctx context.Context) error {
			buf, _, err := page.PrintToPDF().
				WithPrintBackground(true).
				WithPaperWidth(8.27).
				WithPaperHeight(11.69).
				Do(ctx)
			if err != nil {
				return err
			}
			pdf = buf
			return nil
		}),
	)
	if err != nil {
		return err
	}

	// Save PDF to file
	if err := os.WriteFile(outputFile, pdf, 0644); err != nil {
		return err
	}
	return nil
}

// getChromePath checks for system Chrome, else falls back to bundled headless shell
func (c *Converter) getChromePath() string {
	// Candidate paths for system Chrome
	candidates := []string{}

	switch runtime.GOOS {
	case "windows":
		candidates = []string{
			`C:\Program Files\Google\Chrome\Application\chrome.exe`,
			`C:\Program Files (x86)\Google\Chrome\Application\chrome.exe`,
			`C:\Program Files\Chromium\Application\chrome.exe`,
		}
	case "darwin":
		candidates = []string{
			"/Applications/Google Chrome.app/Contents/MacOS/Google Chrome",
			"/Applications/Chromium.app/Contents/MacOS/Chromium",
		}
	default: // Linux
		candidates = []string{
			"/usr/bin/google-chrome",
			"/usr/bin/chromium-browser",
			"/usr/bin/chromium",
		}
	}

	// Check system paths first
	for _, path := range candidates {
		if _, err := os.Stat(path); err == nil {
			return path
		}
	}

	// Fallback: use bundled headless shell
	chromeExec := "chrome-headless-shell"
	if runtime.GOOS == "windows" {
		chromeExec += ".exe"
	}
	return filepath.Join(c.chromePath, chromeExec)
}