package pdf

import (
	"context"
	"fmt"
	"io"
	"time"

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

// Generator handles PDF generation using headless Chrome
type Generator struct {
	timeout time.Duration
}

// NewGenerator creates a new PDF generator with the specified timeout
func NewGenerator(timeout time.Duration) *Generator {
	if timeout == 0 {
		timeout = 30 * time.Second
	}
	return &Generator{
		timeout: timeout,
	}
}

// GenerateFromURL generates a PDF from a given URL
func (g *Generator) GenerateFromURL(ctx context.Context, url string) ([]byte, error) {
	// Create context with timeout
	ctx, cancel := context.WithTimeout(ctx, g.timeout)
	defer cancel()

	// Create chromedp context
	allocCtx, allocCancel := chromedp.NewContext(ctx)
	defer allocCancel()

	// Buffer to store PDF
	var pdfBuffer []byte

	// Run chromedp tasks
	err := chromedp.Run(allocCtx,
		// Navigate to URL
		chromedp.Navigate(url),

		// Wait for page to be ready
		chromedp.WaitReady("body"),

		// Small delay to ensure all content is loaded
		chromedp.Sleep(500*time.Millisecond),

		// Generate PDF with print-optimized settings
		chromedp.ActionFunc(func(ctx context.Context) error {
			var err error
			pdfBuffer, _, err = page.PrintToPDF().
				WithPrintBackground(true).
				WithPreferCSSPageSize(true).
				WithMarginTop(0).
				WithMarginBottom(0).
				WithMarginLeft(0).
				WithMarginRight(0).
				WithPaperWidth(8.27).  // A4 width in inches
				WithPaperHeight(11.69). // A4 height in inches
				Do(ctx)
			return err
		}),
	)

	if err != nil {
		return nil, fmt.Errorf("chromedp execution failed: %w", err)
	}

	if len(pdfBuffer) == 0 {
		return nil, fmt.Errorf("generated PDF is empty")
	}

	return pdfBuffer, nil
}

// StreamFromURL generates a PDF and writes it to the provided writer
func (g *Generator) StreamFromURL(ctx context.Context, url string, w io.Writer) error {
	pdfData, err := g.GenerateFromURL(ctx, url)
	if err != nil {
		return err
	}

	_, err = w.Write(pdfData)
	return err
}
