package pdf

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

	"github.com/chromedp/cdproto/network"
	"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 options for headless mode (especially for CI environments)
	opts := append(chromedp.DefaultExecAllocatorOptions[:],
		chromedp.NoSandbox,
		chromedp.DisableGPU,
	)

	// Create exec allocator with custom options
	allocCtx, allocCancel := chromedp.NewExecAllocator(ctx, opts...)
	defer allocCancel()

	// Create chromedp context
	browserCtx, browserCancel := chromedp.NewContext(allocCtx)
	defer browserCancel()

	// Use browserCtx instead of allocCtx for chromedp operations
	allocCtx = browserCtx

	// 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
}

// RenderMode determines how the PDF is rendered
type RenderMode string

const (
	// RenderModePrint uses @media print CSS (clean, print-friendly)
	RenderModePrint RenderMode = "print"
	// RenderModeScreen uses @media screen CSS (long, full page with sidebars)
	RenderModeScreen RenderMode = "screen"
)

// GenerateFromURLWithCookies generates a PDF from a given URL with custom cookies
func (g *Generator) GenerateFromURLWithCookies(ctx context.Context, url string, cookies map[string]string) ([]byte, error) {
	return g.GenerateFromURLWithOptions(ctx, url, cookies, RenderModePrint)
}

// GenerateFromURLWithOptions generates a PDF with custom cookies and render mode
func (g *Generator) GenerateFromURLWithOptions(ctx context.Context, url string, cookies map[string]string, mode RenderMode) ([]byte, error) {
	// Create context with timeout
	ctx, cancel := context.WithTimeout(ctx, g.timeout)
	defer cancel()

	// Create chromedp options for headless mode (especially for CI environments)
	opts := append(chromedp.DefaultExecAllocatorOptions[:],
		chromedp.NoSandbox,
		chromedp.DisableGPU,
	)

	// Create exec allocator with custom options
	execCtx, execCancel := chromedp.NewExecAllocator(ctx, opts...)
	defer execCancel()

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

	// Buffer to store PDF
	var pdfBuffer []byte

	// Build tasks - set cookies BEFORE navigation
	var tasks chromedp.Tasks

	// Add cookies if provided - must be done before navigation
	if len(cookies) > 0 {
		tasks = append(tasks, chromedp.ActionFunc(func(ctx context.Context) error {
			// Set cookies with domain (extract from URL)
			// For localhost:1999, domain should be "localhost"
			domain := "localhost"

			for name, value := range cookies {
				expr := network.SetCookie(name, value).
					WithDomain(domain).
					WithPath("/").
					WithHTTPOnly(true).
					WithSecure(false). // Set to true in production with HTTPS
					WithSameSite(network.CookieSameSiteStrict)

				if err := expr.Do(ctx); err != nil {
					return fmt.Errorf("failed to set cookie %s: %w", name, err)
				}
			}
			return nil
		}))
	}

	// Navigate to URL
	tasks = append(tasks, chromedp.Navigate(url))

	// Wait for page to be ready
	tasks = append(tasks,
		chromedp.WaitReady("body"),
		// Small delay to ensure all content is loaded
		chromedp.Sleep(500*time.Millisecond),
	)

	// Apply mode-specific customizations
	if mode == RenderModeScreen {
		// For long version: Use print media for compact layout, but show sidebars
		// Print CSS hides sidebars - we override that to show them
		// UI elements remain hidden (already handled by print CSS)

		// Wait for page to fully render
		tasks = append(tasks, chromedp.Sleep(500*time.Millisecond))

		// Check if this is a short version (to apply compact sidebar fonts)
		// The length parameter is passed as a cookie, not in the URL
		isShortVersion := cookies["cv-length"] == "short"

		// Inject CSS to show sidebars AND restore their positioning
		tasks = append(tasks, chromedp.ActionFunc(func(ctx context.Context) error {
			// Base CSS for all versions with sidebars
			baseSidebarCSS := `
				(function() {
					const style = document.createElement('style');
					style.textContent = '@media print { ' +
						// Override all width constraints for full page width
						'.cv-page, .cv-paper, .cv-container { max-width: 100% !important; width: 100% !important; margin: 0 !important; padding: 0 !important; transform: none !important; } ' +

						// Override print.css blocking display
						'.cv-sidebar, .cv-sidebar-left, .cv-sidebar-right { display: block !important; } ' +

					// Hide accordion header (web mobile UI element)
					'.sidebar-accordion-header { display: none !important; } ' +

					// Force page break before page 2 (start right sidebar on new page)
					'.page-2 { page-break-before: always !important; break-before: page !important; } ' +

						// Grid Layout - Match web's 2-column approach (no wasted space!)
						'.page-content { ' +
							'display: grid !important; ' +
							'gap: 0 !important; ' +
							'width: 100% !important; ' +
							'max-width: 100% !important; ' +
						'} ' +

						// Page 1: Left sidebar (25%) + Main (75%) - NO right space
						'.page-1 .page-content { ' +
							'grid-template-columns: 25% 75% !important; ' +
						'} ' +

						// Page 2: Main (75%) + Right sidebar (25%) - NO left space
						'.page-2 .page-content { ' +
							'grid-template-columns: 75% 25% !important; ' +
						'} ' +

						// Sidebar positioning and padding
						'.cv-sidebar-left { grid-column: 1 !important; padding: 12mm 8mm !important; } ' +
						'.cv-sidebar-right { grid-column: 2 !important; padding: 12mm 8mm !important; } ' +

						// Main content positioning (different column for each page)
						'.page-1 .cv-main { grid-column: 2 !important; max-width: none !important; width: 100% !important; padding: 12mm 10mm !important; } ' +
						'.page-2 .cv-main { grid-column: 1 !important; max-width: none !important; width: 100% !important; padding: 12mm 10mm !important; } '`

			// Add compact font styles ONLY for short version
			compactFontCSS := ""
			if isShortVersion {
				compactFontCSS = ` +
						// Compact sidebar fonts (SHORT VERSION ONLY) - very subtle reduction to let content flow naturally
						'.cv-sidebar * { font-size: 0.96em !important; line-height: 1.4 !important; } ' +
						'.cv-sidebar h3 { font-size: 0.98em !important; margin: 0.4em 0 !important; padding: 0 !important; } ' +
						'.cv-sidebar h4 { font-size: 0.96em !important; margin: 0.35em 0 !important; padding: 0 !important; } ' +
						'.cv-sidebar p, .cv-sidebar li { font-size: 0.94em !important; line-height: 1.4 !important; margin: 0.3em 0 !important; padding: 0 !important; } ' +
						'.cv-sidebar ul, .cv-sidebar ol { margin: 0.4em 0 0.4em 1.2em !important; padding: 0 !important; } ' +
						'.cv-sidebar li { margin-bottom: 0.25em !important; } ' +
						'.cv-sidebar section { margin-bottom: 0.8em !important; } '`
			}

			showSidebarsScript := baseSidebarCSS + compactFontCSS + ` +
					'}';
					document.head.appendChild(style);
				})();
			`
			return chromedp.Evaluate(showSidebarsScript, nil).Do(ctx)
		}))
	}
	// For RenderModePrint (clean version): use default print media (@media print CSS)
	// which hides both UI elements and sidebars

	// Generate PDF
	tasks = append(tasks, 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
	}))

	// Run chromedp tasks
	err := chromedp.Run(allocCtx, tasks)
	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
}