package cv

import (
	"bytes"
	"context"
	"database/sql"
	"embed"
	"errors"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"github.com/cobr-ai/apex/internal/eval"
)

//go:embed prompts/tailor.md templates/cv-template.html
var embeddedFS embed.FS

// CVResult holds the generated file paths.
type CVResult struct {
	HTMLPath string
	PDFPath  string
}

// HTMLExporter generates a tailored HTML CV + PDF via Chromium.
type HTMLExporter struct {
	DB        *sql.DB
	CVPath    string // path to cv.md (defaults to ~/.apex/cv.md)
	OutputDir string // defaults to ~/.apex/cv/
}


// Generate creates a tailored HTML CV (and optionally PDF) for the given job URL.
// Flow: query DB for JD → read cv.md → load profile → read tailor prompt →
// call Claude → render HTML → call Chromium for PDF.
func (e *HTMLExporter) Generate(ctx context.Context, jobURL string) (CVResult, error) {
	cvPath := e.CVPath
	if cvPath == "" {
		home, err := os.UserHomeDir()
		if err != nil {
			return CVResult{}, fmt.Errorf("expand home: %w", err)
		}
		cvPath = filepath.Join(home, ".apex", "cv.md")
	}

	outputDir := e.OutputDir
	if outputDir == "" {
		home, err := os.UserHomeDir()
		if err != nil {
			return CVResult{}, fmt.Errorf("expand home: %w", err)
		}
		outputDir = filepath.Join(home, ".apex", "cv")
	}

	// Ensure output directory exists
	if err := os.MkdirAll(outputDir, 0700); err != nil {
		return CVResult{}, fmt.Errorf("mkdir %s: %w", outputDir, err)
	}

	// Query jobs table for company, title, description by URL
	var company, title, description string
	err := e.DB.QueryRowContext(ctx, `
		SELECT company, title, COALESCE(description, '')
		FROM jobs
		WHERE url = ?
		LIMIT 1
	`, jobURL).Scan(&company, &title, &description)
	if err != nil {
		if err == sql.ErrNoRows {
			return CVResult{}, fmt.Errorf("job not found: %s", jobURL)
		}
		return CVResult{}, fmt.Errorf("query job: %w", err)
	}

	// Read cv.md
	cvContent, err := os.ReadFile(cvPath)
	if err != nil {
		return CVResult{}, fmt.Errorf("read cv.md: %w", err)
	}

	// Load profile from DB
	var name, email, location string
	err = e.DB.QueryRowContext(ctx, `
		SELECT name, email, location FROM profile LIMIT 1
	`).Scan(&name, &email, &location)
	if err != nil && err != sql.ErrNoRows {
		return CVResult{}, fmt.Errorf("query profile: %w", err)
	}

	// Read tailor.md prompt template
	promptTpl, err := embeddedFS.ReadFile("prompts/tailor.md")
	if err != nil {
		return CVResult{}, fmt.Errorf("read tailor prompt: %w", err)
	}

	// Substitute placeholders in prompt
	prompt := strings.NewReplacer(
		"{{CV}}", string(cvContent),
		"{{JD}}", description,
		"{{NAME}}", name,
		"{{EMAIL}}", email,
		"{{LOCATION}}", location,
	).Replace(string(promptTpl))

	// Call Claude CLI to generate tailored CV HTML
	html, err := e.callClaude(ctx, prompt)
	if err != nil {
		return CVResult{}, fmt.Errorf("call claude: %w", err)
	}

	// Generate filenames
	now := time.Now().Format("2006-01-02")
	companySlug := eval.Slugify(company)
	nameSlug := eval.Slugify(name)
	baseFilename := fmt.Sprintf("cv-%s-%s-%s", nameSlug, companySlug, now)

	htmlPath := filepath.Join(outputDir, baseFilename+".html")
	pdfPath := filepath.Join(outputDir, baseFilename+".pdf")

	// Write HTML file
	if err := os.WriteFile(htmlPath, []byte(html), 0600); err != nil {
		return CVResult{}, fmt.Errorf("write html: %w", err)
	}

	// Generate PDF via Chromium if available
	if err := e.generatePDF(htmlPath, pdfPath); err != nil {
		// PDF generation is best-effort; don't fail the entire operation
		fmt.Fprintf(os.Stderr, "pdf generation failed (continuing with HTML only): %v\n", err)
	}

	return CVResult{
		HTMLPath: htmlPath,
		PDFPath:  pdfPath,
	}, nil
}

// callClaude runs the Claude CLI with the given prompt and returns raw HTML output.
// Timeout: 10 minutes for full document generation.
func (e *HTMLExporter) callClaude(ctx context.Context, prompt string) (string, error) {
	timeoutCtx, cancel := context.WithTimeout(ctx, 10*time.Minute)
	defer cancel()

	cmd := exec.CommandContext(timeoutCtx, "claude", "--print", "--output-format", "text")

	stdin, err := cmd.StdinPipe()
	if err != nil {
		return "", fmt.Errorf("stdin pipe: %w", err)
	}

	stdout, err := cmd.StdoutPipe()
	if err != nil {
		return "", fmt.Errorf("stdout pipe: %w", err)
	}

	var stderr bytes.Buffer
	cmd.Stderr = &stderr

	if err := cmd.Start(); err != nil {
		return "", fmt.Errorf("start claude: %w", err)
	}

	// Feed prompt via stdin in a goroutine
	go func() {
		defer stdin.Close()
		_, _ = io.WriteString(stdin, prompt)
	}()

	// Read output
	output, err := io.ReadAll(stdout)
	if err != nil {
		return "", fmt.Errorf("read stdout: %w", err)
	}

	if err := cmd.Wait(); err != nil {
		if timeoutCtx.Err() == context.DeadlineExceeded {
			return "", errors.New("claude timeout (10 minutes)")
		}
		return "", fmt.Errorf("claude exit: %w (stderr: %s)", err, stderr.String())
	}

	html := string(output)
	if strings.TrimSpace(html) == "" {
		return "", errors.New("claude returned empty output")
	}

	return html, nil
}

// generatePDF uses Chromium to convert HTML to PDF.
// Returns early if chromium not found; it's optional.
func (e *HTMLExporter) generatePDF(htmlPath, pdfPath string) error {
	// Resolve symlinks on the output directory (file doesn't exist yet so we
	// can only canonicalize the dir). This prevents symlink traversal bypasses
	// that filepath.Clean alone would miss.
	realDir, err := filepath.EvalSymlinks(filepath.Dir(htmlPath))
	if err != nil {
		realDir = filepath.Clean(filepath.Dir(htmlPath))
	}
	absPDF := filepath.Clean(pdfPath)
	if !strings.HasPrefix(absPDF, realDir+string(os.PathSeparator)) {
		return fmt.Errorf("pdf path escapes output directory")
	}

	chromiumPath := "/usr/bin/chromium"
	if _, err := os.Stat(chromiumPath); err != nil {
		return fmt.Errorf("chromium not found at %s", chromiumPath)
	}

	// Convert to absolute path if needed
	absHTMLPath, err := filepath.Abs(htmlPath)
	if err != nil {
		absHTMLPath = htmlPath
	}

	// Chromium needs file:// URL
	fileURL := "file://" + absHTMLPath

	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	cmd := exec.CommandContext(ctx,
		chromiumPath,
		"--headless=new",
		"--disable-gpu",
		"--no-sandbox",
		fmt.Sprintf("--print-to-pdf=%s", pdfPath),
		fileURL,
	)

	var stderr bytes.Buffer
	cmd.Stderr = &stderr

	if err := cmd.Run(); err != nil {
		return fmt.Errorf("chromium: %w (stderr: %s)", err, stderr.String())
	}

	return nil
}