package pdfprocessor

import (
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
)

// PageImage holds info about a converted page image
type PageImage struct {
	FilePath   string
	PageNumber int
	Width      int
	Height     int
}

// ConvertPDFToImages converts each page of a PDF to a PNG image using ImageMagick.
func ConvertPDFToImages(pdfPath, outputDir string, dpi int) ([]PageImage, error) {
	outputPattern := filepath.Join(outputDir, "page_%04d.png")

	cmd := exec.Command("convert",
		"-density", strconv.Itoa(dpi),
		pdfPath,
		"-depth", "8",
		"-background", "white",
		"-alpha", "remove",
		"-alpha", "off",
		outputPattern,
	)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return nil, fmt.Errorf("converting PDF to images: %w (output: %s)", err, string(output))
	}

	// ImageMagick %d starts at 0. We need 1-indexed page numbers to match pdfcpu.
	var pages []PageImage
	for i := 0; ; i++ {
		path := filepath.Join(outputDir, fmt.Sprintf("page_%04d.png", i))
		if _, err := os.Stat(path); os.IsNotExist(err) {
			break
		}
		pages = append(pages, PageImage{
			FilePath:   path,
			PageNumber: i + 1, // 1-indexed to match pdfcpu page numbering
		})
	}

	if len(pages) == 0 {
		return nil, fmt.Errorf("no pages were converted from PDF")
	}

	for i := range pages {
		if info, err := GetImageInfo(pages[i].FilePath); err == nil {
			pages[i].Width = info.Width
			pages[i].Height = info.Height
		}
	}

	return pages, nil
}

type ImageInfo struct {
	Width  int
	Height int
}

func GetImageInfo(filePath string) (ImageInfo, error) {
	cmd := exec.Command("identify", "-format", "%w %h", filePath)
	output, err := cmd.Output()
	if err != nil {
		return ImageInfo{}, err
	}
	parts := strings.Fields(string(output))
	if len(parts) < 2 {
		return ImageInfo{}, fmt.Errorf("unexpected identify output: %s", string(output))
	}
	w, _ := strconv.Atoi(parts[0])
	h, _ := strconv.Atoi(parts[1])
	return ImageInfo{Width: w, Height: h}, nil
}