package platepdf

import (
	"bytes"
	"fmt"
	"os/exec"
)

// rsvgAvailable returns true when rsvg-convert is found in PATH.
func rsvgAvailable() bool {
	_, err := exec.LookPath("rsvg-convert")
	return err == nil
}

// svgToPDFViaRsvg converts an SVG byte slice to a PDF using rsvg-convert.
// widthMM / heightMM set the output page size so the PDF is exactly that physical size.
func svgToPDFViaRsvg(svg []byte, widthMM, heightMM float64) ([]byte, error) {
	args := []string{
		"-f", "pdf",
		"--page-width", fmt.Sprintf("%.4fmm", widthMM),
		"--page-height", fmt.Sprintf("%.4fmm", heightMM),
		"-", // read from stdin
	}
	cmd := exec.Command("rsvg-convert", args...)
	cmd.Stdin = bytes.NewReader(svg)

	var stdout, stderr bytes.Buffer
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr

	err := cmd.Run()
	// rsvg-convert exits non-zero when writing to a non-terminal stdout; treat
	// a non-empty PDF output as success regardless of exit code.
	if stdout.Len() > 4 && string(stdout.Bytes()[:4]) == "%PDF" {
		return stdout.Bytes(), nil
	}
	if err != nil {
		return nil, fmt.Errorf("rsvg-convert: %w: %s", err, stderr.String())
	}
	return stdout.Bytes(), nil
}

// svgToPNGViaRsvg converts SVG to PNG at the given DPI using rsvg-convert.
func svgToPNGViaRsvg(svg []byte, dpi float64) ([]byte, error) {
	args := []string{
		"-f", "png",
		"-d", fmt.Sprintf("%.0f", dpi),
		"-p", fmt.Sprintf("%.0f", dpi),
		"-",
	}
	cmd := exec.Command("rsvg-convert", args...)
	cmd.Stdin = bytes.NewReader(svg)
	out, err := cmd.Output()
	if err != nil {
		var stderr []byte
		if ee, ok := err.(*exec.ExitError); ok {
			stderr = ee.Stderr
		}
		return nil, fmt.Errorf("rsvg-convert: %w: %s", err, stderr)
	}
	return out, nil
}