// Package rasterize converts PDF pages to in-memory images using MuPDF.
package rasterize

import (
	"fmt"
	"image"

	"github.com/gen2brain/go-fitz"
)

// DPI used when rasterizing pages for the orientation classifier.
// 150 mirrors the Ghostscript -r150 flag used in the original Python pipeline.
const DPI = 150

type Page struct {
	Index int
	Img   image.Image
}

// PDF wraps an open MuPDF document.
type PDF struct {
	doc *fitz.Document
}

func Open(data []byte) (*PDF, error) {
	doc, err := fitz.NewFromMemory(data)
	if err != nil {
		return nil, fmt.Errorf("fitz open: %w", err)
	}
	return &PDF{doc: doc}, nil
}

func (p *PDF) Close() error {
	if p == nil || p.doc == nil {
		return nil
	}
	return p.doc.Close()
}

func (p *PDF) NumPages() int {
	return p.doc.NumPage()
}

// RenderPage rasterizes a single page at the configured DPI.
func (p *PDF) RenderPage(idx int) (image.Image, error) {
	img, err := p.doc.ImageDPI(idx, DPI)
	if err != nil {
		return nil, fmt.Errorf("render page %d: %w", idx, err)
	}
	return img, nil
}