package parse

import (
	"bufio"
	"bytes"
	"fmt"
	"io"

	"git.sr.ht/~rjarry/aerc/lib/log"
)

// ExtractImages scans a reader for OSC 9 image markers, replaces them with
// null-byte-delimited placeholders (\x00IMG:N\x00), and returns the cleaned
// reader plus a slice of ImageRef structs.
//
// Lines containing valid image markers are replaced entirely with the
// placeholder. Lines with invalid markers (e.g. missing path) pass through
// unchanged.
func ExtractImages(r io.Reader) (io.Reader, []ImageRef) {
	var images []ImageRef
	buf := bytes.NewBuffer(nil)
	scanner := bufio.NewScanner(r)
	scanner.Buffer(nil, 1024*1024*1024)
	for scanner.Scan() {
		line := scanner.Bytes()
		if bytes.Contains(line, oscImagePrefix) {
			if ref, ok := ParseImageOSC(line); ok {
				ref.Index = len(images)
				images = append(images, *ref)
				fmt.Fprintf(buf, "\x00IMG:%d\x00\n", ref.Index)
				continue
			}
		}
		buf.Write(line)
		buf.WriteByte('\n')
	}
	if err := scanner.Err(); err != nil {
		log.Warnf("ExtractImages: scan error: %v", err)
	}
	return buf, images
}

// ReplacePlaceholders converts \x00IMG:N\x00 placeholders into human-readable
// [image: alt] text suitable for display in a pager.
func ReplacePlaceholders(data []byte, images []ImageRef) []byte {
	result := bytes.NewBuffer(nil)
	for _, line := range bytes.Split(data, []byte("\n")) {
		trimmed := bytes.TrimSpace(line)
		if len(trimmed) > 6 && trimmed[0] == 0 &&
			bytes.HasPrefix(trimmed, []byte("\x00IMG:")) &&
			trimmed[len(trimmed)-1] == 0 {
			// Extract index
			numStr := string(trimmed[5 : len(trimmed)-1])
			idx := 0
			for _, c := range numStr {
				if c >= '0' && c <= '9' {
					idx = idx*10 + int(c-'0')
				}
			}
			if idx < len(images) && images[idx].Alt != "" {
				fmt.Fprintf(result, "[image: %s]\n", images[idx].Alt)
			} else {
				result.WriteString("[image]\n")
			}
		} else {
			result.Write(line)
			result.WriteByte('\n')
		}
	}
	return result.Bytes()
}