package input

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"img2pdf/internal/convert"
)

// Collect expands provided paths, walking folders to gather image files.
func Collect(inputs []string) ([]string, error) {
	var results []string
	for _, p := range inputs {
		info, err := os.Stat(p)
		if err != nil {
			return nil, fmt.Errorf("stat %s: %w", p, err)
		}
		if info.IsDir() {
			err = filepath.WalkDir(p, func(path string, d os.DirEntry, err error) error {
				if err != nil {
					return err
				}
				if d.IsDir() {
					return nil
				}
				if IsImage(path) {
					results = append(results, path)
				}
				return nil
			})
			if err != nil {
				return nil, err
			}
			continue
		}
		if IsImage(p) {
			results = append(results, p)
		}
	}
	if len(results) == 0 {
		return nil, fmt.Errorf("no supported image files found")
	}
	return results, nil
}

// IsImage returns true if the path has an image extension supported by the stdlib decoders.
func IsImage(path string) bool {
	ext := strings.ToLower(filepath.Ext(path))
	switch ext {
	case ".jpg", ".jpeg", ".png", ".gif":
		return true
	default:
		return false
	}
}

// ReadSources reads file data for conversion.
func ReadSources(paths []string) ([]convert.SourceFile, error) {
	var files []convert.SourceFile
	for _, p := range paths {
		data, err := os.ReadFile(p)
		if err != nil {
			return nil, fmt.Errorf("read %s: %w", p, err)
		}
		files = append(files, convert.SourceFile{
			Name: filepath.Base(p),
			Data: data,
		})
	}
	return files, nil
}

// DefaultOutput derives an output path based on the first input.
func DefaultOutput(first string) (string, error) {
	info, err := os.Stat(first)
	if err != nil {
		return "", fmt.Errorf("stat %s: %w", first, err)
	}
	if info.IsDir() {
		name := filepath.Base(first)
		if name == "." || name == "" {
			name = "images"
		}
		return filepath.Join(first, name+".pdf"), nil
	}
	base := strings.TrimSuffix(filepath.Base(first), filepath.Ext(first))
	if base == "" {
		base = "images"
	}
	return filepath.Join(filepath.Dir(first), base+".pdf"), nil
}