package files

import (
	"bytes"
	"net/http"
	"path/filepath"
	"strings"
)

type PreviewResult struct {
	Type    string `json:"type"`
	Content string `json:"content,omitempty"`
	Mime    string `json:"mime"`
	Size    int64  `json:"size"`
}

var textMimes = map[string]bool{
	"text/plain":                          true,
	"text/html":                           true,
	"text/css":                            true,
	"text/javascript":                     true,
	"application/json":                    true,
	"application/xml":                     true,
	"application/xhtml+xml":               true,
	"application/javascript":              true,
}

var imageMimes = map[string]bool{
	"image/png":  true,
	"image/jpeg": true,
	"image/gif":  true,
	"image/webp": true,
	"image/svg+xml": true,
	"image/bmp":  true,
	"image/tiff": true,
}

func Preview(path string, max int64, allowedRoots []string) (*PreviewResult, error) {
	data, err := ReadFile(path, max, allowedRoots)
	if err != nil {
		return nil, err
	}

	mime := http.DetectContentType(data)
	size := int64(len(data))

	trimmed := bytes.TrimSpace(data)
	if len(trimmed) > 0 {
		mime = http.DetectContentType(trimmed)
	}

	result := &PreviewResult{
		Mime: mime,
		Size: size,
	}

	if imageMimes[mime] || strings.HasPrefix(mime, "image/") {
		result.Type = "image"
		return result, nil
	}

	if textMimes[mime] || strings.HasPrefix(mime, "text/") || isLikelyText(trimmed) {
		result.Type = "text"
		if size > 0 {
			result.Content = string(data)
			if int64(len(result.Content)) > max {
				result.Content = result.Content[:max]
			}
		}
		return result, nil
	}

	result.Type = "binary"
	return result, nil
}

func isLikelyText(data []byte) bool {
	if len(data) == 0 {
		return false
	}
	nulls := 0
	for _, b := range data {
		gb := int(b)
		if (gb < 32 && gb != 9 && gb != 10 && gb != 13) || gb == 127 {
			nulls++
		}
	}
	return float64(nulls)/float64(len(data)) < 0.1
}

func ExtensionIcon(name string) string {
	ext := strings.ToLower(filepath.Ext(name))
	switch ext {
	case ".png", ".jpg", ".jpeg", ".gif", ".webp", ".svg", ".bmp", ".ico":
		return "image"
	case ".mp4", ".avi", ".mkv", ".mov", ".wmv", ".flv", ".webm":
		return "video"
	case ".mp3", ".wav", ".ogg", ".flac", ".aac", ".wma":
		return "audio"
	case ".zip", ".tar", ".gz", ".bz2", ".xz", ".rar", ".7z":
		return "archive"
	case ".pdf":
		return "pdf"
	case ".doc", ".docx", ".odt", ".rtf":
		return "word"
	case ".xls", ".xlsx", ".csv", ".ods":
		return "spreadsheet"
	case ".txt", ".md", ".log", ".cfg", ".conf", ".ini", ".yaml", ".yml", ".toml", ".json", ".xml":
		return "text"
	default:
		return "file"
	}
}