using System;

namespace GitConverter.Lib.Models
{
    /// <summary>
    /// Helper methods for working with <see cref="FileExtension"/>.
    /// </summary>
    /// <remarks>
    /// Responsibilities
    /// - Provide the canonical dot-prefixed filename extension for a given <see cref="FileExtension"/>
    ///   via <see cref="ToDotExtension(FileExtension)"/>.
    /// - Resolve common user-facing converter option strings to <see cref="FileExtension"/> values
    ///   via <see cref="FromOption(string)"/> (case-insensitive).
    ///
    /// Recommended usage pattern (converters & callers)
    /// 1. Map the requested target option to the enum:
    ///      var fe = FileExtensionHelpers.FromOption(optionString);
    /// 2. Obtain the suffix:
    ///      var suffix = fe.HasValue ? fe.Value.ToDotExtension() : FileExtension.Csv.ToDotExtension();
    /// 3. Compose a deterministic output filename:
    ///      var outPath = Path.Combine(outputFolder, $"output_{timestamp}{suffix}");
    ///
    /// Why this pattern
    /// - It centralizes filename-suffix decisions so changing a canonical extension (for example
    ///   switching FileGdb to use ".gdb") only needs one code change.
    /// - It reduces accidental inconsistencies and makes tests and documentation easier to keep in sync.
    ///
    /// Behavior & guarantees
    /// - The mapping implemented by <see cref="ToDotExtension(FileExtension)"/> is the single source
    ///   of truth for file suffixes used by converters when composing output file names.
    /// - Helpers are pure, stateless and thread-safe.
    ///
    /// Testing guidance
    /// - Add unit tests that assert:
    ///   - Each enum member returns the expected dot-prefixed extension from <see cref="ToDotExtension(FileExtension)"/>.
    ///   - <see cref="FromOption(string)"/> recognizes common option strings case-insensitively and returns null for unknown strings.
    /// </remarks>
    public static class FileExtensionHelpers
    {
        public static string ToDotExtension(this FileExtension ext)
        {
            switch (ext)
            {
                case FileExtension.Csv: return ".csv";
                case FileExtension.EsriJson: return ".json";
                case FileExtension.FileGdb: return ".gdb";
                case FileExtension.GeoJson: return ".json";
                case FileExtension.GeoJsonSeq: return ".json";
                case FileExtension.GeoPackage: return ".gpkg";
                case FileExtension.Gml: return ".gml";
                case FileExtension.Gpx: return ".gpx";
                case FileExtension.Kml: return ".kml";
                case FileExtension.Kmz: return ".kmz";
                case FileExtension.MapInfoInterchange: return ".mif";
                case FileExtension.MapInfoTab: return ".tab";
                case FileExtension.Osm: return ".osm";
                case FileExtension.Shapefile: return ".shp";
                case FileExtension.TopoJson: return ".json";
                default: return string.Empty;
            }
        }

        public static FileExtension? FromOption(string option)
        {
            if (string.IsNullOrWhiteSpace(option)) return null;

            switch (option.Trim().ToLowerInvariant())
            {
                case "csv": return FileExtension.Csv;
                case "esrijson": return FileExtension.EsriJson;
                case "gdb":
                case "gdbtable":
                case "gdbtablx":
                    return FileExtension.FileGdb;
                case "geojson": return FileExtension.GeoJson;
                case "jsonl":
                case "ndjson":
                    return FileExtension.GeoJsonSeq;
                case "gpkg": return FileExtension.GeoPackage;
                case "gml": return FileExtension.Gml;
                case "gpx": return FileExtension.Gpx;
                case "kml": return FileExtension.Kml;
                case "kmz": return FileExtension.Kmz;
                case "mif":
                case "mid": return FileExtension.MapInfoInterchange;
                case "tab":
                case "dat":
                case "map":
                case "id":
                    return FileExtension.MapInfoTab;
                case "osm": return FileExtension.Osm;
                case "shp":
                case "shx":
                case "dbf":
                    return FileExtension.Shapefile;
                case "topojson": return FileExtension.TopoJson;
                 
                default: return null;
            }
        }
    }
}