import 'dart:ffi';

import 'package:libgit2dart/libgit2dart.dart';
import 'package:libgit2dart/src/bindings/libgit2_bindings.dart';
import 'package:libgit2dart/src/bindings/patch.dart' as bindings;
import 'package:libgit2dart/src/util.dart';

class Patch {
  /// Initializes a new instance of [Patch] class from provided
  /// pointer to patch object in memory and pointers to old and new blobs/buffers.
  ///
  /// **IMPORTANT**: Should be freed to release allocated memory.
  Patch(this._patchPointer);

  /// Directly generates a patch from the difference between two blobs, buffers
  /// or blob and a buffer.
  ///
  /// [a] and [b] can be [Blob], [String] or null.
  ///
  /// [aPath] treat [a] as if it had this filename, can be null.
  ///
  /// [bPath] treat [b] as if it had this filename, can be null.
  ///
  /// [flags] is a combination of [GitDiff] flags. Defaults to [GitDiff.normal].
  ///
  /// [contextLines] is the number of unchanged lines that define the boundary
  /// of a hunk (and to display before and after). Defaults to 3.
  ///
  /// [interhunkLines] is the maximum number of unchanged lines between hunk
  /// boundaries before the hunks will be merged into one. Defaults to 0.
  ///
  /// **IMPORTANT**: Should be freed to release allocated memory.
  Patch.create({
    required Object? a,
    required Object? b,
    String? aPath,
    String? bPath,
    Set<GitDiff> flags = const {GitDiff.normal},
    int contextLines = 3,
    int interhunkLines = 0,
  }) {
    libgit2.git_libgit2_init();

    final flagsInt = flags.fold(0, (int acc, e) => acc | e.value);

    if (a is Blob?) {
      if (b is Blob?) {
        _patchPointer = bindings.fromBlobs(
          oldBlobPointer: a?.pointer ?? nullptr,
          oldAsPath: aPath,
          newBlobPointer: b?.pointer ?? nullptr,
          newAsPath: bPath,
          flags: flagsInt,
          contextLines: contextLines,
          interhunkLines: interhunkLines,
        );
      } else if (b is String?) {
        _patchPointer = bindings.fromBlobAndBuffer(
          oldBlobPointer: a?.pointer,
          oldAsPath: aPath,
          buffer: b as String?,
          bufferAsPath: bPath,
          flags: flagsInt,
          contextLines: contextLines,
          interhunkLines: interhunkLines,
        );
      } else {
        throw ArgumentError('Provided argument(s) is not Blob or String');
      }
    } else if ((a is String?) && (b is String?)) {
      _patchPointer = bindings.fromBuffers(
        oldBuffer: a as String?,
        oldAsPath: aPath,
        newBuffer: b,
        newAsPath: bPath,
        flags: flagsInt,
        contextLines: contextLines,
        interhunkLines: interhunkLines,
      );
    } else {
      throw ArgumentError('Provided argument(s) is not Blob or String');
    }
  }

  /// Creates a patch for an entry in the diff list.
  ///
  /// [diff] is the [Diff] list object.
  ///
  /// [index] is the position of an entry in diff list.
  ///
  /// **IMPORTANT**: Should be freed to release allocated memory.
  ///
  /// Throws a [LibGit2Error] if error occured.
  Patch.fromDiff({required Diff diff, required int index}) {
    libgit2.git_libgit2_init();

    _patchPointer = bindings.fromDiff(diffPointer: diff.pointer, index: index);
  }

  late final Pointer<git_patch> _patchPointer;

  /// Pointer to memory address for allocated patch object.
  Pointer<git_patch> get pointer => _patchPointer;

  /// Content of a patch as a single diff text.
  ///
  /// Throws a [LibGit2Error] if error occured.
  String get text => bindings.text(_patchPointer);

  /// Size of patch diff data in bytes.
  ///
  /// This returns the raw size of the patch data. This only includes the
  /// actual data from the lines of the diff, not the file or hunk headers.
  ///
  /// If you pass `includeContext` as true, this will be the size of all of the
  /// diff output; if you pass it as false, this will only include the actual
  /// changed lines (as if contextLines was 0).
  ///
  /// If [includeHunkHeaders] and [includeFileHeaders] are set to true, they
  /// will be included in the total size.
  int size({
    bool includeContext = false,
    bool includeHunkHeaders = false,
    bool includeFileHeaders = false,
  }) {
    return bindings.size(
      patchPointer: _patchPointer,
      includeContext: includeContext,
      includeHunkHeaders: includeHunkHeaders,
      includeFileHeaders: includeFileHeaders,
    );
  }

  /// Delta associated with a patch.
  DiffDelta get delta => DiffDelta(bindings.delta(_patchPointer));

  /// List of hunks in a patch.
  List<DiffHunk> get hunks {
    final length = bindings.numHunks(_patchPointer);
    final hunks = <DiffHunk>[];

    for (var i = 0; i < length; i++) {
      final hunk = bindings.hunk(patchPointer: _patchPointer, hunkIndex: i);
      hunks.add(
        DiffHunk(
          _patchPointer,
          hunk['hunk']! as Pointer<git_diff_hunk>,
          hunk['linesN']! as int,
          i,
        ),
      );
    }

    return hunks;
  }

  /// Releases memory allocated for patch object.
  void free() => bindings.free(_patchPointer);

  @override
  String toString() => 'Patch{size: ${size()}, delta: $delta}';
}