import 'dart:ffi';

import 'package:ffi/ffi.dart';
import 'package:libgit2dart/src/bindings/libgit2_bindings.dart';
import 'package:libgit2dart/src/error.dart';
import 'package:libgit2dart/src/util.dart';

/// Initializes a rebase operation to rebase the changes in [branchPointer]
/// relative to [upstreamPointer] onto [ontoPointer] another branch. To begin
/// the rebase process, call [next]. The returned rebase must be freed with
/// [free].
///
/// [branchPointer] is the terminal commit to rebase, or null to rebase the
/// current branch.
///
/// [upstreamPointer] is the commit to begin rebasing from, or null to rebase
/// all reachable commits.
///
/// [ontoPointer] is the branch to rebase onto, or null to rebase onto the
/// given upstream.
///
/// Throws a [LibGit2Error] if error occured.
Pointer<git_rebase> init({
  required Pointer<git_repository> repoPointer,
  required Pointer<git_annotated_commit>? branchPointer,
  required Pointer<git_annotated_commit>? upstreamPointer,
  required Pointer<git_annotated_commit>? ontoPointer,
}) {
  final out = calloc<Pointer<git_rebase>>();
  final opts = calloc<git_rebase_options>();

  libgit2.git_rebase_options_init(opts, GIT_REBASE_OPTIONS_VERSION);

  final error = libgit2.git_rebase_init(
    out,
    repoPointer,
    branchPointer ?? nullptr,
    upstreamPointer ?? nullptr,
    ontoPointer ?? nullptr,
    opts,
  );

  final result = out.value;

  calloc.free(out);
  calloc.free(opts);

  if (error < 0) {
    throw LibGit2Error(libgit2.git_error_last());
  } else {
    return result;
  }
}

/// Opens an existing rebase that was previously started by either an
/// invocation of [init] or by another client. The returned rebase must be
/// freed with [free].
///
/// Throws a [LibGit2Error] if error occured.
Pointer<git_rebase> open(Pointer<git_repository> repo) {
  final out = calloc<Pointer<git_rebase>>();
  final opts = calloc<git_rebase_options>();
  libgit2.git_rebase_options_init(opts, GIT_REBASE_OPTIONS_VERSION);

  final error = libgit2.git_rebase_open(out, repo, opts);

  final result = out.value;

  calloc.free(out);

  if (error < 0) {
    throw LibGit2Error(libgit2.git_error_last());
  } else {
    return result;
  }
}

/// Gets the count of rebase operations that are to be applied.
int operationsCount(Pointer<git_rebase> rebase) {
  return libgit2.git_rebase_operation_entrycount(rebase);
}

/// Gets the rebase operation specified by the given index.
Pointer<git_rebase_operation> getOperationByIndex({
  required Pointer<git_rebase> rebase,
  required int index,
}) {
  return libgit2.git_rebase_operation_byindex(rebase, index);
}

/// Gets the index of the rebase operation that is currently being applied. If
/// the first operation has not yet been applied (because you have called [init]
/// but not yet [next]) then this returns `-1`.
int currentOperation(Pointer<git_rebase> rebase) {
  return libgit2.git_rebase_operation_current(rebase);
}

/// Performs the next rebase operation and returns the information about it.
/// If the operation is one that applies a patch (which is any operation except
/// GIT_REBASE_OPERATION_EXEC) then the patch will be applied and the index and
/// working directory will be updated with the changes. If there are conflicts,
/// you will need to address those before committing the changes.
///
/// Throws a [LibGit2Error] if error occured.
Pointer<git_rebase_operation> next(Pointer<git_rebase> rebase) {
  final out = calloc<Pointer<git_rebase_operation>>();
  final error = libgit2.git_rebase_next(out, rebase);

  final result = out.value;

  calloc.free(out);

  if (error < 0) {
    throw LibGit2Error(libgit2.git_error_last());
  } else {
    return result;
  }
}

/// Commits the current patch. You must have resolved any conflicts that were
/// introduced during the patch application from the [next] invocation.
///
/// Throws a [LibGit2Error] if error occured.
void commit({
  required Pointer<git_rebase> rebasePointer,
  required Pointer<git_signature>? authorPointer,
  required Pointer<git_signature> committerPointer,
  required String? message,
}) {
  final out = calloc<git_oid>();
  final messageC = message?.toNativeUtf8().cast<Char>() ?? nullptr;

  final error = libgit2.git_rebase_commit(
    out,
    rebasePointer,
    authorPointer ?? nullptr,
    committerPointer,
    nullptr,
    messageC,
  );

  calloc.free(out);
  calloc.free(messageC);

  if (error < 0) {
    throw LibGit2Error(libgit2.git_error_last());
  }
}

/// Finishes a rebase that is currently in progress once all patches have been
/// applied.
void finish(Pointer<git_rebase> rebase) =>
    libgit2.git_rebase_finish(rebase, nullptr);

/// Aborts a rebase that is currently in progress, resetting the repository and
/// working directory to their state before rebase began.
void abort(Pointer<git_rebase> rebase) => libgit2.git_rebase_abort(rebase);

/// Gets the original HEAD id for merge rebases.
Pointer<git_oid> origHeadOid(Pointer<git_rebase> rebase) =>
    libgit2.git_rebase_orig_head_id(rebase);

/// Gets the original HEAD ref name for merge rebases.
String origHeadName(Pointer<git_rebase> rebase) {
  final result = libgit2.git_rebase_orig_head_name(rebase);
  return result == nullptr ? '' : result.cast<Utf8>().toDartString();
}

/// Gets the onto id for merge rebases.
Pointer<git_oid> ontoOid(Pointer<git_rebase> rebase) =>
    libgit2.git_rebase_onto_id(rebase);

/// Gets the onto ref name for merge rebases.
String ontoName(Pointer<git_rebase> rebase) {
  return libgit2.git_rebase_onto_name(rebase).cast<Utf8>().toDartString();
}

/// Free memory allocated for rebase object.
void free(Pointer<git_rebase> rebase) => libgit2.git_rebase_free(rebase);