import type { DiffLine } from "./diff-line";

export enum DiffHunkExpansionType {
  /** The hunk header cannot be expanded at all. */
  None = "None",

  /**
   * The hunk header can be expanded up exclusively. Only the first hunk can be
   * expanded up exclusively.
   */
  Up = "Up",

  /**
   * The hunk header can be expanded down exclusively. Only the last hunk (if
   * it's the dummy hunk with only one line) can be expanded down exclusively.
   */
  Down = "Down",

  /** The hunk header can be expanded both up and down. */
  Both = "Both",

  /**
   * The hunk header represents a short gap that, when expanded, will
   * result in merging this hunk and the hunk above.
   */
  Short = "Short",
}

/** each diff is made up of a number of hunks */
export class DiffHunk {
  /**
   * @param header The details from the diff hunk header about the line start and patch length.
   * @param lines The contents - context and changes - of the diff section.
   * @param unifiedDiffStart The diff hunk's start position in the overall file diff.
   * @param unifiedDiffEnd The diff hunk's end position in the overall file diff.
   */
  public constructor(
    public readonly header: DiffHunkHeader,
    public readonly lines: ReadonlyArray<DiffLine>,
    public readonly unifiedDiffStart: number,
    public readonly unifiedDiffEnd: number,
    public readonly expansionType: DiffHunkExpansionType
  ) {}

  public equals(other: DiffHunk) {
    if (this === other) {
      return true;
    }

    return (
      this.header.equals(other.header) &&
      this.unifiedDiffStart === other.unifiedDiffStart &&
      this.unifiedDiffEnd === other.unifiedDiffEnd &&
      this.expansionType === other.expansionType &&
      this.lines.length === other.lines.length &&
      this.lines.every((xLine, ix) => xLine.equals(other.lines[ix]))
    );
  }
}

/** details about the start and end of a diff hunk */
export class DiffHunkHeader {
  /**
   * @param oldStartLine The line in the old (or original) file where this diff hunk starts.
   * @param oldLineCount The number of lines in the old (or original) file that this diff hunk covers
   * @param newStartLine The line in the new file where this diff hunk starts.
   * @param newLineCount The number of lines in the new file that this diff hunk covers.
   */
  public constructor(
    public readonly oldStartLine: number,
    public readonly oldLineCount: number,
    public readonly newStartLine: number,
    public readonly newLineCount: number
  ) {}

  public toDiffLineRepresentation() {
    return `@@ -${this.oldStartLine},${this.oldLineCount} +${this.newStartLine},${this.newLineCount} @@`;
  }

  public equals(other: DiffHunkHeader) {
    return (
      this.oldStartLine === other.oldStartLine &&
      this.oldLineCount === other.oldLineCount &&
      this.newStartLine === other.newStartLine &&
      this.oldStartLine === other.oldStartLine
    );
  }
}

/** the contents of a diff generated by Git */
export interface IRawDiff {
  /**
   * The plain text contents of the diff header. This contains
   * everything from the start of the diff up until the first
   * hunk header starts. Note that this does not include a trailing
   * newline.
   */
  readonly header: string;

  /**
   * The plain text contents of the diff. This contains everything
   * after the diff header until the last character in the diff.
   *
   * Note that this does not include a trailing newline nor does
   * it include diff 'no newline at end of file' comments. For
   * no-newline information, consult the DiffLine noTrailingNewLine
   * property.
   */
  readonly contents: string;

  /**
   * Each hunk in the diff with information about start, and end
   * positions, lines and line statuses.
   */
  readonly hunks: ReadonlyArray<DiffHunk>;

  /**
   * Whether or not the unified diff indicates that the contents
   * could not be diffed due to one of the versions being binary.
   */
  readonly isBinary: boolean;

  /** The largest line number in the diff */
  readonly maxLineNumber: number;

  /** Whether or not the diff has invisible bidi characters */
  readonly hasHiddenBidiChars: boolean;
}