diff2html/src/line-by-line-renderer.ts

import HoganJsUtils from "./hoganjs-utils";
import * as Rematch from "./rematch";
import * as renderUtils from "./render-utils";
import {
  DiffFile,
  DiffLine,
  LineType,
  DiffBlock,
  DiffLineDeleted,
  DiffLineContent,
  DiffLineContext,
  DiffLineInserted
} from "./types";

export interface LineByLineRendererConfig extends renderUtils.RenderConfig {
  renderNothingWhenEmpty?: boolean;
  matchingMaxComparisons?: number;
  maxLineSizeInBlockForComparison?: number;
}

export const defaultLineByLineRendererConfig = {
  ...renderUtils.defaultRenderConfig,
  renderNothingWhenEmpty: false,
  matchingMaxComparisons: 2500,
  maxLineSizeInBlockForComparison: 200
};

const genericTemplatesPath = "generic";
const baseTemplatesPath = "line-by-line";
const iconsBaseTemplatesPath = "icon";
const tagsBaseTemplatesPath = "tag";

export default class LineByLineRenderer {
  private readonly hoganUtils: HoganJsUtils;
  private readonly config: typeof defaultLineByLineRendererConfig;

  constructor(hoganUtils: HoganJsUtils, config: LineByLineRendererConfig = {}) {
    this.hoganUtils = hoganUtils;
    this.config = { ...defaultLineByLineRendererConfig, ...config };
  }

  render(diffFiles: DiffFile[]): string {
    const diffsHtml = diffFiles
      .map(file => {
        let diffs;
        if (file.blocks.length) {
          diffs = this.generateFileHtml(file);
        } else {
          diffs = this.generateEmptyDiff();
        }
        return this.makeFileDiffHtml(file, diffs);
      })
      .join("\n");

    return this.hoganUtils.render(genericTemplatesPath, "wrapper", { content: diffsHtml });
  }

  makeFileDiffHtml(file: DiffFile, diffs: string): string {
    if (this.config.renderNothingWhenEmpty && Array.isArray(file.blocks) && file.blocks.length === 0) return "";

    const fileDiffTemplate = this.hoganUtils.template(baseTemplatesPath, "file-diff");
    const filePathTemplate = this.hoganUtils.template(genericTemplatesPath, "file-path");
    const fileIconTemplate = this.hoganUtils.template(iconsBaseTemplatesPath, "file");
    const fileTagTemplate = this.hoganUtils.template(tagsBaseTemplatesPath, renderUtils.getFileIcon(file));

    return fileDiffTemplate.render({
      file: file,
      fileHtmlId: renderUtils.getHtmlId(file),
      diffs: diffs,
      filePath: filePathTemplate.render(
        {
          fileDiffName: renderUtils.filenameDiff(file)
        },
        {
          fileIcon: fileIconTemplate,
          fileTag: fileTagTemplate
        }
      )
    });
  }

  generateEmptyDiff(): string {
    return this.hoganUtils.render(genericTemplatesPath, "empty-diff", {
      contentClass: "d2h-code-line",
      CSSLineClass: renderUtils.CSSLineClass
    });
  }

  generateFileHtml(file: DiffFile): string {
    const matcher = Rematch.newMatcherFn(
      Rematch.newDistanceFn((e: DiffLine) => renderUtils.deconstructLine(e.content, file.isCombined).content)
    );

    return file.blocks
      .map(block => {
        let lines = this.hoganUtils.render(genericTemplatesPath, "block-header", {
          CSSLineClass: renderUtils.CSSLineClass,
          blockHeader: block.header,
          lineClass: "d2h-code-linenumber",
          contentClass: "d2h-code-line"
        });

        this.applyLineGroupping(block).forEach(([contextLines, oldLines, newLines]) => {
          if (oldLines.length && newLines.length && !contextLines.length) {
            this.applyRematchMatching(oldLines, newLines, matcher).map(([oldLines, newLines]) => {
              const { left, right } = this.processChangedLines(file.isCombined, oldLines, newLines);
              lines += left;
              lines += right;
            });
          } else if (contextLines.length) {
            contextLines.forEach(line => {
              const { prefix, content } = renderUtils.deconstructLine(line.content, file.isCombined);
              lines += this.generateSingleLineHtml({
                type: renderUtils.CSSLineClass.CONTEXT,
                prefix: prefix,
                content: content,
                oldNumber: line.oldNumber,
                newNumber: line.newNumber
              });
            });
          } else if (oldLines.length || newLines.length) {
            const { left, right } = this.processChangedLines(file.isCombined, oldLines, newLines);
            lines += left;
            lines += right;
          } else {
            console.error("Unknown state reached while processing groups of lines", contextLines, oldLines, newLines);
          }
        });

        return lines;
      })
      .join("\n");
  }

  applyLineGroupping(block: DiffBlock): DiffLineGroups {
    const blockLinesGroups: DiffLineGroups = [];

    let oldLines: (DiffLineDeleted & DiffLineContent)[] = [];
    let newLines: (DiffLineInserted & DiffLineContent)[] = [];

    for (let i = 0; i < block.lines.length; i++) {
      const diffLine = block.lines[i];

      if (
        (diffLine.type !== LineType.INSERT && newLines.length) ||
        (diffLine.type === LineType.CONTEXT && oldLines.length > 0)
      ) {
        blockLinesGroups.push([[], oldLines, newLines]);
        oldLines = [];
        newLines = [];
      }

      if (diffLine.type === LineType.CONTEXT) {
        blockLinesGroups.push([[diffLine], [], []]);
      } else if (diffLine.type === LineType.INSERT && oldLines.length === 0) {
        blockLinesGroups.push([[], [], [diffLine]]);
      } else if (diffLine.type === LineType.INSERT && oldLines.length > 0) {
        newLines.push(diffLine);
      } else if (diffLine.type === LineType.DELETE) {
        oldLines.push(diffLine);
      }
    }

    if (oldLines.length || newLines.length) {
      blockLinesGroups.push([[], oldLines, newLines]);
      oldLines = [];
      newLines = [];
    }

    return blockLinesGroups;
  }

  applyRematchMatching(
    oldLines: DiffLine[],
    newLines: DiffLine[],
    matcher: Rematch.MatcherFn<DiffLine>
  ): DiffLine[][][] {
    const comparisons = oldLines.length * newLines.length;
    const maxLineSizeInBlock = Math.max.apply(
      null,
      [0].concat(oldLines.concat(newLines).map(elem => elem.content.length))
    );
    const doMatching =
      comparisons < this.config.matchingMaxComparisons &&
      maxLineSizeInBlock < this.config.maxLineSizeInBlockForComparison &&
      (this.config.matching === "lines" || this.config.matching === "words");

    const matches = doMatching ? matcher(oldLines, newLines) : [[oldLines, newLines]];

    return matches;
  }

  processChangedLines(isCombined: boolean, oldLines: DiffLine[], newLines: DiffLine[]): FileHtml {
    const fileHtml = {
      right: "",
      left: ""
    };

    const maxLinesNumber = Math.max(oldLines.length, newLines.length);
    for (let i = 0; i < maxLinesNumber; i++) {
      const oldLine = oldLines[i];
      const newLine = newLines[i];

      const diff =
        oldLine !== undefined && newLine !== undefined
          ? renderUtils.diffHighlight(oldLine.content, newLine.content, isCombined, this.config)
          : undefined;

      const preparedOldLine =
        oldLine !== undefined && oldLine.oldNumber !== undefined
          ? {
              ...(diff !== undefined
                ? {
                    prefix: diff.oldLine.prefix,
                    content: diff.oldLine.content,
                    type: renderUtils.CSSLineClass.DELETE_CHANGES
                  }
                : {
                    ...renderUtils.deconstructLine(oldLine.content, isCombined),
                    type: renderUtils.toCSSClass(oldLine.type)
                  }),
              oldNumber: oldLine.oldNumber,
              newNumber: oldLine.newNumber
            }
          : undefined;

      const preparedNewLine =
        newLine !== undefined && newLine.newNumber !== undefined
          ? {
              ...(diff !== undefined
                ? {
                    prefix: diff.newLine.prefix,
                    content: diff.newLine.content,
                    type: renderUtils.CSSLineClass.INSERT_CHANGES
                  }
                : {
                    ...renderUtils.deconstructLine(newLine.content, isCombined),
                    type: renderUtils.toCSSClass(newLine.type)
                  }),
              oldNumber: newLine.oldNumber,
              newNumber: newLine.newNumber
            }
          : undefined;

      const { left, right } = this.generateLineHtml(preparedOldLine, preparedNewLine);
      fileHtml.left += left;
      fileHtml.right += right;
    }

    return fileHtml;
  }

  generateLineHtml(oldLine?: DiffPreparedLine, newLine?: DiffPreparedLine): FileHtml {
    return {
      left: this.generateSingleLineHtml(oldLine),
      right: this.generateSingleLineHtml(newLine)
    };
  }

  generateSingleLineHtml(line?: DiffPreparedLine): string {
    if (line === undefined) return "";

    const lineNumberHtml = this.hoganUtils.render(baseTemplatesPath, "numbers", {
      oldNumber: line.oldNumber || "",
      newNumber: line.newNumber || ""
    });

    return this.hoganUtils.render(genericTemplatesPath, "line", {
      type: line.type,
      lineClass: "d2h-code-linenumber",
      contentClass: "d2h-code-line",
      prefix: line.prefix === " " ? "&nbsp;" : line.prefix,
      content: line.content,
      lineNumber: lineNumberHtml
    });
  }
}

type DiffLineGroups = [
  (DiffLineContext & DiffLineContent)[],
  (DiffLineDeleted & DiffLineContent)[],
  (DiffLineInserted & DiffLineContent)[]
][];

type DiffPreparedLine = {
  type: renderUtils.CSSLineClass;
  prefix: string;
  content: string;
  oldNumber?: number;
  newNumber?: number;
};

type FileHtml = {
  left: string;
  right: string;
};