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/**
* @license
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners';
import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin';
import {PolymerElement} from '@polymer/polymer/polymer-element';
import {
GrDiffLine,
GrDiffLineType,
FILE,
Highlights,
} from '../gr-diff/gr-diff-line';
import {
GrDiffGroup,
GrDiffGroupType,
hideInContextControl,
} from '../gr-diff/gr-diff-group';
import {CancelablePromise, util} from '../../../scripts/util';
import {customElement, property} from '@polymer/decorators';
import {DiffContent} from '../../../types/diff';
import {Side} from '../../../constants/constants';
const WHOLE_FILE = -1;
interface State {
lineNums: {
left: number;
right: number;
};
chunkIndex: number;
}
interface ChunkEnd {
offset: number;
keyLocation: boolean;
}
export interface KeyLocations {
left: {[key: string]: boolean};
right: {[key: string]: boolean};
}
/**
* The maximum size for an addition or removal chunk before it is broken down
* into a series of chunks that are this size at most.
*
* Note: The value of 120 is chosen so that it is larger than the default
* _asyncThreshold of 64, but feel free to tune this constant to your
* performance needs.
*/
const MAX_GROUP_SIZE = 120;
/**
* Converts the API's `DiffContent`s to `GrDiffGroup`s for rendering.
*
* Glossary:
* - "chunk": A single `DiffContent` as returned by the API.
* - "group": A single `GrDiffGroup` as used for rendering.
* - "common" chunk/group: A chunk/group that should be considered unchanged
* for diffing purposes. This can mean its either actually unchanged, or it
* has only whitespace changes.
* - "key location": A line number and side of the diff that should not be
* collapsed e.g. because a comment is attached to it, or because it was
* provided in the URL and thus should be visible
* - "uncollapsible" chunk/group: A chunk/group that is either not "common",
* or cannot be collapsed because it contains a key location
*
* Here a a number of tasks this processor performs:
* - splitting large chunks to allow more granular async rendering
* - adding a group for the "File" pseudo line that file-level comments can
* be attached to
* - replacing common parts of the diff that are outside the user's
* context setting and do not have comments with a group representing the
* "expand context" widget. This may require splitting a chunk/group so
* that the part that is within the context or has comments is shown, while
* the rest is not.
*/
@customElement('gr-diff-processor')
export class GrDiffProcessor extends GestureEventListeners(
LegacyElementMixin(PolymerElement)
) {
@property({type: Number})
context = 3;
@property({type: Array, notify: true})
groups: GrDiffGroup[] = [];
@property({type: Object})
keyLocations: KeyLocations = {left: {}, right: {}};
@property({type: Number})
_asyncThreshold = 64;
@property({type: Number})
_nextStepHandle: number | null = null;
@property({type: Object})
_processPromise: CancelablePromise<void> | null = null;
@property({type: Boolean})
_isScrolling?: boolean;
/** @override */
attached() {
super.attached();
this.listen(window, 'scroll', '_handleWindowScroll');
}
/** @override */
detached() {
super.detached();
this.cancel();
this.unlisten(window, 'scroll', '_handleWindowScroll');
}
_handleWindowScroll() {
this._isScrolling = true;
this.debounce(
'resetIsScrolling',
() => {
this._isScrolling = false;
},
50
);
}
/**
* Asynchronously process the diff chunks into groups. As it processes, it
* will splice groups into the `groups` property of the component.
*
* @return A promise that resolves with an
* array of GrDiffGroups when the diff is completely processed.
*/
process(chunks: DiffContent[], isBinary: boolean) {
// Cancel any still running process() calls, because they append to the
// same groups field.
this.cancel();
this.groups = [];
this.push('groups', this._makeFileComments());
// If it's a binary diff, we won't be rendering hunks of text differences
// so finish processing.
if (isBinary) {
return Promise.resolve();
}
this._processPromise = util.makeCancelable(
new Promise(resolve => {
const state = {
lineNums: {left: 0, right: 0},
chunkIndex: 0,
};
chunks = this._splitLargeChunks(chunks);
chunks = this._splitCommonChunksWithKeyLocations(chunks);
let currentBatch = 0;
const nextStep = () => {
if (this._isScrolling) {
this._nextStepHandle = this.async(nextStep, 100);
return;
}
// If we are done, resolve the promise.
if (state.chunkIndex >= chunks.length) {
resolve();
this._nextStepHandle = null;
return;
}
// Process the next chunk and incorporate the result.
const stateUpdate = this._processNext(state, chunks);
for (const group of stateUpdate.groups) {
this.push('groups', group);
currentBatch += group.lines.length;
}
state.lineNums.left += stateUpdate.lineDelta.left;
state.lineNums.right += stateUpdate.lineDelta.right;
// Increment the index and recurse.
state.chunkIndex = stateUpdate.newChunkIndex;
if (currentBatch >= this._asyncThreshold) {
currentBatch = 0;
this._nextStepHandle = this.async(nextStep, 1);
} else {
nextStep.call(this);
}
};
nextStep.call(this);
})
);
return this._processPromise.finally(() => {
this._processPromise = null;
});
}
/**
* Cancel any jobs that are running.
*/
cancel() {
if (this._nextStepHandle !== null) {
this.cancelAsync(this._nextStepHandle);
this._nextStepHandle = null;
}
if (this._processPromise) {
this._processPromise.cancel();
}
}
/**
* Process the next uncollapsible chunk, or the next collapsible chunks.
*/
_processNext(state: State, chunks: DiffContent[]) {
const firstUncollapsibleChunkIndex = this._firstUncollapsibleChunkIndex(
chunks,
state.chunkIndex
);
if (firstUncollapsibleChunkIndex === state.chunkIndex) {
const chunk = chunks[state.chunkIndex];
return {
lineDelta: {
left: this._linesLeft(chunk).length,
right: this._linesRight(chunk).length,
},
groups: [
this._chunkToGroup(
chunk,
state.lineNums.left + 1,
state.lineNums.right + 1
),
],
newChunkIndex: state.chunkIndex + 1,
};
}
return this._processCollapsibleChunks(
state,
chunks,
firstUncollapsibleChunkIndex
);
}
_linesLeft(chunk: DiffContent) {
return chunk.ab || chunk.a || [];
}
_linesRight(chunk: DiffContent) {
return chunk.ab || chunk.b || [];
}
_firstUncollapsibleChunkIndex(chunks: DiffContent[], offset: number) {
let chunkIndex = offset;
while (
chunkIndex < chunks.length &&
this._isCollapsibleChunk(chunks[chunkIndex])
) {
chunkIndex++;
}
return chunkIndex;
}
_isCollapsibleChunk(chunk: DiffContent) {
return (chunk.ab || chunk.common || chunk.skip) && !chunk.keyLocation;
}
/**
* Process a stretch of collapsible chunks.
*
* Outputs up to three groups:
* 1) Visible context before the hidden common code, unless it's the
* very beginning of the file.
* 2) Context hidden behind a context bar, unless empty.
* 3) Visible context after the hidden common code, unless it's the very
* end of the file.
*/
_processCollapsibleChunks(
state: State,
chunks: DiffContent[],
firstUncollapsibleChunkIndex: number
) {
const collapsibleChunks = chunks.slice(
state.chunkIndex,
firstUncollapsibleChunkIndex
);
const lineCount = collapsibleChunks.reduce(
(sum, chunk) => sum + this._commonChunkLength(chunk),
0
);
let groups = this._chunksToGroups(
collapsibleChunks,
state.lineNums.left + 1,
state.lineNums.right + 1
);
const hasSkippedGroup = !!groups.find(g => g.skip);
if (this.context !== WHOLE_FILE || hasSkippedGroup) {
const contextNumLines = this.context > 0 ? this.context : 0;
const hiddenStart = state.chunkIndex === 0 ? 0 : contextNumLines;
const hiddenEnd =
lineCount -
(firstUncollapsibleChunkIndex === chunks.length ? 0 : this.context);
groups = hideInContextControl(groups, hiddenStart, hiddenEnd);
}
return {
lineDelta: {
left: lineCount,
right: lineCount,
},
groups,
newChunkIndex: firstUncollapsibleChunkIndex,
};
}
_commonChunkLength(chunk: DiffContent) {
if (chunk.skip) {
return chunk.skip;
}
console.assert(!!chunk.ab || !!chunk.common);
console.assert(
!chunk.a || (!!chunk.b && chunk.a.length === chunk.b.length),
'common chunk needs same number of a and b lines: ',
chunk
);
return this._linesLeft(chunk).length;
}
_chunksToGroups(
chunks: DiffContent[],
offsetLeft: number,
offsetRight: number
): GrDiffGroup[] {
return chunks.map(chunk => {
const group = this._chunkToGroup(chunk, offsetLeft, offsetRight);
const chunkLength = this._commonChunkLength(chunk);
offsetLeft += chunkLength;
offsetRight += chunkLength;
return group;
});
}
_chunkToGroup(
chunk: DiffContent,
offsetLeft: number,
offsetRight: number
): GrDiffGroup {
const type =
chunk.ab || chunk.skip ? GrDiffGroupType.BOTH : GrDiffGroupType.DELTA;
const lines = this._linesFromChunk(chunk, offsetLeft, offsetRight);
const group = new GrDiffGroup(type, lines);
group.keyLocation = !!chunk.keyLocation;
group.dueToRebase = !!chunk.due_to_rebase;
group.moveDetails = chunk.move_details;
group.skip = chunk.skip;
group.ignoredWhitespaceOnly = !!chunk.common;
if (chunk.skip) {
group.lineRange = {
left: {start_line: offsetLeft, end_line: offsetLeft + chunk.skip - 1},
right: {
start_line: offsetRight,
end_line: offsetRight + chunk.skip - 1,
},
};
}
return group;
}
_linesFromChunk(chunk: DiffContent, offsetLeft: number, offsetRight: number) {
if (chunk.ab) {
return chunk.ab.map((row, i) =>
this._lineFromRow(GrDiffLineType.BOTH, offsetLeft, offsetRight, row, i)
);
}
let lines: GrDiffLine[] = [];
if (chunk.a) {
// Avoiding a.push(...b) because that causes callstack overflows for
// large b, which can occur when large files are added removed.
lines = lines.concat(
this._linesFromRows(
GrDiffLineType.REMOVE,
chunk.a,
offsetLeft,
chunk.edit_a
)
);
}
if (chunk.b) {
// Avoiding a.push(...b) because that causes callstack overflows for
// large b, which can occur when large files are added removed.
lines = lines.concat(
this._linesFromRows(
GrDiffLineType.ADD,
chunk.b,
offsetRight,
chunk.edit_b
)
);
}
return lines;
}
_linesFromRows(
lineType: GrDiffLineType,
rows: string[],
offset: number,
intralineInfos?: number[][]
): GrDiffLine[] {
const grDiffHighlights = intralineInfos
? this._convertIntralineInfos(rows, intralineInfos)
: undefined;
return rows.map((row, i) =>
this._lineFromRow(lineType, offset, offset, row, i, grDiffHighlights)
);
}
_lineFromRow(
type: GrDiffLineType,
offsetLeft: number,
offsetRight: number,
row: string,
i: number,
highlights?: Highlights[]
): GrDiffLine {
const line = new GrDiffLine(type);
line.text = row;
if (type !== GrDiffLineType.ADD) line.beforeNumber = offsetLeft + i;
if (type !== GrDiffLineType.REMOVE) line.afterNumber = offsetRight + i;
if (highlights) {
line.hasIntralineInfo = true;
line.highlights = highlights.filter(hl => hl.contentIndex === i);
} else {
line.hasIntralineInfo = false;
}
return line;
}
_makeFileComments() {
const line = new GrDiffLine(GrDiffLineType.BOTH);
line.beforeNumber = FILE;
line.afterNumber = FILE;
return new GrDiffGroup(GrDiffGroupType.BOTH, [line]);
}
/**
* Split chunks into smaller chunks of the same kind.
*
* This is done to prevent doing too much work on the main thread in one
* uninterrupted rendering step, which would make the browser unresponsive.
*
* Note that in the case of unmodified chunks, we only split chunks if the
* context is set to file (because otherwise they are split up further down
* the processing into the visible and hidden context), and only split it
* into 2 chunks, one max sized one and the rest (for reasons that are
* unclear to me).
*
* @param chunks Chunks as returned from the server
* @return Finer grained chunks.
*/
_splitLargeChunks(chunks: DiffContent[]): DiffContent[] {
const newChunks = [];
for (const chunk of chunks) {
if (!chunk.ab) {
for (const subChunk of this._breakdownChunk(chunk)) {
newChunks.push(subChunk);
}
continue;
}
// If the context is set to "whole file", then break down the shared
// chunks so they can be rendered incrementally. Note: this is not
// enabled for any other context preference because manipulating the
// chunks in this way violates assumptions by the context grouper logic.
if (this.context === -1 && chunk.ab.length > MAX_GROUP_SIZE * 2) {
// Split large shared chunks in two, where the first is the maximum
// group size.
newChunks.push({ab: chunk.ab.slice(0, MAX_GROUP_SIZE)});
newChunks.push({ab: chunk.ab.slice(MAX_GROUP_SIZE)});
} else {
newChunks.push(chunk);
}
}
return newChunks;
}
/**
* In order to show key locations, such as comments, out of the bounds of
* the selected context, treat them as separate chunks within the model so
* that the content (and context surrounding it) renders correctly.
*
* @param chunks DiffContents as returned from server.
* @return Finer grained DiffContents.
*/
_splitCommonChunksWithKeyLocations(chunks: DiffContent[]): DiffContent[] {
const result = [];
let leftLineNum = 1;
let rightLineNum = 1;
for (const chunk of chunks) {
// If it isn't a common chunk, append it as-is and update line numbers.
if (!chunk.ab && !chunk.skip && !chunk.common) {
if (chunk.a) {
leftLineNum += chunk.a.length;
}
if (chunk.b) {
rightLineNum += chunk.b.length;
}
result.push(chunk);
continue;
}
if (chunk.common && chunk.a!.length !== chunk.b!.length) {
throw new Error(
'DiffContent with common=true must always have equal length'
);
}
const numLines = this._commonChunkLength(chunk);
const chunkEnds = this._findChunkEndsAtKeyLocations(
numLines,
leftLineNum,
rightLineNum
);
leftLineNum += numLines;
rightLineNum += numLines;
if (chunk.skip) {
result.push({
...chunk,
skip: chunk.skip,
keyLocation: false,
});
} else if (chunk.ab) {
result.push(
...this._splitAtChunkEnds(chunk.ab, chunkEnds).map(
({lines, keyLocation}) => {
return {
...chunk,
ab: lines,
keyLocation,
};
}
)
);
} else if (chunk.common) {
const aChunks = this._splitAtChunkEnds(chunk.a!, chunkEnds);
const bChunks = this._splitAtChunkEnds(chunk.b!, chunkEnds);
result.push(
...aChunks.map(({lines, keyLocation}, i) => {
return {
...chunk,
a: lines,
b: bChunks[i].lines,
keyLocation,
};
})
);
}
}
return result;
}
/**
* @return Offsets of the new chunk ends, including whether it's a key
* location.
*/
_findChunkEndsAtKeyLocations(
numLines: number,
leftOffset: number,
rightOffset: number
): ChunkEnd[] {
const result = [];
let lastChunkEnd = 0;
for (let i = 0; i < numLines; i++) {
// If this line should not be collapsed.
if (
this.keyLocations[Side.LEFT][leftOffset + i] ||
this.keyLocations[Side.RIGHT][rightOffset + i]
) {
// If any lines have been accumulated into the chunk leading up to
// this non-collapse line, then add them as a chunk and start a new
// one.
if (i > lastChunkEnd) {
result.push({offset: i, keyLocation: false});
lastChunkEnd = i;
}
// Add the non-collapse line as its own chunk.
result.push({offset: i + 1, keyLocation: true});
}
}
if (numLines > lastChunkEnd) {
result.push({offset: numLines, keyLocation: false});
}
return result;
}
_splitAtChunkEnds(lines: string[], chunkEnds: ChunkEnd[]) {
const result = [];
let lastChunkEndOffset = 0;
for (const {offset, keyLocation} of chunkEnds) {
result.push({
lines: lines.slice(lastChunkEndOffset, offset),
keyLocation,
});
lastChunkEndOffset = offset;
}
return result;
}
/**
* Converts `IntralineInfo`s return by the API to `GrLineHighlights` used
* for rendering.
*/
_convertIntralineInfos(
rows: string[],
intralineInfos: number[][]
): Highlights[] {
let rowIndex = 0;
let idx = 0;
const normalized = [];
for (const [skipLength, markLength] of intralineInfos) {
let line = rows[rowIndex] + '\n';
let j = 0;
while (j < skipLength) {
if (idx === line.length) {
idx = 0;
line = rows[++rowIndex] + '\n';
continue;
}
idx++;
j++;
}
let lineHighlight: Highlights = {
contentIndex: rowIndex,
startIndex: idx,
};
j = 0;
while (line && j < markLength) {
if (idx === line.length) {
idx = 0;
line = rows[++rowIndex] + '\n';
normalized.push(lineHighlight);
lineHighlight = {
contentIndex: rowIndex,
startIndex: idx,
};
continue;
}
idx++;
j++;
}
lineHighlight.endIndex = idx;
normalized.push(lineHighlight);
}
return normalized;
}
/**
* If a group is an addition or a removal, break it down into smaller groups
* of that type using the MAX_GROUP_SIZE. If the group is a shared chunk
* or a delta it is returned as the single element of the result array.
*/
_breakdownChunk(chunk: DiffContent): DiffContent[] {
let key: 'a' | 'b' | 'ab' | null = null;
const {a, b, ab, move_details} = chunk;
if (a?.length && !b?.length) {
key = 'a';
} else if (b?.length && !a?.length) {
key = 'b';
} else if (ab?.length) {
key = 'ab';
}
// Move chunks should not be divided because of move label
// positioned in the top of the chunk
if (!key || move_details) {
return [chunk];
}
return this._breakdown(chunk[key]!, MAX_GROUP_SIZE).map(subChunkLines => {
const subChunk: DiffContent = {};
subChunk[key!] = subChunkLines;
if (chunk.due_to_rebase) {
subChunk.due_to_rebase = true;
}
if (chunk.move_details) {
subChunk.move_details = chunk.move_details;
}
return subChunk;
});
}
/**
* Given an array and a size, return an array of arrays where no inner array
* is larger than that size, preserving the original order.
*/
_breakdown<T>(array: T[], size: number): T[][] {
if (!array.length) {
return [];
}
if (array.length < size) {
return [array];
}
const head = array.slice(0, array.length - size);
const tail = array.slice(array.length - size);
return this._breakdown(head, size).concat([tail]);
}
}
declare global {
interface HTMLElementTagNameMap {
'gr-diff-processor': GrDiffProcessor;
}
}