front_end/models/source_map_scopes/FunctionCodeResolver.ts

// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import type * as Platform from '../../core/platform/platform.js';
import * as SDK from '../../core/sdk/sdk.js';
import * as Bindings from '../bindings/bindings.js';
import * as Formatter from '../formatter/formatter.js';
import * as TextUtils from '../text_utils/text_utils.js';
import * as Workspace from '../workspace/workspace.js';

/** Represents the source code for a given function, including additional context of surrounding lines. */
export interface FunctionCode {
  functionBounds: Workspace.UISourceCode.UIFunctionBounds;
  /** The text of `uiSourceCode`. */
  text: TextUtils.Text.Text;
  /** The function text. */
  code: string;
  /** The range of `code` within `text`. */
  range: TextUtils.TextRange.TextRange;
  /** The function text, plus some additional context before and after. The actual function is wrapped in <FUNCTION_START>...<FUNCTION_END> */
  codeWithContext: string;
  /** The range of `codeWithContext` within `text`. */
  rangeWithContext: TextUtils.TextRange.TextRange;
}

export interface CreateFunctionCodeOptions {
  /** Number of characters to include before and after the function. Stacks with `contextLineLength`. */
  contextLength?: number;
  /** Number of lines to include before and after the function. Stacks with `contextLength`. */
  contextLineLength?: number;
  /** If true, appends profile data from the trace at the end of every line of the function in `codeWithContext`. This should match what is seen in the formatted view in the Sources panel. */
  appendProfileData?: boolean;
}

interface InputData {
  text: TextUtils.Text.Text;
  formattedContent: Formatter.ScriptFormatter.FormattedContent|null;
  performanceData: Workspace.UISourceCode.LineColumnProfileMap|undefined;
}

const inputCache = new WeakMap<Workspace.UISourceCode.UISourceCode, Promise<InputData>>();

async function prepareInput(uiSourceCode: Workspace.UISourceCode.UISourceCode, content: string): Promise<InputData> {
  const formattedContent = await format(uiSourceCode, content);
  const text = new TextUtils.Text.Text(formattedContent ? formattedContent.formattedContent : content);
  let performanceData = uiSourceCode.getDecorationData(Workspace.UISourceCode.DecoratorType.PERFORMANCE) as
          Workspace.UISourceCode.LineColumnProfileMap |
      undefined;

  // Map profile data to the formatted view of the text.
  if (formattedContent && performanceData) {
    performanceData = Workspace.UISourceCode.createMappedProfileData(performanceData, (line, column) => {
      return formattedContent.formattedMapping.originalToFormatted(line, column);
    });
  }

  return {text, formattedContent, performanceData};
}

/** Formatting and parsing line endings for Text is expensive, so cache it. */
async function prepareInputAndCache(
    uiSourceCode: Workspace.UISourceCode.UISourceCode, content: string): Promise<InputData> {
  let cachedPromise = inputCache.get(uiSourceCode);
  if (cachedPromise) {
    return await cachedPromise;
  }

  cachedPromise = prepareInput(uiSourceCode, content);
  inputCache.set(uiSourceCode, cachedPromise);
  return await cachedPromise;
}

function extractPerformanceDataByLine(
    textRange: TextUtils.TextRange.TextRange, performanceData: Workspace.UISourceCode.LineColumnProfileMap): number[] {
  const {startLine, startColumn, endLine, endColumn} = textRange;
  const byLine = new Array(endLine - startLine + 1).fill(0);

  for (let line = startLine; line <= endLine; line++) {
    const lineData = performanceData.get(line + 1);
    if (!lineData) {
      continue;
    }

    // Fast-path for when the entire line's data is relevant.
    if (line !== startLine && line !== endLine) {
      byLine[line - startLine] = lineData.values().reduce((acc, cur) => acc + cur);
      continue;
    }

    const column0 = line === startLine ? startColumn + 1 : 0;
    const column1 = line === endLine ? endColumn + 1 : Number.POSITIVE_INFINITY;

    let totalData = 0;
    for (const [column, data] of lineData) {
      if (column >= column0 && column <= column1) {
        totalData += data;
      }
    }

    byLine[line - startLine] = totalData;
  }

  return byLine.map(data => Math.round(data * 10) / 10);
}

function createFunctionCode(
    inputData: InputData, functionBounds: Workspace.UISourceCode.UIFunctionBounds,
    options?: CreateFunctionCodeOptions): FunctionCode {
  let {startLine, startColumn, endLine, endColumn} = functionBounds.range;
  if (inputData.formattedContent) {
    const startMapped = inputData.formattedContent.formattedMapping.originalToFormatted(startLine, startColumn);
    startLine = startMapped[0];
    startColumn = startMapped[1];

    const endMapped = inputData.formattedContent.formattedMapping.originalToFormatted(endLine, endColumn);
    endLine = endMapped[0];
    endColumn = endMapped[1];
  }

  const text = inputData.text;
  const content = text.value();

  // Define two ranges - the first is just the function bounds, the second includes
  // that plus some surrounding context as dictated by the options.
  const range = new TextUtils.TextRange.TextRange(startLine, startColumn, endLine, endColumn);

  const functionStartOffset = text.offsetFromPosition(startLine, startColumn);
  const functionEndOffset = text.offsetFromPosition(endLine, endColumn);

  let contextStartOffset = 0;
  if (options?.contextLength !== undefined) {
    const contextLength = options.contextLength;
    contextStartOffset = Math.max(contextStartOffset, functionStartOffset - contextLength);
  }
  if (options?.contextLineLength !== undefined) {
    const contextLineLength = options.contextLineLength;
    const position = text.offsetFromPosition(Math.max(startLine - contextLineLength, 0), 0);
    contextStartOffset = Math.max(contextStartOffset, position);
  }

  let contextEndOffset = content.length;
  if (options?.contextLength !== undefined) {
    const contextLength = options.contextLength;
    contextEndOffset = Math.min(contextEndOffset, functionEndOffset + contextLength);
  }
  if (options?.contextLineLength !== undefined) {
    const contextLineLength = options.contextLineLength;
    const position =
        text.offsetFromPosition(Math.min(endLine + contextLineLength, text.lineCount() - 1), Number.POSITIVE_INFINITY);
    contextEndOffset = Math.min(contextEndOffset, position);
  }

  const contextStart = text.positionFromOffset(contextStartOffset);
  const contextEnd = text.positionFromOffset(contextEndOffset);
  const rangeWithContext = new TextUtils.TextRange.TextRange(
      contextStart.lineNumber, contextStart.columnNumber, contextEnd.lineNumber, contextEnd.columnNumber);

  // Grab substrings for the function range, and for the context range.
  const code = content.substring(functionStartOffset, functionEndOffset);
  const before = content.substring(contextStartOffset, functionStartOffset);
  const after = content.substring(functionEndOffset, contextEndOffset);

  let codeWithContext;
  if (options?.appendProfileData && inputData.performanceData) {
    const performanceDataByLine = extractPerformanceDataByLine(range, inputData.performanceData);
    const lines = performanceDataByLine.map((data, i) => {
      let line = text.lineAt(startLine + i);

      const isLastLine = i === performanceDataByLine.length - 1;
      if (i === 0) {
        if (isLastLine) {
          line = line.substring(startColumn, endColumn);
        } else {
          line = line.substring(startColumn);
        }
      } else if (isLastLine) {
        line = line.substring(0, endColumn);
      }

      if (isLastLine) {
        // Don't ever annotate the last line - it could make the rest of the code on
        // that line get commented out.
        data = 0;
      }

      return data ? `${line} // ${data} ms` : line;
    });
    const annotatedCode = lines.join('\n');
    codeWithContext = before + `<FUNCTION_START>${annotatedCode}<FUNCTION_END>` + after;
  } else {
    codeWithContext = before + `<FUNCTION_START>${code}<FUNCTION_END>` + after;
  }

  return {
    functionBounds,
    text,
    code,
    range,
    codeWithContext,
    rangeWithContext,
  };
}

/**
 * The input location may be a source mapped location or a raw location.
 */
export async function getFunctionCodeFromLocation(
    target: SDK.Target.Target, url: Platform.DevToolsPath.UrlString, line: number, column: number,
    options?: CreateFunctionCodeOptions): Promise<FunctionCode|null> {
  const debuggerModel = target.model(SDK.DebuggerModel.DebuggerModel);
  if (!debuggerModel) {
    throw new Error('missing debugger model');
  }

  let uiSourceCode;
  const debuggerWorkspaceBinding = Bindings.DebuggerWorkspaceBinding.DebuggerWorkspaceBinding.instance();
  const projects = debuggerWorkspaceBinding.workspace.projectsForType(Workspace.Workspace.projectTypes.Network);
  for (const project of projects) {
    uiSourceCode = project.uiSourceCodeForURL(url);
    if (uiSourceCode) {
      break;
    }
  }

  if (!uiSourceCode) {
    return null;
  }

  const rawLocations = await debuggerWorkspaceBinding.uiLocationToRawLocations(uiSourceCode, line, column);
  const rawLocation = rawLocations.at(-1);
  if (!rawLocation) {
    return null;
  }

  return await getFunctionCodeFromRawLocation(rawLocation, options);
}

async function format(uiSourceCode: Workspace.UISourceCode.UISourceCode, content: string):
    Promise<Formatter.ScriptFormatter.FormattedContent|null> {
  const contentType = uiSourceCode.contentType();
  const shouldFormat = !contentType.isFromSourceMap() && (contentType.isDocument() || contentType.isScript()) &&
      TextUtils.TextUtils.isMinified(content);
  if (!shouldFormat) {
    return null;
  }

  return await Formatter.ScriptFormatter.formatScriptContent(contentType.canonicalMimeType(), content, '\t');
}

/**
 * Returns a {@link FunctionCode} for the given raw location.
 */
export async function getFunctionCodeFromRawLocation(
    rawLocation: SDK.DebuggerModel.Location, options?: CreateFunctionCodeOptions): Promise<FunctionCode|null> {
  const debuggerWorkspaceBinding = Bindings.DebuggerWorkspaceBinding.DebuggerWorkspaceBinding.instance();
  const functionBounds = await debuggerWorkspaceBinding.functionBoundsAtRawLocation(rawLocation);
  if (!functionBounds) {
    return null;
  }

  await functionBounds.uiSourceCode.requestContentData();
  const content = functionBounds.uiSourceCode.content();
  if (!content) {
    return null;
  }

  const inputData = await prepareInputAndCache(functionBounds.uiSourceCode, content);
  return createFunctionCode(inputData, functionBounds, options);
}