chore(audoedit): simplify diff utils and renderer data structures (#6172

)

- No functional changes.
- Simplifies data structures used to calculate the diff between the
current document content and predicted edits.
- Simplifies data structures used to render autoedit decorations. 
- Removes redundant data structures and transformations happening
between the diff calculation and the renderer call.
- Adds granular `changes: LineChange` to `ModifiedLineInfo`,
representing individual insertions and deletions in modified lines. This
is helpful for troubleshooting purposes, and I plan to use it for the
experimental inline renderer implementation that we discussed recently
in Slack.
- Updates the default autoedits renderer to use all the above changes.

vscode/src/autoedits/renderer/decorators/base.ts

@@ -1,5 +1,4 @@
 import type * as vscode from 'vscode'
-import type { ModifiedRange } from '../diff-utils'
 
 /**
  * Represents a decorator that manages VS Code editor decorations for auto-edit suggestions.
@@ -8,63 +7,77 @@ import type { ModifiedRange } from '../diff-utils'
  * that visualize proposed text changes in the editor.
  *
  * Lifecycle:
- * - Single instance should be created per decoration session and disposed of when the decorations
+ * - A single instance should be created per decoration session and disposed of when the decorations
  *   are no longer needed.
  * - Always call dispose() when the decorator is no longer needed to clean up resources.
  * - Dispose should always clear the decorations.
  *
  * Usage Pattern:
  * ```typescript
- * const decorator = createAutoeditsDecorator(...);
+ * const decorator = createAutoEditsDecorator(...);
  * try {
  *   decorator.setDecorations(decorationInfo);
  *   ...
  * } finally {
- *   decorator.clearDecorations();
  *   decorator.dispose();
  * }
  * ```
  */
-export interface AutoeditsDecorator extends vscode.Disposable {
+export interface AutoEditsDecorator extends vscode.Disposable {
     /**
      * Applies decorations to the editor based on the provided decoration information.
      *
-     * @param decorationInformation Contains the line-by-line information about text changes
+     * @param decorationInfo Contains the line-by-line information about text changes
      *        and how they should be decorated in the editor.
      */
-    setDecorations(decorationInformation: DecorationInformation): void
+    setDecorations(decorationInfo: DecorationInfo): void
 }
 
 /**
- * Represents the different types of line decorations that can be applied.
+ * Represents a line of text with its change type and content.
  */
-export enum DecorationLineType {
-    /** Line has been modified from its original state */
-    Modified = 0,
-    /** New line has been added */
-    Added = 1,
-    /** Line has been removed */
-    Removed = 2,
-    /** Line remains unchanged */
-    Unchanged = 3,
+export type DecorationLineInfo = AddedLineInfo | RemovedLineInfo | ModifiedLineInfo | UnchangedLineInfo
+
+export interface AddedLineInfo {
+    type: 'added'
+    text: string
+    /** `lineNumber` in the modified text */
+    lineNumber: number
+}
+
+export interface RemovedLineInfo {
+    type: 'removed'
+    text: string
+    /** `lineNumber` in the original text */
+    lineNumber: number
 }
 
-export interface DecorationLineInformation {
-    lineType: DecorationLineType
-    // Line number in the original text. The line number can be null if the line was added.
-    oldLineNumber: number | null
-    // Line number in the new predicted text. The line number can be null if the line was removed.
-    newLineNumber: number | null
-    // The text of the line in the original text.
+export interface ModifiedLineInfo {
+    type: 'modified'
     oldText: string
-    // The text of the line in the new predicted text.
     newText: string
-    // The ranges of text that were modified in the line.
-    modifiedRanges: ModifiedRange[]
+    changes: LineChange[]
+    /** `lineNumber` in the modified text */
+    lineNumber: number
+}
+
+export interface UnchangedLineInfo {
+    type: 'unchanged'
+    text: string
+    /** `lineNumber` in the modified text */
+    lineNumber: number
+}
+
+export type LineChange = {
+    type: 'insert' | 'delete'
+    /** `range` in the modified text relative to the document start */
+    range: vscode.Range
+    text: string
 }
 
-export interface DecorationInformation {
-    lines: DecorationLineInformation[]
-    oldLines: string[]
-    newLines: string[]
+export interface DecorationInfo {
+    modifiedLines: ModifiedLineInfo[]
+    removedLines: RemovedLineInfo[]
+    addedLines: AddedLineInfo[]
+    unchangedLines: UnchangedLineInfo[]
 }