Function deriveNewContentsFromChunks

packages/arctic/src/patch/index.ts:300–333

(filePath: string, chunks: UpdateFileChunk[])

  }

  export function deriveNewContentsFromChunks(filePath: string, chunks: UpdateFileChunk[]): ApplyPatchFileUpdate {
    // Read original file content
    let originalContent: string
    try {
      originalContent = require("fs").readFileSync(filePath, "utf-8")
    } catch (error) {
      throw new Error(`Failed to read file ${filePath}: ${error}`)
    }

    let originalLines = originalContent.split("\n")

    // Drop trailing empty element for consistent line counting
    if (originalLines.length > 0 && originalLines[originalLines.length - 1] === "") {
      originalLines.pop()
    }

    const replacements = computeReplacements(originalLines, filePath, chunks)
    let newLines = applyReplacements(originalLines, replacements)

    // Ensure trailing newline
    if (newLines.length === 0 || newLines[newLines.length - 1] !== "") {
      newLines.push("")
    }

    const newContent = newLines.join("\n")

    // Generate unified diff
    const unifiedDiff = generateUnifiedDiff(originalContent, newContent)

    return {
      unified_diff: unifiedDiff,
      content: newContent,
    }
  }

  function computeReplacements(
    originalLines: string[],