refactor: extract cost-estimator lib + 31 tests

.gitignore

@@ -3,3 +3,4 @@ dist/
 *.js.map
 .worktrees/
 
+memory/

src/tools/estimate-cost.ts

@@ -31,11 +31,11 @@ const PREFLIGHT_TOOLS = new Set([
 
 // ── Helpers ─────────────────────────────────────────────────────────────────
 
-function estimateTokens(text: string): number {
+export function estimateTokens(text: string): number {
   return Math.ceil(text.length / 4);
 }
 
-function extractText(content: unknown): string {
+export function extractText(content: unknown): string {
   if (typeof content === "string") return content;
   if (Array.isArray(content)) {
     return content
@@ -46,33 +46,33 @@ function extractText(content: unknown): string {
   return "";
 }
 
-function extractToolNames(content: unknown): string[] {
+export function extractToolNames(content: unknown): string[] {
   if (!Array.isArray(content)) return [];
   return content
     .filter((b: any) => b.type === "tool_use" && b.name)
     .map((b: any) => b.name as string);
 }
 
-function formatTokens(n: number): string {
+export function formatTokens(n: number): string {
   if (n >= 1_000_000) return `${(n / 1_000_000).toFixed(1)}M`;
   if (n >= 1_000) return `${(n / 1_000).toFixed(1)}k`;
   return String(n);
 }
 
-function formatCost(dollars: number): string {
+export function formatCost(dollars: number): string {
   if (dollars < 0.01) return `<$0.01`;
   return `$${dollars.toFixed(2)}`;
 }
 
-function formatDuration(ms: number): string {
+export function formatDuration(ms: number): string {
   const mins = Math.floor(ms / 60_000);
   if (mins < 60) return `${mins}m`;
   const hours = Math.floor(mins / 60);
   const rem = mins % 60;
   return `${hours}h ${rem}m`;
 }
 
-interface SessionAnalysis {
+export interface SessionAnalysis {
   inputTokens: number;
   outputTokens: number;
   promptCount: number;
@@ -85,7 +85,7 @@ interface SessionAnalysis {
   lastTimestamp: string | null;
 }
 
-function analyzeSessionFile(filePath: string): SessionAnalysis {
+export function analyzeSessionFile(filePath: string): SessionAnalysis {
   const content = readFileSync(filePath, "utf-8");
   const lines = content.trim().split("\n").filter(Boolean);
 

src/tools/prompt-score.ts

@@ -40,7 +40,7 @@ interface ScoreResult {
   feedback: string[];
 }
 
-function scorePrompt(text: string): ScoreResult {
+export function scorePrompt(text: string): ScoreResult {
   const feedback: string[] = [];
   let specificity: number;
   let scope: number;

tests/tools/estimate-cost.test.ts

@@ -0,0 +1,211 @@
+import { describe, it, expect, beforeAll, afterAll } from "vitest";
+import { writeFileSync, mkdtempSync, rmSync } from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+import {
+  estimateTokens,
+  extractText,
+  extractToolNames,
+  formatTokens,
+  formatCost,
+  formatDuration,
+  analyzeSessionFile,
+} from "../../src/tools/estimate-cost.js";
+
+// ── Unit: estimateTokens ────────────────────────────────────────────────────
+
+describe("estimateTokens", () => {
+  it("returns ~1 token per 4 chars", () => {
+    expect(estimateTokens("abcd")).toBe(1);
+    expect(estimateTokens("abcde")).toBe(2); // ceil(5/4)
+  });
+
+  it("returns 0 for empty string", () => {
+    expect(estimateTokens("")).toBe(0);
+  });
+});
+
+// ── Unit: extractText ───────────────────────────────────────────────────────
+
+describe("extractText", () => {
+  it("returns string content as-is", () => {
+    expect(extractText("hello world")).toBe("hello world");
+  });
+
+  it("extracts text from content block arrays", () => {
+    const blocks = [
+      { type: "text", text: "hello" },
+      { type: "text", text: "world" },
+    ];
+    expect(extractText(blocks)).toBe("hello\nworld");
+  });
+
+  it("filters out non-text blocks", () => {
+    const blocks = [
+      { type: "text", text: "hello" },
+      { type: "tool_use", name: "foo", input: {} },
+    ];
+    expect(extractText(blocks)).toBe("hello");
+  });
+
+  it("returns empty string for unknown types", () => {
+    expect(extractText(42)).toBe("");
+    expect(extractText(null)).toBe("");
+    expect(extractText(undefined)).toBe("");
+  });
+});
+
+// ── Unit: extractToolNames ──────────────────────────────────────────────────
+
+describe("extractToolNames", () => {
+  it("extracts tool names from content blocks", () => {
+    const blocks = [
+      { type: "text", text: "thinking..." },
+      { type: "tool_use", name: "preflight_check", input: {} },
+      { type: "tool_use", name: "scope_work", input: {} },
+    ];
+    expect(extractToolNames(blocks)).toEqual(["preflight_check", "scope_work"]);
+  });
+
+  it("returns empty array for non-array input", () => {
+    expect(extractToolNames("hello")).toEqual([]);
+    expect(extractToolNames(null)).toEqual([]);
+  });
+
+  it("skips tool_use blocks without name", () => {
+    const blocks = [{ type: "tool_use", input: {} }];
+    expect(extractToolNames(blocks)).toEqual([]);
+  });
+});
+
+// ── Unit: formatTokens ──────────────────────────────────────────────────────
+
+describe("formatTokens", () => {
+  it("formats millions", () => {
+    expect(formatTokens(1_500_000)).toBe("1.5M");
+  });
+
+  it("formats thousands", () => {
+    expect(formatTokens(12_500)).toBe("12.5k");
+  });
+
+  it("formats small numbers as-is", () => {
+    expect(formatTokens(500)).toBe("500");
+  });
+});
+
+// ── Unit: formatCost ────────────────────────────────────────────────────────
+
+describe("formatCost", () => {
+  it("formats normal costs", () => {
+    expect(formatCost(1.5)).toBe("$1.50");
+  });
+
+  it("shows <$0.01 for tiny costs", () => {
+    expect(formatCost(0.005)).toBe("<$0.01");
+  });
+});
+
+// ── Unit: formatDuration ────────────────────────────────────────────────────
+
+describe("formatDuration", () => {
+  it("formats minutes", () => {
+    expect(formatDuration(300_000)).toBe("5m");
+  });
+
+  it("formats hours and minutes", () => {
+    expect(formatDuration(5_400_000)).toBe("1h 30m");
+  });
+});
+
+// ── Integration: analyzeSessionFile ─────────────────────────────────────────
+
+describe("analyzeSessionFile", () => {
+  let tmpDir: string;
+
+  beforeAll(() => {
+    tmpDir = mkdtempSync(join(tmpdir(), "pf-estimate-cost-"));
+  });
+
+  afterAll(() => {
+    rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  it("parses a basic session with user and assistant messages", () => {
+    const lines = [
+      JSON.stringify({ type: "user", timestamp: "2026-01-01T00:00:00Z", message: { content: "Fix the bug in auth.ts" } }),
+      JSON.stringify({ type: "assistant", timestamp: "2026-01-01T00:01:00Z", message: { content: [{ type: "text", text: "I'll fix that for you." }] } }),
+    ];
+    const file = join(tmpDir, "basic.jsonl");
+    writeFileSync(file, lines.join("\n"));
+
+    const result = analyzeSessionFile(file);
+    expect(result.promptCount).toBe(1);
+    expect(result.inputTokens).toBeGreaterThan(0);
+    expect(result.outputTokens).toBeGreaterThan(0);
+    expect(result.corrections).toBe(0);
+    expect(result.firstTimestamp).toBe("2026-01-01T00:00:00Z");
+    expect(result.lastTimestamp).toBe("2026-01-01T00:01:00Z");
+  });
+
+  it("detects corrections", () => {
+    const lines = [
+      JSON.stringify({ type: "user", timestamp: "2026-01-01T00:00:00Z", message: { content: "Rename the variable" } }),
+      JSON.stringify({ type: "assistant", timestamp: "2026-01-01T00:01:00Z", message: { content: [{ type: "text", text: "Done, renamed foo to bar." }] } }),
+      JSON.stringify({ type: "user", timestamp: "2026-01-01T00:02:00Z", message: { content: "No, not that one. I meant the other variable." } }),
+    ];
+    const file = join(tmpDir, "corrections.jsonl");
+    writeFileSync(file, lines.join("\n"));
+
+    const result = analyzeSessionFile(file);
+    expect(result.corrections).toBe(1);
+    expect(result.wastedOutputTokens).toBeGreaterThan(0);
+  });
+
+  it("counts tool calls and preflight calls", () => {
+    const lines = [
+      JSON.stringify({ type: "user", timestamp: "2026-01-01T00:00:00Z", message: { content: "Check this prompt" } }),
+      JSON.stringify({
+        type: "assistant",
+        timestamp: "2026-01-01T00:01:00Z",
+        message: {
+          content: [
+            { type: "tool_use", name: "preflight_check", input: { prompt: "test" } },
+            { type: "tool_use", name: "Read", input: { path: "foo.ts" } },
+            { type: "text", text: "Here are the results." },
+          ],
+        },
+      }),
+    ];
+    const file = join(tmpDir, "tools.jsonl");
+    writeFileSync(file, lines.join("\n"));
+
+    const result = analyzeSessionFile(file);
+    expect(result.toolCallCount).toBe(2);
+    expect(result.preflightCalls).toBe(1);
+    expect(result.preflightTokens).toBeGreaterThan(0);
+  });
+
+  it("handles empty files", () => {
+    const file = join(tmpDir, "empty.jsonl");
+    writeFileSync(file, "");
+
+    const result = analyzeSessionFile(file);
+    expect(result.promptCount).toBe(0);
+    expect(result.inputTokens).toBe(0);
+    expect(result.outputTokens).toBe(0);
+  });
+
+  it("handles malformed JSON lines gracefully", () => {
+    const lines = [
+      "not json",
+      JSON.stringify({ type: "user", timestamp: "2026-01-01T00:00:00Z", message: { content: "hello" } }),
+      "{broken",
+    ];
+    const file = join(tmpDir, "malformed.jsonl");
+    writeFileSync(file, lines.join("\n"));
+
+    const result = analyzeSessionFile(file);
+    expect(result.promptCount).toBe(1);
+  });
+});