packages/cli/src/__tests__/logs.test.ts

@@ -0,0 +1,250 @@
+/**
+ * Tests for nerve logs command — pure helper functions only.
+ *
+ * We test sliceLogs and buildLogFooter without touching the filesystem or
+ * spawning a real process.
+ */
+
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+import { DEFAULT_LOG_LINES, buildLogFooter, readAllLines, sliceLogs } from "../commands/logs.js";
+import { logsCommand } from "../commands/logs.js";
+
+// ---------------------------------------------------------------------------
+// sliceLogs
+// ---------------------------------------------------------------------------
+
+describe("sliceLogs", () => {
+  const make = (n: number) => Array.from({ length: n }, (_, i) => `line ${i + 1}`);
+
+  it("returns empty result for empty array", () => {
+    const r = sliceLogs([], 0, 50);
+    expect(r.lines).toHaveLength(0);
+    expect(r.total).toBe(0);
+    expect(r.nextOffset).toBeNull();
+  });
+
+  it("tail mode (offset=0): returns last N lines", () => {
+    const lines = make(100);
+    const r = sliceLogs(lines, 0, 10);
+    expect(r.lines).toHaveLength(10);
+    expect(r.lines[0]).toBe("line 91");
+    expect(r.lines[9]).toBe("line 100");
+    expect(r.startLine).toBe(91);
+    expect(r.endLine).toBe(100);
+  });
+
+  it("tail mode: when file shorter than limit, returns all", () => {
+    const lines = make(20);
+    const r = sliceLogs(lines, 0, 50);
+    expect(r.lines).toHaveLength(20);
+    expect(r.startLine).toBe(1);
+    expect(r.endLine).toBe(20);
+    expect(r.nextOffset).toBeNull();
+  });
+
+  it("tail mode: provides nextOffset when earlier lines exist", () => {
+    const lines = make(200);
+    const r = sliceLogs(lines, 0, 50);
+    expect(r.nextOffset).not.toBeNull();
+    expect(r.nextOffset).toBe(151 - 50); // startLine=151, prev page starts at 101
+  });
+
+  it("tail mode: nextOffset is null when showing from line 1", () => {
+    const lines = make(40);
+    const r = sliceLogs(lines, 0, 50);
+    expect(r.nextOffset).toBeNull();
+  });
+
+  it("offset mode: starts at given 1-based line number", () => {
+    const lines = make(100);
+    const r = sliceLogs(lines, 10, 5);
+    expect(r.lines[0]).toBe("line 10");
+    expect(r.startLine).toBe(10);
+    expect(r.endLine).toBe(14);
+  });
+
+  it("offset mode: clamps start to 0 for offset=1", () => {
+    const lines = make(50);
+    const r = sliceLogs(lines, 1, 10);
+    expect(r.startLine).toBe(1);
+  });
+
+  it("offset mode: nextOffset is null when slice starts at line 1", () => {
+    const lines = make(50);
+    const r = sliceLogs(lines, 1, 20);
+    expect(r.nextOffset).toBeNull();
+  });
+
+  it("offset mode: nextOffset points to previous page", () => {
+    const lines = make(100);
+    const r = sliceLogs(lines, 51, 50); // lines 51-100
+    expect(r.nextOffset).toBe(1); // previous page starts at line 1
+  });
+});
+
+// ---------------------------------------------------------------------------
+// buildLogFooter
+// ---------------------------------------------------------------------------
+
+describe("buildLogFooter", () => {
+  it("returns empty-file message when total=0", () => {
+    const slice = { lines: [], total: 0, startLine: 0, endLine: 0, nextOffset: null };
+    expect(buildLogFooter(slice, 50, "/path/to/nerve.log")).toContain("empty");
+  });
+
+  it("includes range and path in footer", () => {
+    const slice = { lines: ["x"], total: 200, startLine: 151, endLine: 200, nextOffset: 101 };
+    const footer = buildLogFooter(slice, 50, "/var/log/nerve.log");
+    expect(footer).toContain("lines 151-200 of 200");
+    expect(footer).toContain("/var/log/nerve.log");
+  });
+
+  it("includes pagination hint when nextOffset is set", () => {
+    const slice = { lines: ["x"], total: 200, startLine: 151, endLine: 200, nextOffset: 101 };
+    const footer = buildLogFooter(slice, 50, "/path/nerve.log");
+    expect(footer).toContain("nerve logs --offset 101 -n 50");
+  });
+
+  it("no pagination hint when nextOffset is null", () => {
+    const slice = { lines: ["x"], total: 20, startLine: 1, endLine: 20, nextOffset: null };
+    const footer = buildLogFooter(slice, 50, "/path/nerve.log");
+    expect(footer).not.toContain("nerve logs --offset");
+  });
+});
+
+// ---------------------------------------------------------------------------
+// DEFAULT_LOG_LINES constant
+// ---------------------------------------------------------------------------
+
+describe("DEFAULT_LOG_LINES", () => {
+  it("is 50", () => {
+    expect(DEFAULT_LOG_LINES).toBe(50);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// readAllLines
+// ---------------------------------------------------------------------------
+
+describe("readAllLines", () => {
+  let tmpDir: string;
+
+  beforeEach(() => {
+    tmpDir = mkdtempSync(join(tmpdir(), "nerve-logs-test-"));
+  });
+
+  afterEach(() => {
+    rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  it("returns empty array for nonexistent file", async () => {
+    const result = await readAllLines(join(tmpDir, "missing.log"));
+    expect(result).toHaveLength(0);
+  });
+
+  it("reads all lines from a file", async () => {
+    const logFile = join(tmpDir, "test.log");
+    writeFileSync(logFile, "line1\nline2\nline3\n");
+    const result = await readAllLines(logFile);
+    expect(result).toEqual(["line1", "line2", "line3"]);
+  });
+
+  it("handles file with no trailing newline", async () => {
+    const logFile = join(tmpDir, "test.log");
+    writeFileSync(logFile, "a\nb\nc");
+    const result = await readAllLines(logFile);
+    expect(result).toEqual(["a", "b", "c"]);
+  });
+
+  it("returns empty array for empty file", async () => {
+    const logFile = join(tmpDir, "empty.log");
+    writeFileSync(logFile, "");
+    const result = await readAllLines(logFile);
+    expect(result).toHaveLength(0);
+  });
+});
+
+// ---------------------------------------------------------------------------
+// Integration: readAllLines + sliceLogs end-to-end
+// ---------------------------------------------------------------------------
+
+describe("readAllLines + sliceLogs integration", () => {
+  let tmpDir: string;
+
+  beforeEach(() => {
+    tmpDir = mkdtempSync(join(tmpdir(), "nerve-logs-int-"));
+  });
+
+  afterEach(() => {
+    rmSync(tmpDir, { recursive: true, force: true });
+  });
+
+  it("tail-paginates a large log file correctly", async () => {
+    const logFile = join(tmpDir, "big.log");
+    const content = Array.from({ length: 120 }, (_, i) => `entry ${i + 1}`).join("\n");
+    writeFileSync(logFile, content);
+
+    const all = await readAllLines(logFile);
+    const page1 = sliceLogs(all, 0, 50); // last 50: lines 71-120
+    expect(page1.startLine).toBe(71);
+    expect(page1.endLine).toBe(120);
+    expect(page1.nextOffset).toBe(21); // max(1, 71-50)
+
+    const page2 = sliceLogs(all, page1.nextOffset!, 50); // lines 21-70
+    expect(page2.startLine).toBe(21);
+    expect(page2.endLine).toBe(70);
+    expect(page2.nextOffset).toBe(1); // max(1, 21-50) = 1
+
+    const page3 = sliceLogs(all, page2.nextOffset!, 50); // lines 1-50
+    expect(page3.startLine).toBe(1);
+    expect(page3.endLine).toBe(50);
+    expect(page3.nextOffset).toBeNull();
+  });
+});
+
+// ---------------------------------------------------------------------------
+// logsCommand: negative offset validation
+// ---------------------------------------------------------------------------
+
+describe("logsCommand negative offset", () => {
+  let stderrOutput: string;
+  let exitCode: number | undefined;
+
+  beforeEach(() => {
+    stderrOutput = "";
+    exitCode = undefined;
+    vi.spyOn(process.stderr, "write").mockImplementation((chunk) => {
+      stderrOutput += typeof chunk === "string" ? chunk : chunk.toString();
+      return true;
+    });
+    vi.spyOn(process, "exit").mockImplementation((code?: number | string | null) => {
+      exitCode = typeof code === "number" ? code : 1;
+      throw new Error(`process.exit(${exitCode})`);
+    });
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it("exits with code 1 and writes to stderr when offset is negative", async () => {
+    await expect(
+      logsCommand.run!({ args: { n: "50", offset: "-5", follow: false }, rawArgs: [], cmd: logsCommand as never }),
+    ).rejects.toThrow("process.exit(1)");
+    expect(exitCode).toBe(1);
+    expect(stderrOutput).toContain("--offset must be a non-negative integer");
+    expect(stderrOutput).toContain("-5");
+  });
+
+  it("exits with code 1 for offset=-1", async () => {
+    await expect(
+      logsCommand.run!({ args: { n: "10", offset: "-1", follow: false }, rawArgs: [], cmd: logsCommand as never }),
+    ).rejects.toThrow("process.exit(1)");
+    expect(exitCode).toBe(1);
+  });
+});

packages/cli/src/cli.ts

@@ -3,6 +3,7 @@
 import { defineCommand, runMain } from "citty";
 
 import { initCommand } from "./commands/init.js";
+import { logsCommand } from "./commands/logs.js";
 import { startCommand } from "./commands/start.js";
 import { statusCommand } from "./commands/status.js";
 import { stopCommand } from "./commands/stop.js";
@@ -19,6 +20,7 @@ const main = defineCommand({
     start: startCommand,
     stop: stopCommand,
     status: statusCommand,
+    logs: logsCommand,
     validate: validateCommand,
     workflow: workflowCommand,
   },

packages/cli/src/commands/logs.ts

@@ -0,0 +1,197 @@
+import { createReadStream, existsSync, statSync } from "node:fs";
+import { createInterface } from "node:readline";
+
+import { defineCommand } from "citty";
+
+import { getLogPath } from "../workspace.js";
+
+export const DEFAULT_LOG_LINES = 50;
+
+const sleep = (ms: number) => new Promise<void>((resolve) => setTimeout(resolve, ms));
+
+/**
+ * Read all lines from a file. Returns empty array if file does not exist.
+ *
+ * TODO: For tail mode (offset=0), avoid reading the whole file into memory by
+ * seeking to the last N bytes via createReadStream({ start: max(0, size - CHUNK) }).
+ */
+export async function readAllLines(filePath: string): Promise<string[]> {
+  if (!existsSync(filePath)) return [];
+  const lines: string[] = [];
+  const rl = createInterface({
+    input: createReadStream(filePath, { encoding: "utf8" }),
+    crlfDelay: Number.POSITIVE_INFINITY,
+  });
+  for await (const line of rl) {
+    lines.push(line);
+  }
+  return lines;
+}
+
+/**
+ * Slice a log line array respecting offset + limit semantics.
+ *
+ * When offset is 0 the function returns the *last* `limit` lines (tail mode).
+ * When offset > 0 it is treated as a 1-based line number and the slice starts
+ * there (for pagination of earlier pages from the tail).
+ *
+ * Returns the selected lines plus metadata used to build the footer.
+ */
+export type LogSlice = {
+  lines: string[];
+  total: number;
+  startLine: number; // 1-based, inclusive
+  endLine: number; // 1-based, inclusive
+  nextOffset: number | null; // null when no previous page exists
+};
+
+export function sliceLogs(allLines: string[], offset: number, limit: number): LogSlice {
+  const total = allLines.length;
+
+  if (total === 0) {
+    return { lines: [], total: 0, startLine: 0, endLine: 0, nextOffset: null };
+  }
+
+  let start: number;
+  if (offset === 0) {
+    // Tail mode: last `limit` lines
+    start = Math.max(0, total - limit);
+  } else {
+    // offset is 1-based line number
+    start = Math.max(0, offset - 1);
+  }
+
+  const end = Math.min(start + limit, total);
+  const lines = allLines.slice(start, end);
+
+  const startLine = start + 1;
+  const endLine = end;
+
+  // nextOffset points to lines *before* current slice (earlier in file)
+  const nextOffset = start > 0 ? Math.max(1, startLine - limit) : null;
+
+  return { lines, total, startLine, endLine, nextOffset };
+}
+
+/**
+ * Build the footer string shown after the log lines.
+ */
+export function buildLogFooter(slice: LogSlice, nArg: number, logPath: string): string {
+  if (slice.total === 0) {
+    return "📭 Log file is empty.\n";
+  }
+
+  const rangeStr = `lines ${slice.startLine}-${slice.endLine} of ${slice.total}`;
+  let footer = `\n📄 ${rangeStr} | ${logPath}\n`;
+
+  if (slice.nextOffset !== null) {
+    footer += `⏩ Earlier lines available. Fetch previous page:\n`;
+    footer += `   nerve logs --offset ${slice.nextOffset} -n ${nArg}\n`;
+  }
+
+  return footer;
+}
+
+// ---------------------------------------------------------------------------
+// nerve logs
+// ---------------------------------------------------------------------------
+
+export const logsCommand = defineCommand({
+  meta: {
+    name: "logs",
+    description: "Show daemon log output",
+  },
+  args: {
+    n: {
+      type: "string",
+      description: `Number of lines to show (default: ${DEFAULT_LOG_LINES})`,
+      default: String(DEFAULT_LOG_LINES),
+    },
+    offset: {
+      type: "string",
+      description: "Start from line N (1-based, for pagination)",
+      default: "0",
+    },
+    follow: {
+      type: "boolean",
+      alias: "f",
+      description: "Stream new log lines in real time",
+      default: false,
+    },
+  },
+  async run({ args }) {
+    const logPath = getLogPath();
+    const nLines = Math.max(1, Number.parseInt(args.n, 10) || DEFAULT_LOG_LINES);
+    const rawOffset = Number.parseInt(args.offset, 10) || 0;
+
+    if (rawOffset < 0) {
+      process.stderr.write(`❌ --offset must be a non-negative integer, got: ${args.offset}\n`);
+      process.exit(1);
+    }
+
+    const offset = rawOffset;
+
+    if (!existsSync(logPath)) {
+      process.stderr.write(`❌ Log file not found: ${logPath}\n`);
+      process.stderr.write("   Has the daemon been started? Try: nerve start\n");
+      process.exit(1);
+    }
+
+    if (args.follow) {
+      await followLog(logPath, nLines);
+      return;
+    }
+
+    const allLines = await readAllLines(logPath);
+    const slice = sliceLogs(allLines, offset, nLines);
+
+    for (const line of slice.lines) {
+      process.stdout.write(`${line}\n`);
+    }
+
+    process.stdout.write(buildLogFooter(slice, nLines, logPath));
+  },
+});
+
+/**
+ * Stream new lines from a log file as they are appended.
+ * Shows the last `tailLines` lines first, then watches for new content.
+ */
+async function followLog(logPath: string, tailLines: number): Promise<void> {
+  const allLines = await readAllLines(logPath);
+  const initial = allLines.slice(Math.max(0, allLines.length - tailLines));
+  for (const line of initial) {
+    process.stdout.write(`${line}\n`);
+  }
+
+  let size = statSync(logPath).size;
+
+  process.stdout.write(`\n👁  Following ${logPath} — press Ctrl+C to stop\n`);
+
+  let stopped = false;
+  process.once("SIGINT", () => {
+    stopped = true;
+  });
+
+  while (!stopped) {
+    await sleep(300);
+    if (stopped) break;
+    try {
+      const newSize = statSync(logPath).size;
+      if (newSize < size) {
+        // Log rotation: file was truncated or replaced, read from the beginning
+        size = 0;
+      }
+      if (newSize <= size) continue;
+
+      const stream = createReadStream(logPath, { start: size, encoding: "utf8" });
+      const rl = createInterface({ input: stream, crlfDelay: Number.POSITIVE_INFINITY });
+      for await (const line of rl) {
+        process.stdout.write(`${line}\n`);
+      }
+      size = newSize;
+    } catch {
+      stopped = true;
+    }
+  }
+}