import { describe, it, expect } from 'bun:test';

/**
 * Tests for SDKAgent resume parameter logic
 *
 * The resume parameter should ONLY be passed when:
 * 1. memorySessionId exists (was captured from a previous SDK response)
 * 2. lastPromptNumber > 1 (this is a continuation within the same SDK session)
 *
 * On worker restart or crash recovery, memorySessionId may exist from a previous
 * SDK session but we must NOT resume because the SDK context was lost.
 */
describe('SDKAgent Resume Parameter Logic', () => {
  /**
   * Helper function that mirrors the logic in SDKAgent.startSession()
   * This is the exact condition used at SDKAgent.ts line 99
   */
  function shouldPassResumeParameter(session: {
    memorySessionId: string | null;
    lastPromptNumber: number;
  }): boolean {
    const hasRealMemorySessionId = !!session.memorySessionId;
    return hasRealMemorySessionId && session.lastPromptNumber > 1;
  }

  describe('INIT prompt scenarios (lastPromptNumber === 1)', () => {
    it('should NOT pass resume parameter when lastPromptNumber === 1 even if memorySessionId exists', () => {
      // Scenario: Worker restart with stale memorySessionId from previous session
      const session = {
        memorySessionId: 'stale-session-id-from-previous-run',
        lastPromptNumber: 1, // INIT prompt
      };

      const hasRealMemorySessionId = !!session.memorySessionId;
      const shouldResume = shouldPassResumeParameter(session);

      expect(hasRealMemorySessionId).toBe(true); // memorySessionId exists
      expect(shouldResume).toBe(false); // but should NOT resume because it's INIT
    });

    it('should NOT pass resume parameter when memorySessionId is null and lastPromptNumber === 1', () => {
      // Scenario: Fresh session, first prompt ever
      const session = {
        memorySessionId: null,
        lastPromptNumber: 1,
      };

      const hasRealMemorySessionId = !!session.memorySessionId;
      const shouldResume = shouldPassResumeParameter(session);

      expect(hasRealMemorySessionId).toBe(false);
      expect(shouldResume).toBe(false);
    });
  });

  describe('CONTINUATION prompt scenarios (lastPromptNumber > 1)', () => {
    it('should pass resume parameter when lastPromptNumber > 1 AND memorySessionId exists', () => {
      // Scenario: Normal continuation within same SDK session
      const session = {
        memorySessionId: 'valid-session-id',
        lastPromptNumber: 2, // CONTINUATION prompt
      };

      const hasRealMemorySessionId = !!session.memorySessionId;
      const shouldResume = shouldPassResumeParameter(session);

      expect(hasRealMemorySessionId).toBe(true);
      expect(shouldResume).toBe(true);
    });

    it('should pass resume parameter for higher prompt numbers', () => {
      // Scenario: Later in a multi-turn conversation
      const session = {
        memorySessionId: 'valid-session-id',
        lastPromptNumber: 5, // 5th prompt in session
      };

      const shouldResume = shouldPassResumeParameter(session);
      expect(shouldResume).toBe(true);
    });

    it('should NOT pass resume parameter when memorySessionId is null even for lastPromptNumber > 1', () => {
      // Scenario: Bug case - somehow got to prompt 2 without capturing memorySessionId
      // This shouldn't happen in practice but we should handle it safely
      const session = {
        memorySessionId: null,
        lastPromptNumber: 2,
      };

      const hasRealMemorySessionId = !!session.memorySessionId;
      const shouldResume = shouldPassResumeParameter(session);

      expect(hasRealMemorySessionId).toBe(false);
      expect(shouldResume).toBe(false);
    });
  });

  describe('Edge cases', () => {
    it('should handle empty string memorySessionId as falsy', () => {
      // Empty string should be treated as "no session ID"
      const session = {
        memorySessionId: '' as unknown as null,
        lastPromptNumber: 2,
      };

      const hasRealMemorySessionId = !!session.memorySessionId;
      const shouldResume = shouldPassResumeParameter(session);

      expect(hasRealMemorySessionId).toBe(false);
      expect(shouldResume).toBe(false);
    });

    it('should handle undefined memorySessionId as falsy', () => {
      const session = {
        memorySessionId: undefined as unknown as null,
        lastPromptNumber: 2,
      };

      const hasRealMemorySessionId = !!session.memorySessionId;
      const shouldResume = shouldPassResumeParameter(session);

      expect(hasRealMemorySessionId).toBe(false);
      expect(shouldResume).toBe(false);
    });
  });

  describe('Bug reproduction: stale session resume crash', () => {
    it('should NOT resume when worker restarts with stale memorySessionId', () => {
      // This is the exact bug scenario from the logs:
      // [17:30:21.773] Starting SDK query {
      //   hasRealMemorySessionId=true,
      //   resume_parameter=5439891b-...,
      //   lastPromptNumber=1              ← NEW SDK session!
      // }
      // [17:30:24.450] Generator failed {error=Claude Code process exited with code 1}

      const session = {
        memorySessionId: '5439891b-7d4b-4ee3-8662-c000f66bc199', // Stale from previous session
        lastPromptNumber: 1, // But this is a NEW session after restart
      };

      const shouldResume = shouldPassResumeParameter(session);

      // The fix: should NOT try to resume, should start fresh
      expect(shouldResume).toBe(false);
    });

    it('should resume correctly for normal continuation (not after restart)', () => {
      // Normal case: same SDK session, continuing conversation
      const session = {
        memorySessionId: '5439891b-7d4b-4ee3-8662-c000f66bc199',
        lastPromptNumber: 2, // Second prompt in SAME session
      };

      const shouldResume = shouldPassResumeParameter(session);

      // Should resume - same session, valid memorySessionId
      expect(shouldResume).toBe(true);
    });
  });
});
