import { describe, it, expect } from 'vitest';
import {
  buildChain,
  appendToChain,
  removeFromChain,
  getNextInChain,
  findChainForTimer,
  getChainPosition,
  hasDownstreamTimers,
  getDownstreamTimerIds,
  getChainTimers,
  CHAIN_PRESETS,
} from './linked-timers';
import type { Timer } from './timer-engine';

function makeTimer(id: string): Timer {
  const now = Date.now();
  return {
    id,
    type: 'countdown',
    label: `Timer ${id}`,
    urgency: 'standard',
    state: 'active',
    targetTime: now + 60_000,
    duration: 60_000,
    createdAt: now,
    startedAt: now,
    pausedAt: null,
    firedAt: null,
    dismissedAt: null,
    completedAt: null,
    elapsedBeforePause: 0,
    cascade: { preset: 'none', intervals: [] },
    warnings: [],
    snoozeCount: 0,
    snoozedUntil: null,
  };
}

describe('buildChain', () => {
  it('creates a chain with correct links', () => {
    const chain = buildChain('Test', ['a', 'b', 'c']);
    expect(chain.name).toBe('Test');
    expect(chain.timerIds).toEqual(['a', 'b', 'c']);
    expect(chain.links).toHaveLength(2);
    expect(chain.links[0]).toEqual({ fromId: 'a', toId: 'b', delay: 0 });
    expect(chain.links[1]).toEqual({ fromId: 'b', toId: 'c', delay: 0 });
  });

  it('creates a chain with custom delay', () => {
    const chain = buildChain('Delayed', ['x', 'y'], 5000);
    expect(chain.links[0].delay).toBe(5000);
  });

  it('handles single timer (no links)', () => {
    const chain = buildChain('Solo', ['a']);
    expect(chain.timerIds).toEqual(['a']);
    expect(chain.links).toHaveLength(0);
  });

  it('handles empty timer list', () => {
    const chain = buildChain('Empty', []);
    expect(chain.timerIds).toEqual([]);
    expect(chain.links).toHaveLength(0);
  });
});

describe('appendToChain', () => {
  it('appends a timer to end of chain', () => {
    const chain = buildChain('Base', ['a', 'b']);
    const extended = appendToChain(chain, 'c', 1000);
    expect(extended.timerIds).toEqual(['a', 'b', 'c']);
    expect(extended.links).toHaveLength(2);
    expect(extended.links[1]).toEqual({ fromId: 'b', toId: 'c', delay: 1000 });
  });

  it('preserves existing links', () => {
    const chain = buildChain('Base', ['a', 'b'], 500);
    const extended = appendToChain(chain, 'c');
    expect(extended.links[0].delay).toBe(500);
    expect(extended.links[1].delay).toBe(0);
  });
});

describe('removeFromChain', () => {
  it('removes a middle timer and relinks', () => {
    const chain = buildChain('Test', ['a', 'b', 'c']);
    const reduced = removeFromChain(chain, 'b');
    expect(reduced.timerIds).toEqual(['a', 'c']);
    expect(reduced.links).toHaveLength(1);
    expect(reduced.links[0].fromId).toBe('a');
    expect(reduced.links[0].toId).toBe('c');
  });

  it('removes first timer', () => {
    const chain = buildChain('Test', ['a', 'b', 'c']);
    const reduced = removeFromChain(chain, 'a');
    expect(reduced.timerIds).toEqual(['b', 'c']);
    expect(reduced.links).toHaveLength(1);
  });

  it('removes last timer', () => {
    const chain = buildChain('Test', ['a', 'b', 'c']);
    const reduced = removeFromChain(chain, 'c');
    expect(reduced.timerIds).toEqual(['a', 'b']);
    expect(reduced.links).toHaveLength(1);
  });

  it('returns unchanged if timer not in chain', () => {
    const chain = buildChain('Test', ['a', 'b']);
    const same = removeFromChain(chain, 'z');
    expect(same.timerIds).toEqual(['a', 'b']);
  });
});

describe('getNextInChain', () => {
  it('finds the next link after a completed timer', () => {
    const chain = buildChain('Test', ['a', 'b', 'c']);
    const link = getNextInChain([chain], 'a');
    expect(link).not.toBeNull();
    expect(link!.toId).toBe('b');
  });

  it('returns null for last timer in chain', () => {
    const chain = buildChain('Test', ['a', 'b']);
    const link = getNextInChain([chain], 'b');
    expect(link).toBeNull();
  });

  it('returns null for unknown timer', () => {
    const chain = buildChain('Test', ['a', 'b']);
    const link = getNextInChain([chain], 'z');
    expect(link).toBeNull();
  });

  it('searches across multiple chains', () => {
    const c1 = buildChain('Chain1', ['a', 'b']);
    const c2 = buildChain('Chain2', ['x', 'y']);
    const link = getNextInChain([c1, c2], 'x');
    expect(link!.toId).toBe('y');
  });
});

describe('findChainForTimer', () => {
  it('finds the chain containing a timer', () => {
    const c1 = buildChain('C1', ['a', 'b']);
    const c2 = buildChain('C2', ['x', 'y']);
    const found = findChainForTimer([c1, c2], 'x');
    expect(found!.name).toBe('C2');
  });

  it('returns null if not found', () => {
    const chain = buildChain('C1', ['a', 'b']);
    expect(findChainForTimer([chain], 'z')).toBeNull();
  });
});

describe('getChainPosition', () => {
  it('returns correct position', () => {
    const chain = buildChain('Test', ['a', 'b', 'c']);
    const pos = getChainPosition([chain], 'b');
    expect(pos!.index).toBe(1);
    expect(pos!.total).toBe(3);
  });

  it('returns null for unknown timer', () => {
    const chain = buildChain('Test', ['a']);
    expect(getChainPosition([chain], 'z')).toBeNull();
  });
});

describe('hasDownstreamTimers', () => {
  it('returns true for non-last timer', () => {
    const chain = buildChain('Test', ['a', 'b', 'c']);
    expect(hasDownstreamTimers([chain], 'a')).toBe(true);
    expect(hasDownstreamTimers([chain], 'b')).toBe(true);
  });

  it('returns false for last timer', () => {
    const chain = buildChain('Test', ['a', 'b']);
    expect(hasDownstreamTimers([chain], 'b')).toBe(false);
  });

  it('returns false for unknown timer', () => {
    const chain = buildChain('Test', ['a']);
    expect(hasDownstreamTimers([chain], 'z')).toBe(false);
  });
});

describe('getDownstreamTimerIds', () => {
  it('returns downstream IDs', () => {
    const chain = buildChain('Test', ['a', 'b', 'c', 'd']);
    expect(getDownstreamTimerIds([chain], 'b')).toEqual(['c', 'd']);
  });

  it('returns empty for last timer', () => {
    const chain = buildChain('Test', ['a', 'b']);
    expect(getDownstreamTimerIds([chain], 'b')).toEqual([]);
  });
});

describe('getChainTimers', () => {
  it('resolves timer objects', () => {
    const timers = [makeTimer('a'), makeTimer('b'), makeTimer('c')];
    const chain = buildChain('Test', ['a', 'b', 'c']);
    const resolved = getChainTimers(chain, timers);
    expect(resolved).toHaveLength(3);
    expect(resolved[0]!.id).toBe('a');
    expect(resolved[2]!.id).toBe('c');
  });

  it('returns null for missing timers', () => {
    const timers = [makeTimer('a')];
    const chain = buildChain('Test', ['a', 'missing']);
    const resolved = getChainTimers(chain, timers);
    expect(resolved[0]!.id).toBe('a');
    expect(resolved[1]).toBeNull();
  });
});

describe('CHAIN_PRESETS', () => {
  it('has at least 3 presets', () => {
    expect(CHAIN_PRESETS.length).toBeGreaterThanOrEqual(3);
  });

  it('each preset has steps with durations', () => {
    for (const preset of CHAIN_PRESETS) {
      expect(preset.name).toBeTruthy();
      expect(preset.steps.length).toBeGreaterThan(0);
      for (const step of preset.steps) {
        expect(step.label).toBeTruthy();
        expect(step.durationMs).toBeGreaterThan(0);
      }
    }
  });
});