'use strict';

import test from 'node:test';
import assert from 'node:assert/strict';

import {
    TURN_STATES,
    TURN_EVENTS,
    isTurnState,
    nextState,
    statusLabel,
} from '../src/turn-state.js';

// Every state the machine can be in when a delta arrives.
const BUSY_STATES = [
    TURN_STATES.CONNECTING,
    TURN_STATES.THINKING,
    TURN_STATES.WORKING,
    TURN_STATES.STREAMING,
];
const DELTA_EVENTS = [TURN_EVENTS.REASONING, TURN_EVENTS.TOOL_CALL, TURN_EVENTS.CONTENT];

test('the state set is closed and enumerated', () => {
    assert.deepEqual(Object.values(TURN_STATES), [
        'idle', 'connecting', 'thinking', 'working', 'streaming',
    ]);
    for (const state of Object.values(TURN_STATES)) {
        assert.equal(isTurnState(state), true, `${state} is a known state`);
    }
    for (const value of ['', 'thinking…', 'IDLE', null, undefined, 3, {}]) {
        assert.equal(isTurnState(value), false, `${String(value)} is not a state`);
    }
});

test('turn_start always yields connecting, from any state', () => {
    for (const current of Object.values(TURN_STATES)) {
        assert.equal(
            nextState(current, TURN_EVENTS.TURN_START),
            TURN_STATES.CONNECTING,
            `turn_start from ${current}`,
        );
    }
});

test('turn end, cancel, and error always resolve to idle', () => {
    for (const current of Object.values(TURN_STATES)) {
        for (const event of [TURN_EVENTS.TURN_END, TURN_EVENTS.CANCEL, TURN_EVENTS.ERROR]) {
            assert.equal(
                nextState(current, event),
                TURN_STATES.IDLE,
                `${event} from ${current}`,
            );
        }
    }
});

test('each delta kind maps to its state from every state', () => {
    const expected = {
        [TURN_EVENTS.REASONING]: TURN_STATES.THINKING,
        [TURN_EVENTS.TOOL_CALL]: TURN_STATES.WORKING,
        [TURN_EVENTS.CONTENT]: TURN_STATES.STREAMING,
    };
    for (const from of [...BUSY_STATES, TURN_STATES.IDLE]) {
        for (const event of DELTA_EVENTS) {
            assert.equal(
                nextState(from, event),
                expected[event],
                `${event} from ${from}`,
            );
        }
    }
});

test('a later delta moves the state backward, never stalling on the furthest point', () => {
    // Streaming back to thinking, and thinking back to working.
    assert.equal(
        nextState(TURN_STATES.STREAMING, TURN_EVENTS.REASONING),
        TURN_STATES.THINKING,
        'a reasoning delta after content moves back to thinking',
    );
    assert.equal(
        nextState(TURN_STATES.THINKING, TURN_EVENTS.TOOL_CALL),
        TURN_STATES.WORKING,
        'a tool-call delta after reasoning moves back to working',
    );
    assert.equal(
        nextState(TURN_STATES.WORKING, TURN_EVENTS.CONTENT),
        TURN_STATES.STREAMING,
        'content after a tool call moves forward to streaming',
    );
});

test('a repeated delta of the same kind still updates the state', () => {
    for (const event of DELTA_EVENTS) {
        const first = nextState(TURN_STATES.CONNECTING, event);
        const again = nextState(first, event);
        assert.equal(again, first, `${event} is idempotent on its own state`);
    }
});

test('a turn with no reasoning and no tools goes connecting -> streaming', () => {
    let state = nextState(TURN_STATES.IDLE, TURN_EVENTS.TURN_START);
    assert.equal(state, TURN_STATES.CONNECTING);
    for (let i = 0; i < 3; i++) state = nextState(state, TURN_EVENTS.CONTENT);
    assert.equal(state, TURN_STATES.STREAMING);
    state = nextState(state, TURN_EVENTS.TURN_END);
    assert.equal(state, TURN_STATES.IDLE);
});

test('a reasoning-then-tool turn goes connecting -> thinking -> working', () => {
    let state = nextState(TURN_STATES.IDLE, TURN_EVENTS.TURN_START);
    const states = [state];
    for (const event of [TURN_EVENTS.REASONING, TURN_EVENTS.TOOL_CALL, TURN_EVENTS.TURN_END]) {
        state = nextState(state, event);
        states.push(state);
    }
    assert.deepEqual(states, ['connecting', 'thinking', 'working', 'idle']);
});

test('no turn ever begins in a busy state and no delta strands the session', () => {
    for (const terminal of [TURN_EVENTS.TURN_END, TURN_EVENTS.CANCEL, TURN_EVENTS.ERROR]) {
        const state = nextState(TURN_STATES.STREAMING, terminal);
        const restarted = nextState(state, TURN_EVENTS.TURN_START);
        assert.equal(restarted, TURN_STATES.CONNECTING, 'a new turn always starts at connecting');
    }
});

test('the reducer is total: an unknown event never throws and never invents a state', () => {
    for (const current of [...Object.values(TURN_STATES), 'bogus', undefined, null]) {
        for (const event of ['nope', undefined, null, 42]) {
            const next = nextState(current, event);
            assert.equal(isTurnState(next), true, `unknown event keeps a real state`);
        }
    }
    // A known current state survives an unknown event; an invalid one resets.
    assert.equal(nextState(TURN_STATES.WORKING, 'nope'), TURN_STATES.WORKING);
    assert.equal(nextState('bogus', 'nope'), TURN_STATES.IDLE);
});

test('statusLabel names each busy state and leaves idle to the placeholder', () => {
    assert.equal(statusLabel(TURN_STATES.CONNECTING), 'connecting…');
    assert.equal(statusLabel(TURN_STATES.THINKING), 'thinking…');
    assert.equal(statusLabel(TURN_STATES.WORKING), 'working…');
    assert.equal(statusLabel(TURN_STATES.STREAMING), 'streaming…');
    assert.equal(statusLabel(TURN_STATES.IDLE), '', 'idle is not rendered by the spinner');
    assert.equal(statusLabel('bogus'), '', 'an unknown value renders no busy label');
});