import { Platform } from 'react-native';
import {
    buildBaseUrl,
    chatCompletion,
    chatCompletionStream,
    getModels,
    parseSSELines,
    testConnection,
} from '../services/lmStudioApi';
import { ServerConfig } from '../services/types';

const config: ServerConfig = { host: '192.168.0.10', port: 1234 };

const fetchMock = jest.fn();
const originalFetch = global.fetch;

beforeEach(() => {
    fetchMock.mockReset();
    global.fetch = fetchMock as unknown as typeof fetch;
});

afterAll(() => {
    global.fetch = originalFetch;
});

const sseLine = (content: string) => `data: ${JSON.stringify({ choices: [{ delta: { content } }] })}`;

describe('buildBaseUrl', () => {
    it('prepends http:// and appends port and /v1', () => {
        expect(buildBaseUrl(config)).toBe('http://192.168.0.10:1234/v1');
    });

    it('keeps an explicit http or https scheme', () => {
        expect(buildBaseUrl({ host: 'http://lan.local', port: 8080 })).toBe('http://lan.local:8080/v1');
        expect(buildBaseUrl({ host: 'https://lan.local', port: 443 })).toBe('https://lan.local:443/v1');
    });

    it('strips trailing slashes from the host', () => {
        expect(buildBaseUrl({ host: 'http://lan.local//', port: 1234 })).toBe('http://lan.local:1234/v1');
    });

    it('does not mistake a host that merely starts with "http" for a scheme', () => {
        expect(buildBaseUrl({ host: 'httpbin.local', port: 1234 })).toBe('http://httpbin.local:1234/v1');
    });
});

describe('parseSSELines', () => {
    it('emits content of every complete data line and keeps the partial tail', () => {
        const onChunk = jest.fn();
        const onDone = jest.fn();
        const result = parseSSELines(`${sseLine('Hel')}\n${sseLine('lo')}\ndata: {"cho`, onChunk, onDone);

        expect(onChunk.mock.calls).toEqual([['Hel'], ['lo']]);
        expect(result).toEqual({ remaining: 'data: {"cho', isDone: false });
        expect(onDone).not.toHaveBeenCalled();
    });

    it('stops at [DONE] and calls onDone', () => {
        const onChunk = jest.fn();
        const onDone = jest.fn();
        const result = parseSSELines(`${sseLine('a')}\ndata: [DONE]\n${sseLine('ignored')}\n`, onChunk, onDone);

        expect(onChunk.mock.calls).toEqual([['a']]);
        expect(onDone).toHaveBeenCalledTimes(1);
        expect(result).toEqual({ remaining: '', isDone: true });
    });

    it('skips malformed JSON, empty deltas, comments and non-data lines', () => {
        const onChunk = jest.fn();
        parseSSELines(
            [
                'data: {not json}',
                'data: {"choices":[{"delta":{}}]}',
                'data: {"choices":[]}',
                ': keep-alive',
                'event: message',
                '',
                sseLine('ok'),
                '',
            ].join('\n'),
            onChunk,
            jest.fn(),
        );
        expect(onChunk.mock.calls).toEqual([['ok']]);
    });

    it('handles CRLF line endings and "data:" without a space', () => {
        const onChunk = jest.fn();
        const noSpace = `data:${JSON.stringify({ choices: [{ delta: { content: 'nospace' } }] })}`;
        parseSSELines(`${sseLine('crlf')}\r\n${noSpace}\n`, onChunk, jest.fn());
        expect(onChunk.mock.calls).toEqual([['crlf'], ['nospace']]);
    });
});

describe('testConnection', () => {
    it('sends the Authorization header only when an API key is set', async () => {
        fetchMock.mockResolvedValue({ ok: true });
        await testConnection({ ...config, apiKey: 'secret' });
        await testConnection({ ...config, apiKey: '' });

        expect(fetchMock.mock.calls[0][0]).toBe('http://192.168.0.10:1234/v1/models');
        expect(fetchMock.mock.calls[0][1].headers).toMatchObject({ Authorization: 'Bearer secret' });
        expect(fetchMock.mock.calls[1][1].headers).not.toHaveProperty('Authorization');
    });

    it('returns true on a 2xx response and false otherwise', async () => {
        fetchMock.mockResolvedValueOnce({ ok: true });
        await expect(testConnection(config)).resolves.toBe(true);
        fetchMock.mockResolvedValueOnce({ ok: false });
        await expect(testConnection(config)).resolves.toBe(false);
    });

    it('returns false when the network call throws', async () => {
        fetchMock.mockRejectedValue(new TypeError('Network request failed'));
        await expect(testConnection(config)).resolves.toBe(false);
    });

    it('aborts after 5 seconds and returns false', async () => {
        jest.useFakeTimers();
        try {
            fetchMock.mockImplementation(
                (_url: string, init: { signal: AbortSignal }) =>
                    new Promise((_resolve, reject) => {
                        init.signal.addEventListener('abort', () => reject(new Error('aborted')));
                    }),
            );
            const pending = testConnection(config);
            await jest.advanceTimersByTimeAsync(5000);
            await expect(pending).resolves.toBe(false);
        } finally {
            jest.useRealTimers();
        }
    });

    it('does not leave the timeout timer running after a failure', async () => {
        jest.useFakeTimers();
        try {
            fetchMock.mockRejectedValue(new TypeError('Network request failed'));
            await testConnection(config);
            expect(jest.getTimerCount()).toBe(0);
        } finally {
            jest.useRealTimers();
        }
    });
});

describe('getModels', () => {
    it('returns the data array', async () => {
        fetchMock.mockResolvedValue({ ok: true, json: async () => ({ data: [{ id: 'm1' }] }) });
        await expect(getModels(config)).resolves.toEqual([{ id: 'm1' }]);
    });

    it('falls back to an empty list when data is missing', async () => {
        fetchMock.mockResolvedValue({ ok: true, json: async () => ({}) });
        await expect(getModels(config)).resolves.toEqual([]);
    });

    it('throws with the HTTP status when the response is not ok', async () => {
        fetchMock.mockResolvedValue({ ok: false, status: 401, statusText: 'Unauthorized' });
        await expect(getModels(config)).rejects.toThrow('Failed to fetch models: 401 Unauthorized');
    });
});

describe('chatCompletion', () => {
    it('posts a non-streaming request with defaults that options can override', async () => {
        fetchMock.mockResolvedValue({ ok: true, json: async () => ({ id: 'x' }) });
        await chatCompletion(config, 'model-a', [{ role: 'user', content: 'hi' }], { temperature: 0.1 });

        const [url, init] = fetchMock.mock.calls[0];
        expect(url).toBe('http://192.168.0.10:1234/v1/chat/completions');
        expect(init.method).toBe('POST');
        expect(JSON.parse(init.body)).toEqual({
            model: 'model-a',
            messages: [{ role: 'user', content: 'hi' }],
            stream: false,
            temperature: 0.1,
            max_tokens: 2048,
        });
    });

    it('throws with the HTTP status when the response is not ok', async () => {
        fetchMock.mockResolvedValue({ ok: false, status: 500, statusText: 'Server Error' });
        await expect(chatCompletion(config, 'm', [])).rejects.toThrow('Chat completion failed: 500 Server Error');
    });
});

describe('chatCompletionStream (web, fetch + ReadableStream)', () => {
    const originalOS = Platform.OS;
    const encoder = new TextEncoder();

    beforeEach(() => {
        Platform.OS = 'web';
    });
    afterEach(() => {
        Platform.OS = originalOS;
    });

    const streamOf = (parts: string[]) =>
        new ReadableStream<Uint8Array>({
            start(controller) {
                parts.forEach((p) => controller.enqueue(encoder.encode(p)));
                controller.close();
            },
        });

    // Starts a stream and resolves once either onDone or onError fired.
    const run = () => {
        const onChunk = jest.fn();
        const onDone = jest.fn();
        const onError = jest.fn();
        const finished = new Promise<void>((resolve) => {
            chatCompletionStream(
                config,
                'm',
                [],
                onChunk,
                () => {
                    onDone();
                    resolve();
                },
                (e) => {
                    onError(e);
                    resolve();
                },
            );
        });
        return { onChunk, onDone, onError, finished };
    };

    it('streams chunks split across reads and calls onDone exactly once', async () => {
        const whole = `${sseLine('Hi')}\n${sseLine(' there')}\ndata: [DONE]\n`;
        fetchMock.mockResolvedValue({ ok: true, body: streamOf([whole.slice(0, 20), whole.slice(20)]) });

        const { onChunk, onDone, onError, finished } = run();
        await finished;

        expect(onChunk.mock.calls).toEqual([['Hi'], [' there']]);
        expect(onDone).toHaveBeenCalledTimes(1);
        expect(onError).not.toHaveBeenCalled();
        expect(JSON.parse(fetchMock.mock.calls[0][1].body).stream).toBe(true);
    });

    it('calls onDone when the stream ends without [DONE]', async () => {
        fetchMock.mockResolvedValue({ ok: true, body: streamOf([`${sseLine('x')}\n`]) });
        const { onChunk, onDone, finished } = run();
        await finished;
        expect(onChunk).toHaveBeenCalledWith('x');
        expect(onDone).toHaveBeenCalledTimes(1);
    });

    it('reports an HTTP error through onError', async () => {
        fetchMock.mockResolvedValue({ ok: false, status: 404, statusText: 'Not Found' });
        const { onError, finished } = run();
        await finished;
        expect(onError.mock.calls[0][0].message).toBe('Stream failed: 404 Not Found');
    });

    it('turns a network failure into an actionable connection error', async () => {
        fetchMock.mockRejectedValue(new TypeError('Failed to fetch'));
        const { onError, finished } = run();
        await finished;
        expect(onError.mock.calls[0][0].message).toContain('Could not reach the server at http://192.168.0.10:1234/v1');
    });

    it('does not report an error when the request is aborted', async () => {
        fetchMock.mockImplementation(
            (_url: string, init: { signal: AbortSignal }) =>
                new Promise((_resolve, reject) => {
                    init.signal.addEventListener('abort', () => {
                        const err = new Error('aborted');
                        err.name = 'AbortError';
                        reject(err);
                    });
                }),
        );
        const onError = jest.fn();
        const handle = chatCompletionStream(config, 'm', [], jest.fn(), jest.fn(), onError);
        handle.abort();
        await new Promise((r) => setTimeout(r, 0));
        expect(onError).not.toHaveBeenCalled();
    });
});

describe('chatCompletionStream (native, XMLHttpRequest)', () => {
    class FakeXHR {
        static last: FakeXHR;
        status = 200;
        statusText = 'OK';
        responseText = '';
        headers: Record<string, string> = {};
        aborted = false;
        onprogress: (() => void) | null = null;
        onload: (() => void) | null = null;
        onerror: (() => void) | null = null;
        ontimeout: (() => void) | null = null;
        open = jest.fn();
        send = jest.fn();
        constructor() {
            FakeXHR.last = this;
        }
        setRequestHeader(k: string, v: string) {
            this.headers[k] = v;
        }
        abort() {
            this.aborted = true;
        }
    }

    const originalXHR = global.XMLHttpRequest;
    beforeEach(() => {
        global.XMLHttpRequest = FakeXHR as unknown as typeof XMLHttpRequest;
    });
    afterEach(() => {
        global.XMLHttpRequest = originalXHR;
    });

    it('parses progress events incrementally and finishes once', () => {
        const onChunk = jest.fn();
        const onDone = jest.fn();
        chatCompletionStream({ ...config, apiKey: 'k' }, 'm', [], onChunk, onDone, jest.fn());
        const xhr = FakeXHR.last;

        expect(xhr.open).toHaveBeenCalledWith('POST', 'http://192.168.0.10:1234/v1/chat/completions');
        expect(xhr.headers.Authorization).toBe('Bearer k');

        const full = `${sseLine('A')}\n${sseLine('B')}\n`;
        xhr.responseText = full.slice(0, 30);
        xhr.onprogress?.();
        xhr.responseText = full;
        xhr.onprogress?.();
        xhr.responseText = `${full}data: [DONE]\n`;
        xhr.onprogress?.();
        xhr.onload?.();

        expect(onChunk.mock.calls).toEqual([['A'], ['B']]);
        expect(onDone).toHaveBeenCalledTimes(1);
    });

    it('flushes a final line that has no trailing newline on load', () => {
        const onChunk = jest.fn();
        chatCompletionStream(config, 'm', [], onChunk, jest.fn(), jest.fn());
        const xhr = FakeXHR.last;
        xhr.responseText = sseLine('tail');
        xhr.onprogress?.();
        xhr.onload?.();
        expect(onChunk.mock.calls).toEqual([['tail']]);
    });

    it('reports an HTTP error status instead of finishing silently', () => {
        const onDone = jest.fn();
        const onError = jest.fn();
        chatCompletionStream(config, 'm', [], jest.fn(), onDone, onError);
        const xhr = FakeXHR.last;
        xhr.status = 401;
        xhr.statusText = 'Unauthorized';
        xhr.responseText = '{"error":"bad key"}';
        xhr.onprogress?.();
        xhr.onload?.();

        expect(onError.mock.calls[0][0].message).toBe('Stream failed: 401 Unauthorized');
        expect(onDone).not.toHaveBeenCalled();
    });

    it('turns a network error into an actionable connection error', () => {
        const onError = jest.fn();
        chatCompletionStream(config, 'm', [], jest.fn(), jest.fn(), onError);
        FakeXHR.last.status = 0;
        FakeXHR.last.onerror?.();
        expect(onError.mock.calls[0][0].message).toContain('Could not reach the server at http://192.168.0.10:1234/v1');
    });

    it('reports a timeout', () => {
        const onError = jest.fn();
        chatCompletionStream(config, 'm', [], jest.fn(), jest.fn(), onError);
        FakeXHR.last.ontimeout?.();
        expect(onError.mock.calls[0][0].message).toBe('Request timed out');
    });

    it('abort() aborts the request and swallows errors thrown by abort', () => {
        const handle = chatCompletionStream(config, 'm', [], jest.fn(), jest.fn(), jest.fn());
        const xhr = FakeXHR.last;
        handle.abort();
        expect(xhr.aborted).toBe(true);

        xhr.abort = () => {
            throw new Error('boom');
        };
        expect(() => handle.abort()).not.toThrow();
    });
});