import os
import time
import logging
import asyncio
import json
import base64
from datetime import datetime
from typing import AsyncIterator, Literal

import httpx
from dotenv import load_dotenv

from prompts import get_vlm_ocr_prompt

load_dotenv()

# OpenAI-compatible endpoint config
LLM_BASE_URL = os.getenv('LLM_BASE_URL', 'http://localhost:11434/v1/')
LLM_API_KEY = os.getenv('LLM_API_KEY', 'ollama')

# Auth headers for upstream LLM service (OpenAI-compatible Bearer token)
LLM_HEADERS = {'Authorization': f'Bearer {LLM_API_KEY}'}

# Model names (backward compat: fall back to OLLAMA_MODEL if LLM_MODEL not set)
_raw_model = os.getenv('LLM_MODEL') or os.getenv('OLLAMA_MODEL', 'gpt-oss:20b')
LLM_MODEL = _raw_model.strip() if _raw_model else 'gpt-oss:20b'
PRO_LLM_MODEL = os.getenv('PRO_LLM_MODEL', LLM_MODEL)

# VLM for OCR (vision models)
VLM_MODEL = os.getenv('VLM_MODEL', 'qwen3-vl:30b')

# Fallback for legacy OLLAMA_HOST env var (auto-convert to /v1/ path)
_legacy_host = os.getenv('OLLAMA_HOST')
if _legacy_host and not os.getenv('LLM_BASE_URL'):
    base = _legacy_host.rstrip('/')
    if '/v1' not in base:
        LLM_BASE_URL = f"{base}/v1/"

# Normalize trailing slash for base URL
LLM_BASE_URL = LLM_BASE_URL.rstrip('/') + '/'

# Timeouts in seconds (10 minutes for large model loading)
COMPLETION_TIMEOUT = int(os.getenv("LLM_COMPLETION_TIMEOUT", "600"))
OCR_TIMEOUT = int(os.getenv("LLM_OCR_TIMEOUT", "600"))

logger = logging.getLogger('llm')


def _extract_message(response: dict) -> tuple[str, str]:
    """Extract content and thinking from an OpenAI-compatible response dict."""
    choices = response.get('choices', []) if isinstance(response, dict) else []
    msg = (choices[0].get('message', {}) if choices and isinstance(choices, list) else {}).copy()
    content = msg.get('content', '') or ''
    thinking = (msg.get('reasoning_content') or msg.get('thinking', '') or '').strip()
    return content, thinking


def _resolve_system_prompt(system_prompt: str | None) -> str:
    if system_prompt and system_prompt.strip():
        return system_prompt.strip()
    return ''


def _resolve_model_name(model: str | None = None, *, use_pro_model: bool = False) -> str:
    candidate = (model or '').strip()
    if candidate:
        return candidate
    return PRO_LLM_MODEL if use_pro_model else LLM_MODEL


def _build_chat_payload(
    prompt: str,
    *,
    system_prompt: str | None = None,
    temperature: float = 0.7,
    thinking: str | None = None,
    model: str | None = None,
    use_pro_model: bool = False,
    prefill: str | None = None,
) -> dict:
    messages = []
    sys_prompt = _resolve_system_prompt(system_prompt)
    if sys_prompt:
        messages.append({'role': 'system', 'content': sys_prompt})
    messages.append({'role': 'user', 'content': prompt})

    if prefill:
        messages.append({'role': 'assistant', 'content': prefill})

    payload = {
        'model': _resolve_model_name(model, use_pro_model=use_pro_model),
        'messages': messages,
        'stream': False,
    }

    options = {'temperature': temperature}
    if thinking:
        payload['options'] = {'temperature': temperature, 'think': thinking}

    return payload


def _build_chat_stream_payload(
    prompt: str,
    *,
    system_prompt: str | None = None,
    temperature: float = 0.7,
    thinking: str | None = None,
    model: str | None = None,
    use_pro_model: bool = False,
    prefill: str | None = None,
) -> dict:
    messages = []
    sys_prompt = _resolve_system_prompt(system_prompt)
    if sys_prompt:
        messages.append({'role': 'system', 'content': sys_prompt})
    messages.append({'role': 'user', 'content': prompt})

    if prefill:
        messages.append({'role': 'assistant', 'content': prefill})

    payload = {
        'model': _resolve_model_name(model, use_pro_model=use_pro_model),
        'messages': messages,
        'stream': True,
    }

    options = {'temperature': temperature}
    if thinking:
        payload['options'] = {'temperature': temperature, 'think': thinking}

    return payload


def _extract_delta_text(chunk: dict) -> str:
    """Extract text delta from an OpenAI-compatible SSE chunk."""
    choices = chunk.get('choices', []) if isinstance(chunk, dict) else []
    delta = (choices[0].get('delta', {}) if choices and isinstance(choices, list) else {}).copy()
    content = delta.get('content', '') or ''
    return content


def _extract_delta_thinking(chunk: dict) -> str:
    """Extract thinking/reasoning delta from an SSE chunk."""
    choices = chunk.get('choices', []) if isinstance(chunk, dict) else []
    delta = (choices[0].get('delta', {}) if choices and isinstance(choices, list) else {}).copy()
    return (delta.get('reasoning_content') or delta.get('thinking', '') or '').strip()


async def call_ollama(
    prompt: str,
    *,
    system_prompt: str | None = None,
    tag: str = 'default',
    temperature: float = 0.7,
    thinking: str | None = None,
    model: str | None = None,
    use_pro_model: bool = False,
    prefill: str | None = None,
) -> dict:
    """Call OpenAI-compatible chat completions (non-streaming) and return content/thinking."""
    start = time.perf_counter()
    start_dt = datetime.now()

    model_name = _resolve_model_name(model, use_pro_model=use_pro_model)
    log_model_name = 'pro' if (model is None and use_pro_model) else model_name

    logger.info(
        '[LLM][%s] request model=%s base_url=%s prompt_chars=%d system_chars=%d temp=%.2f thinking=%s',
        tag, log_model_name, LLM_BASE_URL, len(prompt),
        len(system_prompt or ''), temperature, thinking,
    )

    payload = _build_chat_payload(
        prompt=prompt, system_prompt=system_prompt, temperature=temperature,
        thinking=thinking, model=model, use_pro_model=use_pro_model, prefill=prefill,
    )

    http_timeout = httpx.Timeout(connect=10.0, read=None, write=30.0, pool=30.0)

    try:
        async with httpx.AsyncClient(base_url=LLM_BASE_URL, headers=LLM_HEADERS, timeout=http_timeout) as client:
            resp = await asyncio.wait_for(
                client.post('/chat/completions', json=payload), timeout=COMPLETION_TIMEOUT,
            )

        resp.raise_for_status()
        response = resp.json()

    except asyncio.CancelledError:
        elapsed_ms = (time.perf_counter() - start) * 1000
        end_dt = datetime.now()

        logger.info(
            '[LLM][%s] call_time [%s --> %s]', tag,
            start_dt.strftime('%H:%M:%S'), end_dt.strftime('%H:%M:%S'),
        )

        logger.warning('[LLM][%s] request cancelled after %.1fms', tag, elapsed_ms)
        raise

    except Exception:
        elapsed_ms = (time.perf_counter() - start) * 1000
        end_dt = datetime.now()

        logger.info(
            '[LLM][%s] call_time [%s --> %s]', tag,
            start_dt.strftime('%H:%M:%S'), end_dt.strftime('%H:%M:%S'),
        )

        logger.exception('[LLM][%s] request failed after %.1fms', tag, elapsed_ms)
        raise

    content, thinking_out = _extract_message(response)

    elapsed_ms = (time.perf_counter() - start) * 1000
    end_dt = datetime.now()

    logger.info(
        '[LLM][%s] call_time [%s --> %s]', tag,
        start_dt.strftime('%H:%M:%S'), end_dt.strftime('%H:%M:%S'),
    )

    logger.info(
        '[LLM][%s] response in %.1fms content_chars=%d thinking_chars=%d',
        tag, elapsed_ms, len(content), len(thinking_out or ''),
    )

    if not content.strip():
        logger.warning('[LLM][%s] empty content returned by model', tag)

    return {'content': content, 'think': thinking_out or ''}


async def stream_ollama(
    prompt: str,
    *,
    system_prompt: str | None = None,
    tag: str = 'default-stream',
    temperature: float = 0.7,
    thinking: str | None = None,
    model: str | None = None,
    use_pro_model: bool = False,
    prefill: str | None = None,
) -> AsyncIterator[str]:
    """Stream text deltas from OpenAI-compatible chat completions."""
    start = time.perf_counter()
    start_dt = datetime.now()

    model_name = _resolve_model_name(model, use_pro_model=use_pro_model)
    log_model_name = 'pro' if (model is None and use_pro_model) else model_name
    yielded_chars = 0

    logger.info(
        '[LLM][%s] stream request model=%s base_url=%s prompt_chars=%d system_chars=%d temp=%.2f thinking=%s',
        tag, log_model_name, LLM_BASE_URL, len(prompt),
        len(system_prompt or ''), temperature, thinking,
    )

    payload = _build_chat_stream_payload(
        prompt=prompt, system_prompt=system_prompt, temperature=temperature,
        thinking=thinking, model=model, use_pro_model=use_pro_model, prefill=prefill,
    )

    http_timeout = httpx.Timeout(connect=10.0, read=None, write=30.0, pool=30.0)

    try:
        async with httpx.AsyncClient(base_url=LLM_BASE_URL, headers=LLM_HEADERS, timeout=http_timeout) as client:
            try:
                async with client.stream('POST', '/chat/completions', json=payload) as response:
                    response.raise_for_status()

                    deadline = time.perf_counter() + COMPLETION_TIMEOUT
                    line_iterator = response.aiter_lines().__aiter__()

                    while True:
                        remaining = deadline - time.perf_counter()
                        if remaining <= 0:
                            raise TimeoutError('LLM stream timed out')

                        try:
                            line = await asyncio.wait_for(line_iterator.__anext__(), timeout=remaining)
                        except StopAsyncIteration:
                            break

                        if not line or line.startswith(':'):
                            continue

                        # SSE data lines: "data: {json}" or "data: [DONE]"
                        if line.startswith('data: '):
                            data_str = line[6:]  # strip "data: " prefix

                        else:
                            data_str = line.strip()

                        if not data_str or data_str == '[DONE]':
                            continue

                        try:
                            chunk = json.loads(data_str)
                        except json.JSONDecodeError:
                            logger.warning('[LLM][%s] ignored invalid stream line', tag)
                            continue

                        if not isinstance(chunk, dict):
                            continue

                        text = _extract_delta_text(chunk)
                        if not text:
                            continue

                        yielded_chars += len(text)
                        yield text

            except asyncio.CancelledError:
                if response is not None:
                    await response.aclose()
                raise

    except asyncio.CancelledError:
        elapsed_ms = (time.perf_counter() - start) * 1000
        end_dt = datetime.now()

        logger.info(
            '[LLM][%s] stream_time [%s --> %s]', tag,
            start_dt.strftime('%H:%M:%S'), end_dt.strftime('%H:%M:%S'),
        )

        logger.warning('[LLM][%s] stream cancelled after %.1fms', tag, elapsed_ms)
        raise

    except Exception:
        elapsed_ms = (time.perf_counter() - start) * 1000
        end_dt = datetime.now()

        logger.info(
            '[LLM][%s] stream_time [%s --> %s]', tag,
            start_dt.strftime('%H:%M:%S'), end_dt.strftime('%H:%M:%S'),
        )

        logger.exception('[LLM][%s] stream failed after %.1fms', tag, elapsed_ms)
        raise

    elapsed_ms = (time.perf_counter() - start) * 1000
    end_dt = datetime.now()

    logger.info(
        '[LLM][%s] stream_time [%s --> %s]', tag,
        start_dt.strftime('%H:%M:%S'), end_dt.strftime('%H:%M:%S'),
    )

    logger.info(
        '[LLM][%s] stream finished in %.1fms yielded_chars=%d',
        tag, elapsed_ms, yielded_chars,
    )


async def stream_ollama_events(
    prompt: str,
    *,
    system_prompt: str | None = None,
    tag: str = 'default-events',
    temperature: float = 0.7,
    thinking: str | None = None,
    model: str | None = None,
    use_pro_model: bool = False,
    enable_thinking: bool = True,
    prefill: str | None = None,
    timeout: float | None = None,
) -> AsyncIterator[tuple[Literal['thinking', 'content'], str]]:
    """Stream (event_type, payload) tuples from OpenAI-compatible chat completions."""
    start = time.perf_counter()
    start_dt = datetime.now()

    model_name = _resolve_model_name(model, use_pro_model=use_pro_model)
    log_model_name = 'pro' if (model is None and use_pro_model) else model_name
    yielded_chars = 0

    logger.info(
        '[LLM][%s] event_stream request model=%s base_url=%s prompt_chars=%d system_chars=%d temp=%.2f thinking=%s',
        tag, log_model_name, LLM_BASE_URL, len(prompt),
        len(system_prompt or ''), temperature, thinking,
    )

    payload = _build_chat_stream_payload(
        prompt=prompt, system_prompt=system_prompt, temperature=temperature,
        thinking=thinking if enable_thinking else None, model=model, use_pro_model=use_pro_model, prefill=prefill,
    )

    effective_timeout = timeout if timeout is not None else COMPLETION_TIMEOUT
    http_timeout = httpx.Timeout(connect=10.0, read=None, write=30.0, pool=30.0)
    sent_thinking = False

    try:
        async with httpx.AsyncClient(base_url=LLM_BASE_URL, headers=LLM_HEADERS, timeout=http_timeout) as client:
            try:
                async with client.stream('POST', '/chat/completions', json=payload) as response:
                    response.raise_for_status()

                    deadline = time.perf_counter() + effective_timeout
                    line_iterator = response.aiter_lines().__aiter__()

                    while True:
                        remaining = deadline - time.perf_counter()
                        if remaining <= 0:
                            raise TimeoutError('LLM event stream timed out')

                        try:
                            line = await asyncio.wait_for(line_iterator.__anext__(), timeout=remaining)
                        except StopAsyncIteration:
                            break

                        if not line or line.startswith(':'):
                            continue

                        # SSE data lines: "data: {json}" or "data: [DONE]"
                        if line.startswith('data: '):
                            data_str = line[6:]  # strip "data: " prefix

                        else:
                            data_str = line.strip()

                        if not data_str or data_str == '[DONE]':
                            continue

                        try:
                            chunk = json.loads(data_str)
                        except json.JSONDecodeError:
                            logger.warning('[LLM][%s] ignored invalid Ollama stream line', tag)
                            continue

                        if not isinstance(chunk, dict):
                            continue

                        error = chunk.get('error')
                        if error:
                            raise RuntimeError(str(error))

                        thinking_delta = _extract_delta_thinking(chunk)
                        if thinking_delta and not sent_thinking:
                            sent_thinking = True
                            yield 'thinking', ''

                        text = _extract_delta_text(chunk)
                        if not text:
                            continue

                        yielded_chars += len(text)
                        yield 'content', text

            except asyncio.CancelledError:
                if response is not None:
                    await response.aclose()
                raise

    except asyncio.CancelledError:
        elapsed_ms = (time.perf_counter() - start) * 1000
        end_dt = datetime.now()

        logger.info(
            '[LLM][%s] event_stream_time [%s --> %s]', tag,
            start_dt.strftime('%H:%M:%S'), end_dt.strftime('%H:%M:%S'),
        )

        logger.warning('[LLM][%s] event stream cancelled after %.1fms', tag, elapsed_ms)
        raise

    except Exception:
        elapsed_ms = (time.perf_counter() - start) * 1000
        end_dt = datetime.now()

        logger.info(
            '[LLM][%s] event_stream_time [%s --> %s]', tag,
            start_dt.strftime('%H:%M:%S'), end_dt.strftime('%H:%M:%S'),
        )

        logger.exception('[LLM][%s] event stream failed after %.1fms', tag, elapsed_ms)
        raise

    elapsed_ms = (time.perf_counter() - start) * 1000
    end_dt = datetime.now()

    logger.info(
        '[LLM][%s] event_stream_time [%s --> %s]', tag,
        start_dt.strftime('%H:%M:%S'), end_dt.strftime('%H:%M:%S'),
    )

    logger.info(
        '[LLM][%s] event stream finished in %.1fms yielded_chars=%d thinking_seen=%s',
        tag, elapsed_ms, yielded_chars, sent_thinking,
    )


async def call_vlm_ocr(image_bytes: bytes, language: str = 'auto') -> str:
    """OCR via VLM using OpenAI-compatible vision API (image_url content part)."""
    start = time.perf_counter()
    start_dt = datetime.now()

    logger.info(
        '[VLM][ocr] request model=%s base_url=%s image_bytes=%d language=%s',
        VLM_MODEL, LLM_BASE_URL, len(image_bytes), language,
    )

    image_b64 = base64.b64encode(image_bytes).decode('ascii')

    payload = {
        'model': VLM_MODEL,
        'messages': [{
            'role': 'user',
            'content': [
                {'type': 'text', 'text': get_vlm_ocr_prompt()},
                {
                    'type': 'image_url',
                    'image_url': {'url': f'data:image/png;base64,{image_b64}'},
                },
            ],
        }],
        'stream': False,
    }

    http_timeout = httpx.Timeout(connect=10.0, read=None, write=30.0, pool=30.0)

    try:
        async with httpx.AsyncClient(base_url=LLM_BASE_URL, headers=LLM_HEADERS, timeout=http_timeout) as client:
            resp = await asyncio.wait_for(
                client.post('/chat/completions', json=payload), timeout=OCR_TIMEOUT,
            )

        resp.raise_for_status()
        response = resp.json()

    except Exception:
        elapsed_ms = (time.perf_counter() - start) * 1000
        end_dt = datetime.now()

        logger.info(
            '[VLM][ocr] call_time [%s --> %s]', start_dt.strftime('%H:%M:%S'),
            end_dt.strftime('%H:%M:%S'),
        )

        logger.exception('[VLM][ocr] request failed after %.1fms', elapsed_ms)
        raise

    content, _ = _extract_message(response)

    elapsed_ms = (time.perf_counter() - start) * 1000
    end_dt = datetime.now()

    logger.info(
        '[VLM][ocr] call_time [%s --> %s]', start_dt.strftime('%H:%M:%S'),
        end_dt.strftime('%H:%M:%S'),
    )

    logger.info(
        '[VLM][ocr] response in %.1fms content_chars=%d', elapsed_ms, len(content),
    )

    if not content.strip():
        logger.warning('[VLM][ocr] empty content returned by model')

    return content