import json
from collections.abc import Iterator

import httpx
from core_domain import ChatCompletionRequestContract, ChatCompletionResponseContract
from core_shared import JSONValue

from app.bootstrap.settings import ModelGatewayServiceSettings


class ModelProviderClientError(Exception):
    pass


class ModelProviderClient:
    def __init__(self, *, settings: ModelGatewayServiceSettings) -> None:
        self.settings = settings

    def create_chat_completion(
        self,
        payload: ChatCompletionRequestContract,
        *,
        provider_type: str | None = None,
        provider_base_url: str | None = None,
        provider_api_key: str | None = None,
        timeout_seconds: float = 60.0,
    ) -> ChatCompletionResponseContract:
        if payload.model is None:
            raise ModelProviderClientError("model is required for chat completion")

        resolved_provider_type = provider_type or self.settings.provider_type
        if resolved_provider_type == "anthropic":
            return self._create_anthropic_message(
                payload,
                provider_base_url=provider_base_url,
                provider_api_key=provider_api_key,
                timeout_seconds=timeout_seconds)

        return self._create_openai_compatible_chat_completion(
            payload,
            provider_base_url=provider_base_url,
            provider_api_key=provider_api_key,
            timeout_seconds=timeout_seconds)

    def stream_chat_completion(
        self,
        payload: ChatCompletionRequestContract,
        *,
        provider_type: str | None = None,
        provider_base_url: str | None = None,
        provider_api_key: str | None = None,
        timeout_seconds: float = 60.0,
    ) -> Iterator[str]:
        if payload.model is None:
            raise ModelProviderClientError("model is required for chat completion")

        resolved_provider_type = provider_type or self.settings.provider_type
        if resolved_provider_type == "anthropic":
            yield from self._stream_anthropic_message(
                payload,
                provider_base_url=provider_base_url,
                provider_api_key=provider_api_key,
                timeout_seconds=timeout_seconds)
            return

        yield from self._stream_openai_compatible_chat_completion(
            payload,
            provider_base_url=provider_base_url,
            provider_api_key=provider_api_key,
            timeout_seconds=timeout_seconds)

    def list_models(
        self,
        *,
        provider_type: str | None = None,
        provider_base_url: str | None = None,
        provider_api_key: str | None = None,
        timeout_seconds: float = 30.0,
    ) -> list[dict[str, JSONValue]]:
        resolved_provider_type = provider_type or self.settings.provider_type
        if resolved_provider_type == "anthropic":
            return self._list_anthropic_models(
                provider_base_url=provider_base_url,
                provider_api_key=provider_api_key,
                timeout_seconds=timeout_seconds)

        return self._list_openai_compatible_models(
            provider_base_url=provider_base_url,
            provider_api_key=provider_api_key,
            timeout_seconds=timeout_seconds)

    def _list_openai_compatible_models(
        self,
        *,
        provider_base_url: str | None,
        provider_api_key: str | None,
        timeout_seconds: float) -> list[dict[str, JSONValue]]:
        request_headers: dict[str, str] = {"content-type": "application/json"}
        api_key = (
            provider_api_key
            if provider_api_key is not None
            else self.settings.provider_api_key
        )
        if api_key:
            request_headers["authorization"] = f"Bearer {api_key}"

        try:
            base_url = provider_base_url or self.settings.provider_base_url
            with httpx.Client(timeout=timeout_seconds) as client:
                response = client.get(_join_url(base_url, "models"), headers=request_headers)
                response.raise_for_status()
        except httpx.HTTPStatusError as exc:
            detail = exc.response.text[:1000]
            raise ModelProviderClientError(
                f"model provider list models failed: {exc.response.status_code} {detail}") from exc
        except httpx.HTTPError as exc:
            raise ModelProviderClientError(f"model provider list models failed: {exc}") from exc

        return _extract_model_items(_coerce_json_dict(response.json()))

    def _list_anthropic_models(
        self,
        *,
        provider_base_url: str | None,
        provider_api_key: str | None,
        timeout_seconds: float) -> list[dict[str, JSONValue]]:
        api_key = (
            provider_api_key
            if provider_api_key is not None
            else self.settings.provider_api_key
        )
        if not api_key:
            raise ModelProviderClientError("anthropic api key is required")

        request_headers = {
            "content-type": "application/json",
            "x-api-key": api_key,
            "anthropic-version": "2023-06-01",
        }

        try:
            base_url = provider_base_url or self.settings.provider_base_url
            with httpx.Client(timeout=timeout_seconds) as client:
                response = client.get(_join_url(base_url, "v1/models"), headers=request_headers)
                response.raise_for_status()
        except httpx.HTTPStatusError as exc:
            detail = exc.response.text[:1000]
            raise ModelProviderClientError(
                f"anthropic list models failed: {exc.response.status_code} {detail}") from exc
        except httpx.HTTPError as exc:
            raise ModelProviderClientError(f"anthropic list models failed: {exc}") from exc

        return _extract_model_items(_coerce_json_dict(response.json()))

    def _create_openai_compatible_chat_completion(
        self,
        payload: ChatCompletionRequestContract,
        *,
        provider_base_url: str | None,
        provider_api_key: str | None,
        timeout_seconds: float) -> ChatCompletionResponseContract:
        request_payload: dict[str, JSONValue] = {
            "model": payload.model or "",
            "messages": [item.model_dump(mode="json") for item in payload.messages],
        }
        if payload.temperature is not None:
            request_payload["temperature"] = payload.temperature
        if payload.max_tokens is not None:
            request_payload["max_tokens"] = payload.max_tokens
        if payload.tools_json:
            request_payload["tools"] = payload.tools_json
        if payload.tool_choice is not None:
            request_payload["tool_choice"] = payload.tool_choice

        request_headers: dict[str, str] = {"content-type": "application/json"}
        api_key = (
            provider_api_key
            if provider_api_key is not None
            else self.settings.provider_api_key
        )
        if api_key:
            request_headers["authorization"] = f"Bearer {api_key}"

        try:
            base_url = provider_base_url or self.settings.provider_base_url
            with httpx.Client(timeout=timeout_seconds) as client:
                response = client.post(
                    _join_url(base_url, "chat/completions"),
                    json=request_payload,
                    headers=request_headers)
                response.raise_for_status()
        except httpx.HTTPStatusError as exc:
            detail = exc.response.text[:1000]
            raise ModelProviderClientError(
                f"model provider request failed: {exc.response.status_code} {detail}") from exc
        except httpx.HTTPError as exc:
            raise ModelProviderClientError(f"model provider request failed: {exc}") from exc

        response_json = _coerce_json_dict(response.json())
        content = _extract_response_content(response_json)
        finish_reason = _extract_finish_reason(response_json)
        tool_calls_json = _extract_tool_calls_json(response_json)
        usage_json = _extract_usage_json(response_json)
        return ChatCompletionResponseContract(
            model=payload.model,
            content=content,
            finish_reason=finish_reason,
            tool_calls_json=tool_calls_json,
            usage_json=usage_json,
            raw_response_json=response_json)

    def _stream_openai_compatible_chat_completion(
        self,
        payload: ChatCompletionRequestContract,
        *,
        provider_base_url: str | None,
        provider_api_key: str | None,
        timeout_seconds: float) -> Iterator[str]:
        request_payload = _build_openai_request_payload(payload)
        request_payload["stream"] = True
        request_headers = _build_openai_headers(
            settings=self.settings,
            provider_api_key=provider_api_key)

        try:
            base_url = provider_base_url or self.settings.provider_base_url
            with httpx.Client(timeout=timeout_seconds) as client:
                with client.stream(
                    "POST",
                    _join_url(base_url, "chat/completions"),
                    json=request_payload,
                    headers=request_headers) as response:
                    response.raise_for_status()
                    for line in response.iter_lines():
                        if not line.startswith("data:"):
                            continue
                        data = line.removeprefix("data:").strip()
                        if data == "[DONE]":
                            break
                        try:
                            payload_json = _coerce_json_dict(json.loads(data))
                        except json.JSONDecodeError:
                            continue
                        delta = _extract_openai_stream_delta(payload_json)
                        if delta:
                            yield delta
        except httpx.HTTPStatusError as exc:
            detail = exc.response.text[:1000]
            raise ModelProviderClientError(
                f"model provider stream failed: {exc.response.status_code} {detail}") from exc
        except httpx.HTTPError as exc:
            raise ModelProviderClientError(f"model provider stream failed: {exc}") from exc

    def _create_anthropic_message(
        self,
        payload: ChatCompletionRequestContract,
        *,
        provider_base_url: str | None,
        provider_api_key: str | None,
        timeout_seconds: float) -> ChatCompletionResponseContract:
        api_key = (
            provider_api_key
            if provider_api_key is not None
            else self.settings.provider_api_key
        )
        if not api_key:
            raise ModelProviderClientError("anthropic api key is required")

        system_prompt, messages = _to_anthropic_messages(payload)
        request_payload: dict[str, JSONValue] = {
            "model": payload.model or "",
            "max_tokens": payload.max_tokens or 1024,
            "messages": messages,
        }
        if system_prompt:
            request_payload["system"] = system_prompt
        if payload.temperature is not None:
            request_payload["temperature"] = payload.temperature

        request_headers = {
            "content-type": "application/json",
            "x-api-key": api_key,
            "anthropic-version": "2023-06-01",
        }

        try:
            base_url = provider_base_url or self.settings.provider_base_url
            with httpx.Client(timeout=timeout_seconds) as client:
                response = client.post(
                    _join_url(base_url, "v1/messages"),
                    json=request_payload,
                    headers=request_headers)
                response.raise_for_status()
        except httpx.HTTPStatusError as exc:
            detail = exc.response.text[:1000]
            raise ModelProviderClientError(
                f"anthropic request failed: {exc.response.status_code} {detail}") from exc
        except httpx.HTTPError as exc:
            raise ModelProviderClientError(f"anthropic request failed: {exc}") from exc

        response_json = _coerce_json_dict(response.json())
        return ChatCompletionResponseContract(
            model=_read_string(response_json, "model") or payload.model,
            content=_extract_anthropic_content(response_json),
            finish_reason=_read_string(response_json, "stop_reason"),
            tool_calls_json=[],
            usage_json=_extract_usage_json(response_json),
            raw_response_json=response_json)

    def _stream_anthropic_message(
        self,
        payload: ChatCompletionRequestContract,
        *,
        provider_base_url: str | None,
        provider_api_key: str | None,
        timeout_seconds: float) -> Iterator[str]:
        api_key = (
            provider_api_key
            if provider_api_key is not None
            else self.settings.provider_api_key
        )
        if not api_key:
            raise ModelProviderClientError("anthropic api key is required")

        system_prompt, messages = _to_anthropic_messages(payload)
        request_payload: dict[str, JSONValue] = {
            "model": payload.model or "",
            "max_tokens": payload.max_tokens or 1024,
            "messages": messages,
            "stream": True,
        }
        if system_prompt:
            request_payload["system"] = system_prompt
        if payload.temperature is not None:
            request_payload["temperature"] = payload.temperature

        request_headers = {
            "content-type": "application/json",
            "x-api-key": api_key,
            "anthropic-version": "2023-06-01",
        }

        try:
            base_url = provider_base_url or self.settings.provider_base_url
            with httpx.Client(timeout=timeout_seconds) as client:
                with client.stream(
                    "POST",
                    _join_url(base_url, "v1/messages"),
                    json=request_payload,
                    headers=request_headers) as response:
                    response.raise_for_status()
                    for line in response.iter_lines():
                        if not line.startswith("data:"):
                            continue
                        data = line.removeprefix("data:").strip()
                        try:
                            payload_json = _coerce_json_dict(json.loads(data))
                        except json.JSONDecodeError:
                            continue
                        delta = _extract_anthropic_stream_delta(payload_json)
                        if delta:
                            yield delta
        except httpx.HTTPStatusError as exc:
            detail = exc.response.text[:1000]
            raise ModelProviderClientError(
                f"anthropic stream failed: {exc.response.status_code} {detail}") from exc
        except httpx.HTTPError as exc:
            raise ModelProviderClientError(f"anthropic stream failed: {exc}") from exc


def _coerce_json_dict(payload: JSONValue) -> dict[str, JSONValue]:
    if isinstance(payload, dict):
        return {str(key): value for key, value in payload.items()}
    return {}


def _build_openai_request_payload(
    payload: ChatCompletionRequestContract) -> dict[str, JSONValue]:
    request_payload: dict[str, JSONValue] = {
        "model": payload.model or "",
        "messages": [item.model_dump(mode="json") for item in payload.messages],
    }
    if payload.temperature is not None:
        request_payload["temperature"] = payload.temperature
    if payload.max_tokens is not None:
        request_payload["max_tokens"] = payload.max_tokens
    if payload.tools_json:
        request_payload["tools"] = payload.tools_json
    if payload.tool_choice is not None:
        request_payload["tool_choice"] = payload.tool_choice
    return request_payload


def _build_openai_headers(
    *,
    settings: ModelGatewayServiceSettings,
    provider_api_key: str | None) -> dict[str, str]:
    request_headers: dict[str, str] = {"content-type": "application/json"}
    api_key = (
        provider_api_key
        if provider_api_key is not None
        else settings.provider_api_key
    )
    if api_key:
        request_headers["authorization"] = f"Bearer {api_key}"
    return request_headers


def _join_url(base_url: str, path: str) -> str:
    normalized_base = base_url.rstrip("/")
    normalized_path = path.strip("/")
    if normalized_path.startswith("v1/") and normalized_base.endswith("/v1"):
        normalized_path = normalized_path.removeprefix("v1/")
    return f"{normalized_base}/{normalized_path}"


def _to_anthropic_messages(
    payload: ChatCompletionRequestContract) -> tuple[str | None, list[dict[str, JSONValue]]]:
    system_parts: list[str] = []
    messages: list[dict[str, JSONValue]] = []
    for message in payload.messages:
        if message.role == "system":
            system_parts.append(message.content)
            continue
        role = "assistant" if message.role == "assistant" else "user"
        if messages and messages[-1].get("role") == role:
            previous = messages[-1].get("content")
            messages[-1]["content"] = f"{previous}\n\n{message.content}" if isinstance(previous, str) else message.content
        else:
            messages.append({"role": role, "content": message.content})
    if not messages:
        messages.append({"role": "user", "content": ""})
    return ("\n\n".join(system_parts) if system_parts else None), messages


def _extract_anthropic_content(payload: dict[str, JSONValue]) -> str:
    content = payload.get("content")
    if isinstance(content, str):
        return content
    if not isinstance(content, list):
        return ""
    parts: list[str] = []
    for item in content:
        if not isinstance(item, dict):
            continue
        text = item.get("text")
        if isinstance(text, str):
            parts.append(text)
    return "\n".join(parts)


def _read_string(payload: dict[str, JSONValue], key: str) -> str | None:
    value = payload.get(key)
    return value if isinstance(value, str) else None


def _extract_model_items(payload: dict[str, JSONValue]) -> list[dict[str, JSONValue]]:
    data = payload.get("data")
    if not isinstance(data, list):
        data = payload.get("models")
    if not isinstance(data, list):
        return []

    items: list[dict[str, JSONValue]] = []
    for item in data:
        if isinstance(item, str):
            model_id = item
            display_name = item
            owned_by = None
        elif isinstance(item, dict):
            model_id = _read_string(item, "id") or _read_string(item, "model") or _read_string(item, "name")
            if model_id is None:
                continue
            display_name = _read_string(item, "display_name") or _read_string(item, "displayName") or model_id
            owned_by = _read_string(item, "owned_by") or _read_string(item, "ownedBy")
        else:
            continue

        model_item: dict[str, JSONValue] = {
            "modelId": model_id,
            "displayName": display_name,
            "modelType": _infer_model_type(model_id),
        }
        if owned_by:
            model_item["ownedBy"] = owned_by
        items.append(model_item)
    return items


def _infer_model_type(model_id: str) -> str:
    normalized = model_id.lower()
    if "embed" in normalized or "embedding" in normalized:
        return "embedding"
    if "rerank" in normalized or "ranker" in normalized:
        return "rerank"
    if "moderation" in normalized:
        return "moderation"
    if "image" in normalized or "vision" in normalized:
        return "image"
    if "audio" in normalized or "whisper" in normalized or "tts" in normalized:
        return "audio"
    if "reason" in normalized or "thinking" in normalized or normalized.endswith("-r1") or "-r1-" in normalized:
        return "reasoning"
    return "chat"


def _extract_response_content(payload: dict[str, JSONValue]) -> str:
    choices = payload.get("choices")
    if isinstance(choices, list) and choices:
        first_choice = choices[0]
        if isinstance(first_choice, dict):
            message = first_choice.get("message")
            if isinstance(message, dict):
                content = message.get("content")
                if isinstance(content, str):
                    return content
            text = first_choice.get("text")
            if isinstance(text, str):
                return text
    return ""


def _extract_openai_stream_delta(payload: dict[str, JSONValue]) -> str:
    choices = payload.get("choices")
    if not isinstance(choices, list) or not choices:
        return ""
    first_choice = choices[0]
    if not isinstance(first_choice, dict):
        return ""
    delta = first_choice.get("delta")
    if isinstance(delta, dict):
        content = delta.get("content")
        if isinstance(content, str):
            return content
    text = first_choice.get("text")
    return text if isinstance(text, str) else ""


def _extract_anthropic_stream_delta(payload: dict[str, JSONValue]) -> str:
    if payload.get("type") != "content_block_delta":
        return ""
    delta = payload.get("delta")
    if not isinstance(delta, dict):
        return ""
    text = delta.get("text")
    return text if isinstance(text, str) else ""


def _extract_finish_reason(payload: dict[str, JSONValue]) -> str | None:
    choices = payload.get("choices")
    if isinstance(choices, list) and choices:
        first_choice = choices[0]
        if isinstance(first_choice, dict):
            finish_reason = first_choice.get("finish_reason")
            if isinstance(finish_reason, str):
                return finish_reason
    return None


def _extract_tool_calls_json(payload: dict[str, JSONValue]) -> list[dict[str, JSONValue]]:
    choices = payload.get("choices")
    if isinstance(choices, list) and choices:
        first_choice = choices[0]
        if isinstance(first_choice, dict):
            message = first_choice.get("message")
            if isinstance(message, dict):
                tool_calls = message.get("tool_calls")
                if isinstance(tool_calls, list):
                    return [
                        {str(item_key): item_value for item_key, item_value in item.items()}
                        for item in tool_calls
                        if isinstance(item, dict)
                    ]
    return []


def _extract_usage_json(payload: dict[str, JSONValue]) -> dict[str, JSONValue]:
    usage = payload.get("usage")
    if isinstance(usage, dict):
        return {str(key): value for key, value in usage.items()}
    return {}