from __future__ import annotations

import json
import urllib.error
import urllib.request
from typing import Any, Callable


class OllamaError(RuntimeError):
    pass


class OllamaClient:
    def __init__(
        self,
        base_url: str,
        model: str,
        timeout: float = 2.5,
        chat_max_tokens: int | None = None,
    ) -> None:
        self.base_url = base_url.rstrip("/")
        self.model = model
        self.timeout = timeout
        self.chat_max_tokens = chat_max_tokens

    def _chat_system(self, system: str) -> str:
        """Return the application system prompt unchanged."""
        return system

    def _num_predict(self, default: int, *, chat: bool = True) -> int:
        """Qwen3's reasoning commonly needs more than a short-chat token budget."""
        if chat and self.chat_max_tokens is not None:
            return self.chat_max_tokens
        return 1024 if self.model.casefold().startswith("qwen3") else default

    def is_available(self, timeout: float = 0.35) -> bool:
        request = urllib.request.Request(f"{self.base_url}/api/tags", method="GET")
        try:
            with urllib.request.urlopen(request, timeout=timeout) as response:
                return response.status == 200
        except (OSError, urllib.error.URLError, TimeoutError):
            return False

    def list_models(self, timeout: float = 2.0) -> list[str]:
        request = urllib.request.Request(f"{self.base_url}/api/tags", method="GET")
        try:
            with urllib.request.urlopen(request, timeout=timeout) as response:
                payload = json.loads(response.read().decode("utf-8"))
        except (OSError, urllib.error.URLError, TimeoutError, json.JSONDecodeError):
            return []
        return [
            str(model.get("name"))
            for model in payload.get("models", [])
            if isinstance(model, dict) and model.get("name")
        ]

    def generate_json(self, system: str, prompt: str) -> dict[str, Any]:
        raw_response = self._generate(system, prompt, json_format=True)
        try:
            parsed = json.loads(raw_response)
        except (TypeError, json.JSONDecodeError) as exc:
            raise OllamaError("Ollama did not return a valid JSON plan.") from exc
        if not isinstance(parsed, dict):
            raise OllamaError("Ollama returned an unsupported plan shape.")
        return parsed

    def generate_text(self, system: str, prompt: str) -> str:
        response = self._generate(system, prompt, json_format=False).strip()
        if not response:
            raise OllamaError("Ollama returned an empty response.")
        return response

    def generate_text_stream(
        self,
        system: str,
        prompt: str,
        on_chunk: Callable[[str], None],
    ) -> str:
        payload: dict[str, Any] = {
            "model": self.model,
            "system": self._chat_system(system),
            "prompt": prompt,
            "stream": True,
            "options": {"temperature": 0.35, "num_predict": self._num_predict(180)},
        }
        request = urllib.request.Request(
            f"{self.base_url}/api/generate",
            data=json.dumps(payload).encode("utf-8"),
            headers={"Content-Type": "application/json"},
            method="POST",
        )
        pieces: list[str] = []
        try:
            with urllib.request.urlopen(request, timeout=self.timeout) as response:
                for raw_line in response:
                    if not raw_line.strip():
                        continue
                    event = json.loads(raw_line.decode("utf-8"))
                    chunk = str(event.get("response", ""))
                    if chunk:
                        pieces.append(chunk)
                        on_chunk(chunk)
                    if event.get("done"):
                        break
        except (OSError, urllib.error.URLError, json.JSONDecodeError) as exc:
            raise OllamaError(f"Ollama streaming request failed: {exc}") from exc
        result = "".join(pieces).strip()
        if not result:
            raise OllamaError("Ollama returned an empty response.")
        return result

    def _generate(self, system: str, prompt: str, *, json_format: bool) -> str:
        payload: dict[str, Any] = {
            "model": self.model,
            "system": self._chat_system(system),
            "prompt": prompt,
            "stream": False,
            "options": {
                "temperature": 0.1 if json_format else 0.35,
                "num_predict": self._num_predict(300 if json_format else 180, chat=not json_format),
            },
        }
        if json_format:
            payload["format"] = "json"
        body = json.dumps(
            payload
        ).encode("utf-8")
        request = urllib.request.Request(
            f"{self.base_url}/api/generate",
            data=body,
            headers={"Content-Type": "application/json"},
            method="POST",
        )
        try:
            with urllib.request.urlopen(request, timeout=self.timeout) as response:
                payload = json.loads(response.read().decode("utf-8"))
        except urllib.error.HTTPError as exc:
            detail = ""
            try:
                error_payload = json.loads(exc.read().decode("utf-8"))
                detail = str(error_payload.get("error", ""))
            except Exception:
                pass
            raise OllamaError(detail or f"Ollama returned HTTP {exc.code}.") from exc
        except (OSError, urllib.error.URLError, json.JSONDecodeError) as exc:
            raise OllamaError(f"Ollama request failed: {exc}") from exc

        return str(payload.get("response", ""))