import json
from typing import Any, Generator

from openai import OpenAI

from .tools import Tool, _TOOL_RESULTS_CACHE
from .mcp import MCPClient, load_mcp_tools, load_all_mcp_tools

# ---------------------------------------------------------------------------
# Streaming event contract
# ---------------------------------------------------------------------------
# Each yield from Agent.stream() is a dict with a "type" key:
#
#   {"type": "text",     "content": "partial text"}
#   {"type": "reasoning","content": "model thinking"}
#   {"type": "tool_call", "name": str, "arguments": '{"url":"..."}'}
#   {"type": "tool_output","name": str, "arguments": str, "content": "result", "partial": bool}
#   {"type": "done",     "content": "full assistant response"}
#   {"type": "error",    "content": "error message"}
# ---------------------------------------------------------------------------


class Agent:
    """OpenAI-compatible tool-calling agent with streaming.

    When ``register_final_message_tool()`` is used the model **must** call
    ``final_message`` to signal completion — plain text responses without
    the tool will keep the conversation loop alive.
    """

    def __init__(
        self,
        base_url: str,
        api_key: str,
        model: str,
        max_iterations: int = 150,
        system_prompt: str | None = None,
    ) -> None:
        self.client = OpenAI(base_url=base_url, api_key=api_key)
        self.model = model
        self._tools: list[Tool] = []
        self._final_tool_name: str | None = None
        self._max_iterations = max_iterations
        self.system_prompt = system_prompt

    # ------------------------------------------------------------------
    # Tool registration
    # ------------------------------------------------------------------

    def register_tool(self, *tools: Tool) -> None:
        self._tools.extend(tools)

    def register_mcp(self, url: str, headers: dict[str, str] | None = None) -> list[Tool]:
        """Connect to an MCP server and register all its tools.

        Returns the list of registered Tool instances.
        """
        tools = load_mcp_tools(url=url, headers=headers)
        self._tools.extend(tools)
        return tools

    def register_all_mcp(self) -> dict[str, list[Tool]]:
        """Load tools from all pre-configured MCP servers.

        Returns ``{server_name: [Tool, ...]}`` and registers them.
        """
        all_tools = load_all_mcp_tools()
        for server_tools in all_tools.values():
            self._tools.extend(server_tools)
        return all_tools

    def set_final_message_tool(self, tool_name: str = "final_message") -> None:
        """Set the name of the final message tool for internal handling."""
        self._final_tool_name = tool_name

    # ------------------------------------------------------------------
    # Streaming loop
    # ------------------------------------------------------------------

    def stream(self, messages: list[dict]) -> Generator[dict, None, None]:
        """Yield streaming events until the model calls ``final_message``.

        *messages* is mutated in-place — after the generator completes it
        contains the full conversation history.
        """
        iteration = 0

        # Inject system prompt once at the front if set
        if self.system_prompt and (
            not messages or messages[0].get("role") != "system"
        ):
            messages.insert(0, {"role": "system", "content": self.system_prompt})

        while True:
            iteration += 1
            if iteration > self._max_iterations:
                yield {
                    "type": "error",
                    "content": f"Agent did not call final_message after "
                    f"{self._max_iterations} iterations",
                }
                return

            specs = [t.to_openai_spec() for t in self._tools] if self._tools else None

            collected_content = ""
            collected_tool_calls: dict[int, dict] = {}

            kwargs: dict[str, Any] = dict(
                model=self.model,
                messages=messages,
                stream=True,
                extra_body={"thinking_token_budget": 2000}
            )
            if specs:
                kwargs["tools"] = specs

            try:
                stream = self.client.chat.completions.create(**kwargs)
            except Exception as exc:
                yield {"type": "error", "content": str(exc)}
                return

            for chunk in stream:
                cd = chunk.to_dict()
                choices = cd.get("choices", [])
                if not choices:
                    continue
                delta = choices[0].get("delta", {})

                reasoning = delta.get("reasoning_content") or delta.get("reasoning")
                if reasoning:
                    yield {"type": "reasoning", "content": reasoning}

                # Text content
                content = delta.get("content", "")
                if content:
                    collected_content += content
                    yield {"type": "text", "content": content}

                # Tool call fragments
                for tc in delta.get("tool_calls", []):
                    idx = tc.get("index", 0)
                    if idx not in collected_tool_calls:
                        collected_tool_calls[idx] = {
                            "id": tc.get("id", ""),
                            "function": {"name": "", "arguments": ""},
                        }
                    if tc.get("id"):
                        collected_tool_calls[idx]["id"] = tc["id"]
                    fn = tc.get("function", {})
                    if fn.get("name"):
                        collected_tool_calls[idx]["function"]["name"] += fn["name"]
                    if fn.get("arguments"):
                        collected_tool_calls[idx]["function"]["arguments"] += fn[
                            "arguments"
                        ]

            # --- Handle tool calls ---
            if collected_tool_calls:
                tool_call_list: list[dict[str, Any]] = []
                for idx in sorted(collected_tool_calls.keys()):
                    tc = collected_tool_calls[idx]
                    tool_call_list.append(
                        {
                            "id": tc["id"],
                            "type": "function",
                            "function": {
                                "name": tc["function"]["name"],
                                "arguments": tc["function"]["arguments"],
                            },
                        }
                    )

                # Assistant message with tool_calls (appended before we decide
                # whether to continue or stop so the conversation is coherent)
                assistant_msg: dict[str, Any] = {
                    "role": "assistant",
                    "content": collected_content or None,
                }
                assistant_msg["tool_calls"] = tool_call_list
                messages.append(assistant_msg)

                # --- final_message check (handled internally) ---
                if self._final_tool_name:
                    for tc_spec in tool_call_list:
                        if tc_spec["function"]["name"] == self._final_tool_name:
                            # Dummy tool result so history stays well-formed
                            messages.append(
                                {
                                    "role": "tool",
                                    "tool_call_id": tc_spec["id"],
                                    "content": "",
                                }
                            )
                            messages.append(
                                {"role": "assistant", "content": collected_content}
                            )
                            yield {"type": "done", "content": collected_content}
                            return

                # --- Execute real tools ---
                for tc_spec in tool_call_list:
                    tname = tc_spec["function"]["name"]
                    try:
                        targs = json.loads(tc_spec["function"]["arguments"])
                    except json.JSONDecodeError:
                        targs = {}

                    yield {
                        "type": "tool_call",
                        "name": tname,
                        "arguments": tc_spec["function"]["arguments"],
                    }

                    tool_obj = next(
                        (t for t in self._tools if t.name == tname), None
                    )

                    if tool_obj is None:
                        result_str = f"Error: Tool '{tname}' not found"
                        _TOOL_RESULTS_CACHE[tc_spec["id"]] = result_str
                        yield {
                            "type": "tool_output",
                            "name": tname,
                            "arguments": tc_spec["function"]["arguments"],
                            "content": result_str,
                        }
                        messages.append({
                            "role": "tool",
                            "tool_call_id": tc_spec["id"],
                            "content": result_str,
                        })
                        continue

                    # Streamable tool — yield partial results
                    if tool_obj.streamable:
                        accumulated = ""
                        last_chunk = ""
                        try:
                            for chunk in tool_obj.stream(**targs):
                                accumulated += chunk
                                last_chunk = chunk
                                # Truncate display but keep full for read_tool_response
                                display = accumulated
                                if len(display) > 5_000:
                                    lines = display.split("\n")
                                    char_count = 0
                                    cut_line = 0
                                    for i, line in enumerate(lines):
                                        char_count += len(line) + 1
                                        if char_count > 5_000:
                                            cut_line = i
                                            break
                                    display = "\n".join(lines[:cut_line])
                                yield {
                                    "type": "tool_output",
                                    "name": tname,
                                    "arguments": tc_spec["function"]["arguments"],
                                    "content": display,
                                    "partial": True,
                                }
                            # Mark final yield as non-partial
                            display = accumulated
                            if len(display) > 5_000:
                                lines = display.split("\n")
                                char_count = 0
                                cut_line = 0
                                for i, line in enumerate(lines):
                                    char_count += len(line) + 1
                                    if char_count > 5_000:
                                        cut_line = i
                                        break
                                display = "\n".join(lines[:cut_line])
                            yield {
                                "type": "tool_output",
                                "name": tname,
                                "arguments": tc_spec["function"]["arguments"],
                                "content": display,
                                "partial": False,
                            }
                            result_str = accumulated
                        except Exception as e:
                            result_str = f"Error executing {tname}: {e}"
                    else:
                        # Regular tool — single result
                        try:
                            result_str = str(tool_obj.run(**targs))
                        except Exception as e:
                            result_str = f"Error executing {tname}: {e}"

                    # Store full result and truncate for message history
                    _TOOL_RESULTS_CACHE[tc_spec["id"]] = result_str
                    lines = result_str.split("\n")
                    if len(result_str) > 5_000:
                        char_count = 0
                        cut_line = 0
                        for i, line in enumerate(lines):
                            char_count += len(line) + 1
                            if char_count > 5_000:
                                cut_line = i
                                break
                        truncated = "\n".join(lines[:cut_line])
                        remaining = len(lines) - cut_line
                        result_str = f"{truncated}\n\n...[{remaining} lines truncated — use read_tool_response tool_call_id=\"{tc_spec['id']}\" start_line={cut_line} to read more]"

                    # Final tool_output (non-partial) for history
                    if not tool_obj.streamable:
                        yield {
                            "type": "tool_output",
                            "name": tname,
                            "arguments": tc_spec["function"]["arguments"],
                            "content": result_str,
                        }

                    messages.append({
                        "role": "tool",
                        "tool_call_id": tc_spec["id"],
                        "content": result_str,
                    })

                continue  # Loop back — model can call more tools or final_message

            # --- No tool calls ---
            if self._final_tool_name:
                # final_message is expected but wasn't called — keep the
                # conversation loop alive so the model gets another chance
                messages.append(
                    {"role": "assistant", "content": collected_content}
                )
                continue  # Loop back

            # No final_message tool registered — normal end
            messages.append({"role": "assistant", "content": collected_content})
            yield {"type": "done", "content": collected_content}
            break