"""Streaming response handler — accumulates SSE chunks into a complete Message."""

from collections.abc import AsyncIterator

from rich.live import Live
from rich.markdown import Markdown
from rich.panel import Panel

from app.models.config import DisplayConfig
from app.models.message import Message
from app.models.tool_call import ToolCall, ToolCallFunction
from app.utils.logging import console, get_logger
from app.utils.token_counter import TokenUsage

logger = get_logger(__name__)


class StreamHandler:
    """Processes an SSE chunk stream into a Rich live display and final Message.

    Accumulates content deltas and tool call fragments, renders a live Markdown
    panel during streaming, and produces a complete assistant Message on finish.
    """

    def __init__(self, display_config: DisplayConfig) -> None:
        """Initialize the stream handler.

        Args:
            display_config: Display preferences (streaming toggle, etc.).
        """
        self._display_config = display_config
        self._accumulated_content: str = ""
        self._accumulated_reasoning: str = ""
        self._tool_calls: dict[int, dict[str, str]] = {}
        self._usage: TokenUsage | None = None

    async def process_stream(self, chunk_iter: AsyncIterator[dict]) -> Message:
        """Consume a chunk iterator, rendering live output and returning the final Message.

        Args:
            chunk_iter: Async iterator of parsed SSE chunk dicts.

        Returns:
            Complete assistant Message with accumulated content and tool calls.
        """
        with Live(console=console, refresh_per_second=8) as live:
            async for chunk in chunk_iter:
                self._process_chunk(chunk)

                # Show reasoning while waiting for content
                display_text = self._accumulated_content
                if not display_text and self._accumulated_reasoning:
                    display_text = "*thinking...*"

                if display_text and self._display_config.stream_output:
                    # Render inside the same Assistant panel used for final output
                    # so the live display and final frame are visually consistent
                    live.update(
                        Panel(
                            Markdown(display_text),
                            title="Assistant",
                            border_style="green",
                            expand=True,
                        )
                    )

        tool_calls = self._build_tool_calls() or None
        return Message(
            role="assistant",
            content=self._accumulated_content or None,
            tool_calls=tool_calls,
        )

    def _process_chunk(self, chunk: dict) -> None:
        """Extract content, tool calls, and usage from a single SSE chunk.

        Args:
            chunk: Parsed JSON dict from one SSE data line.
        """
        # Content delta
        choices = chunk.get("choices", [])
        if choices:
            delta = choices[0].get("delta", {})

            content_piece = delta.get("content")
            if content_piece:
                self._accumulated_content += content_piece

            # Reasoning tokens (e.g. qwen3.5 thinking mode)
            reasoning_piece = delta.get("reasoning")
            if reasoning_piece:
                self._accumulated_reasoning += reasoning_piece

            # Tool call deltas (accumulated by index)
            for tc_delta in delta.get("tool_calls", []):
                idx = tc_delta.get("index", 0)
                if idx not in self._tool_calls:
                    self._tool_calls[idx] = {
                        "id": tc_delta.get("id", ""),
                        "name": "",
                        "arguments": "",
                    }
                entry = self._tool_calls[idx]
                if tc_delta.get("id"):
                    entry["id"] = tc_delta["id"]
                func = tc_delta.get("function", {})
                if func.get("name"):
                    entry["name"] += func["name"]
                if func.get("arguments"):
                    entry["arguments"] += func["arguments"]

        # Token usage (typically in the final chunk)
        usage_data = chunk.get("usage")
        if usage_data:
            self._usage = TokenUsage(
                prompt_tokens=usage_data.get("prompt_tokens", 0),
                completion_tokens=usage_data.get("completion_tokens", 0),
                total_tokens=usage_data.get("total_tokens", 0),
            )

    def _build_tool_calls(self) -> list[ToolCall]:
        """Convert accumulated tool call fragments into sorted ToolCall list.

        Returns:
            List of ToolCall objects sorted by stream index.
        """
        if not self._tool_calls:
            return []

        result: list[ToolCall] = []
        for idx in sorted(self._tool_calls):
            entry = self._tool_calls[idx]
            result.append(
                ToolCall(
                    id=entry["id"],
                    type="function",
                    function=ToolCallFunction(
                        name=entry["name"],
                        arguments=entry["arguments"],
                    ),
                )
            )
        return result

    @property
    def usage(self) -> TokenUsage | None:
        """Token usage reported by the API, if available."""
        return self._usage

    def reset(self) -> None:
        """Clear all accumulators for the next turn."""
        self._accumulated_content = ""
        self._accumulated_reasoning = ""
        self._tool_calls.clear()
        self._usage = None