"""
agui.py — AG-UI protocol adapter for Purpose Agent.

Maps PAEvent stream → AG-UI compatible lifecycle/text/tool/state events.
Provides SSE endpoint helper for FastAPI/Starlette integration.

AG-UI event categories:
  - Lifecycle: run_started, run_finished, run_error, agent_started, agent_finished
  - Text: text_delta, text_done
  - Tool: tool_call_start, tool_call_args, tool_call_end
  - State: state_snapshot, state_delta
  - Human: human_input_needed, human_input_received
  - Custom: reasoning_summary, memory_update, skill_update

Bidirectional:
  - Emit events TO the frontend
  - Receive human approval events FROM the frontend
"""
from __future__ import annotations

import json
import time
from dataclasses import dataclass, field
from typing import Any, AsyncIterator

from purpose_agent.runtime.events import PAEvent, EventKind, Visibility

# AG-UI event type mapping
_EVENT_MAP = {
    EventKind.RUN_STARTED: "lifecycle.run_started",
    EventKind.RUN_FINISHED: "lifecycle.run_finished",
    EventKind.RUN_ERROR: "lifecycle.run_error",
    EventKind.AGENT_STARTED: "lifecycle.agent_started",
    EventKind.AGENT_FINISHED: "lifecycle.agent_finished",
    EventKind.AGENT_ERROR: "lifecycle.agent_error",
    EventKind.TEXT_DELTA: "text.delta",
    EventKind.TEXT_DONE: "text.done",
    EventKind.TOOL_STARTED: "tool.call_start",
    EventKind.TOOL_ARGS: "tool.call_args",
    EventKind.TOOL_RESULT: "tool.call_end",
    EventKind.TOOL_ERROR: "tool.call_error",
    EventKind.STATE_SNAPSHOT: "state.snapshot",
    EventKind.STATE_DELTA: "state.delta",
    EventKind.REASONING_SUMMARY: "custom.reasoning",
    EventKind.HUMAN_APPROVAL_REQUESTED: "human.input_needed",
    EventKind.HUMAN_APPROVAL_RECEIVED: "human.input_received",
    EventKind.MEMORY_PROMOTED: "custom.memory_update",
    EventKind.SKILL_UPDATED: "custom.skill_update",
    EventKind.CHECKPOINT_SAVED: "custom.checkpoint",
}


@dataclass
class AGUIEvent:
    """AG-UI formatted event for frontend consumption."""
    type: str
    run_id: str
    lane_id: str = "main"
    timestamp: float = field(default_factory=time.time)
    data: dict[str, Any] = field(default_factory=dict)

    def to_sse(self) -> str:
        """Format as Server-Sent Event."""
        payload = json.dumps(self.to_dict(), default=str)
        return f"data: {payload}\n\n"

    def to_dict(self) -> dict[str, Any]:
        return {
            "type": self.type,
            "runId": self.run_id,
            "laneId": self.lane_id,
            "timestamp": self.timestamp,
            "data": self.data,
        }


class AGUIAdapter:
    """
    Adapter that converts PAEvent stream to AG-UI protocol.
    
    Usage:
        adapter = AGUIAdapter()
        
        # Convert single event
        agui_event = adapter.convert(pa_event)
        
        # Stream conversion (async)
        async for agui_event in adapter.stream(pa_event_iterator):
            yield agui_event.to_sse()
        
        # FastAPI/Starlette SSE endpoint
        @app.get("/stream/{run_id}")
        async def stream(run_id: str):
            return StreamingResponse(
                adapter.sse_generator(event_bus.subscribe(run_id=run_id)),
                media_type="text/event-stream"
            )
    """

    def __init__(self, include_internal: bool = False):
        self._include_internal = include_internal

    def convert(self, event: PAEvent) -> AGUIEvent | None:
        """Convert a single PAEvent to AG-UI format. Returns None for filtered events."""
        # Filter by visibility
        if event.visibility == Visibility.DEBUG:
            return None
        if event.visibility == Visibility.INTERNAL and not self._include_internal:
            return None

        # Safety: reject events with hidden chain-of-thought
        if event.has_hidden_cot():
            return None

        # Map event kind
        agui_type = _EVENT_MAP.get(event.kind)
        if not agui_type:
            agui_type = f"custom.{event.kind.value.replace('.', '_')}"

        return AGUIEvent(
            type=agui_type,
            run_id=event.run_id,
            lane_id=event.lane_id,
            timestamp=event.ts,
            data=event.payload,
        )

    async def stream(self, events: AsyncIterator[PAEvent]) -> AsyncIterator[AGUIEvent]:
        """Convert async PAEvent stream to AG-UI event stream."""
        async for event in events:
            agui = self.convert(event)
            if agui:
                yield agui

    async def sse_generator(self, events: AsyncIterator[PAEvent]) -> AsyncIterator[str]:
        """Generate SSE-formatted strings for HTTP streaming."""
        async for event in events:
            agui = self.convert(event)
            if agui:
                yield agui.to_sse()

    def format_sse_batch(self, events: list[PAEvent]) -> str:
        """Format a batch of events as SSE (for testing/debugging)."""
        lines = []
        for event in events:
            agui = self.convert(event)
            if agui:
                lines.append(agui.to_sse())
        return "".join(lines)