"""
Lightweight request tracing for local development.

Captures the full request flow through Tatlock's multi-agent architecture
as structured JSON traces for debugging and optimization.

Enable via DEBUG=true environment variable.

Traces are written to logs/traces/{trace_id}.json
View with logs/traces/viewer.html
"""
from contextlib import asynccontextmanager
from contextvars import ContextVar
from dataclasses import dataclass, field
from datetime import datetime, timezone
from enum import Enum
from pathlib import Path
from typing import Any

import json
import secrets

from src.core.logging_config import get_logger

logger = get_logger(__name__)


class SpanType(str, Enum):
    """Types of traced operations."""
    ROUTER = "router"
    STEWARD = "steward"
    TATLOCK = "tatlock"
    EXPERT = "expert"
    TOOL = "tool"


class SpanStatus(str, Enum):
    """Span completion status."""
    OK = "ok"
    ERROR = "error"


@dataclass
class Span:
    """A single traced operation."""
    span_id: str
    name: str
    type: SpanType
    start_time: datetime
    parent_id: str | None = None
    end_time: datetime | None = None
    status: SpanStatus = SpanStatus.OK
    metadata: dict[str, Any] = field(default_factory=dict)
    details: dict[str, Any] = field(default_factory=dict)
    children: list[str] = field(default_factory=list)
    error: str | None = None

    @property
    def duration_ms(self) -> float | None:
        """Calculate duration in milliseconds."""
        if self.end_time and self.start_time:
            return (self.end_time - self.start_time).total_seconds() * 1000
        return None

    def to_dict(self) -> dict[str, Any]:
        """Convert span to dictionary for JSON serialization."""
        result = {
            "span_id": self.span_id,
            "parent_id": self.parent_id,
            "name": self.name,
            "type": self.type.value,
            "start_time": self.start_time.isoformat(),
            "end_time": self.end_time.isoformat() if self.end_time else None,
            "duration_ms": round(self.duration_ms, 2) if self.duration_ms else None,
            "status": self.status.value,
            "metadata": self.metadata if self.metadata else None,
        }
        # Only include non-empty optional fields
        if self.details:
            result["details"] = self.details
        if self.children:
            result["children"] = self.children
        if self.error:
            result["error"] = self.error
        return {k: v for k, v in result.items() if v is not None}


@dataclass
class Trace:
    """Complete trace of a request."""
    trace_id: str
    conversation_id: str | None
    user: str
    timestamp: datetime
    request: dict[str, Any]
    spans: list[Span] = field(default_factory=list)
    response: dict[str, Any] | None = None
    status: str = "in_progress"

    @property
    def total_duration_ms(self) -> float | None:
        """Calculate total trace duration from span timings."""
        if not self.spans:
            return None
        start = min(s.start_time for s in self.spans)
        ends = [s.end_time for s in self.spans if s.end_time]
        if not ends:
            return None
        end = max(ends)
        return (end - start).total_seconds() * 1000

    def to_dict(self) -> dict[str, Any]:
        """Convert trace to dictionary for JSON serialization."""
        return {
            "trace_id": self.trace_id,
            "conversation_id": self.conversation_id,
            "user": self.user,
            "timestamp": self.timestamp.isoformat(),
            "total_duration_ms": round(self.total_duration_ms, 2) if self.total_duration_ms else None,
            "status": self.status,
            "request": self.request,
            "response": self.response,
            "spans": [s.to_dict() for s in self.spans],
        }


# ContextVar for async-safe trace propagation
_current_trace: ContextVar[Trace | None] = ContextVar("current_trace", default=None)
_current_span: ContextVar[Span | None] = ContextVar("current_span", default=None)


def tracing_enabled() -> bool:
    """Check if tracing is enabled (requires DEBUG=true)."""
    from src.core.config import config
    return config.DEBUG


def _generate_id(prefix: str = "") -> str:
    """Generate unique ID with optional prefix."""
    return f"{prefix}{secrets.token_hex(8)}"


def start_trace(
    conversation_id: str | None,
    user: str,
    request: dict[str, Any],
) -> Trace | None:
    """
    Start a new trace for a request.

    Args:
        conversation_id: Conversation identifier
        user: User identifier
        request: Request data (should include preview and full)

    Returns:
        Trace object if tracing enabled, None otherwise
    """
    if not tracing_enabled():
        return None

    trace = Trace(
        trace_id=_generate_id("trace_"),
        conversation_id=conversation_id,
        user=user,
        timestamp=datetime.now(timezone.utc),
        request=request,
    )
    _current_trace.set(trace)

    logger.debug("trace_started", trace_id=trace.trace_id, user=user)
    return trace


def get_current_trace() -> Trace | None:
    """Get the current trace from context."""
    return _current_trace.get()


def get_current_span() -> Span | None:
    """Get the current span from context."""
    return _current_span.get()


def start_span(
    name: str,
    span_type: SpanType,
    metadata: dict[str, Any] | None = None,
    details: dict[str, Any] | None = None,
) -> Span | None:
    """
    Start a new span within the current trace.

    Args:
        name: Span name (e.g., "steward_analysis")
        span_type: Type of operation
        metadata: Quick-access metadata (shown in timeline)
        details: Expandable details (prompts, full responses)

    Returns:
        Span object if tracing enabled, None otherwise
    """
    trace = get_current_trace()
    if not trace:
        return None

    parent = get_current_span()
    span = Span(
        span_id=_generate_id("span_"),
        name=name,
        type=span_type,
        start_time=datetime.now(timezone.utc),
        parent_id=parent.span_id if parent else None,
        metadata=metadata or {},
        details=details or {},
    )

    # Add to parent's children list
    if parent:
        parent.children.append(span.span_id)

    trace.spans.append(span)
    _current_span.set(span)

    logger.debug(
        "span_started",
        span_id=span.span_id,
        name=name,
        type=span_type.value,
        parent_id=span.parent_id,
    )
    return span


def end_span(
    span: Span | None = None,
    status: SpanStatus = SpanStatus.OK,
    metadata_update: dict[str, Any] | None = None,
    details_update: dict[str, Any] | None = None,
    error: str | None = None,
) -> None:
    """
    End a span and restore parent as current.

    Args:
        span: Span to end (defaults to current span)
        status: Completion status
        metadata_update: Additional metadata to merge
        details_update: Additional details to merge
        error: Error message if failed
    """
    if span is None:
        span = get_current_span()
    if not span:
        return

    span.end_time = datetime.now(timezone.utc)
    span.status = status
    if error:
        span.error = error
        span.status = SpanStatus.ERROR
    if metadata_update:
        span.metadata.update(metadata_update)
    if details_update:
        span.details.update(details_update)

    # Restore parent span as current
    trace = get_current_trace()
    if trace and span.parent_id:
        parent = next((s for s in trace.spans if s.span_id == span.parent_id), None)
        _current_span.set(parent)
    else:
        _current_span.set(None)

    logger.debug(
        "span_ended",
        span_id=span.span_id,
        duration_ms=span.duration_ms,
        status=status.value,
    )


def end_trace(
    response: dict[str, Any] | None = None,
    status: str = "completed",
) -> str | None:
    """
    End the current trace and write to file.

    Args:
        response: Response data to include
        status: Final trace status ("completed" or "error")

    Returns:
        Path to trace file if written, None otherwise
    """
    trace = get_current_trace()
    if not trace:
        return None

    trace.response = response
    trace.status = status

    # Write trace to file
    trace_path = _write_trace(trace)

    # Clear context
    _current_trace.set(None)
    _current_span.set(None)

    logger.info(
        "trace_completed",
        trace_id=trace.trace_id,
        total_duration_ms=round(trace.total_duration_ms, 2) if trace.total_duration_ms else None,
        span_count=len(trace.spans),
        path=str(trace_path) if trace_path else None,
    )

    return str(trace_path) if trace_path else None


def _write_trace(trace: Trace) -> Path | None:
    """Write trace to JSON file."""
    try:
        # Ensure traces directory exists
        traces_dir = Path("logs/traces")
        traces_dir.mkdir(parents=True, exist_ok=True)

        # Write trace file
        trace_path = traces_dir / f"{trace.trace_id}.json"
        with open(trace_path, "w") as f:
            json.dump(trace.to_dict(), f, indent=2, default=str)

        return trace_path

    except Exception as e:
        logger.error("trace_write_failed", error=str(e), trace_id=trace.trace_id)
        return None


@asynccontextmanager
async def trace_span(
    name: str,
    span_type: SpanType,
    metadata: dict[str, Any] | None = None,
    details: dict[str, Any] | None = None,
):
    """
    Async context manager for tracing a span.

    Automatically handles start/end timing and error capture.

    Usage:
        async with trace_span("steward_analysis", SpanType.STEWARD) as span:
            result = await analyze_request(...)
            if span:
                span.metadata["result_count"] = len(result)

    Args:
        name: Span name
        span_type: Type of operation
        metadata: Initial metadata
        details: Initial details (expandable in viewer)

    Yields:
        Span object or None if tracing disabled
    """
    span = start_span(name, span_type, metadata, details)
    try:
        yield span
    except Exception as e:
        end_span(span, SpanStatus.ERROR, error=str(e))
        raise
    else:
        end_span(span, SpanStatus.OK)


def add_tool_spans_from_messages(messages: list[Any], parent_span: Span | None = None) -> None:
    """
    Extract tool calls from PydanticAI result messages and add as child spans.

    Call this after an agent.run() to capture tool-level timing retroactively.
    Note: Since we don't have actual timing, we estimate based on sequence.

    Args:
        messages: List from result.new_messages()
        parent_span: Parent span to attach tool spans to
    """
    trace = get_current_trace()
    if not trace or not parent_span:
        return

    # Import PydanticAI message types
    try:
        from pydantic_ai.messages import ModelRequest, ModelResponse, ToolCallPart, ToolReturnPart
    except ImportError:
        return

    # Track tool calls and their returns
    tool_calls: dict[str, dict[str, Any]] = {}

    for msg in messages:
        if isinstance(msg, ModelResponse):
            for part in msg.parts:
                if isinstance(part, ToolCallPart):
                    tool_calls[part.tool_call_id] = {
                        "name": part.tool_name,
                        "args": part.args if hasattr(part, 'args') else {},
                    }
        elif isinstance(msg, ModelRequest):
            for part in msg.parts:
                if isinstance(part, ToolReturnPart):
                    if part.tool_call_id in tool_calls:
                        tool_info = tool_calls[part.tool_call_id]
                        # Create a span for this tool call
                        span = Span(
                            span_id=_generate_id("span_"),
                            name=tool_info["name"],
                            type=SpanType.TOOL,
                            start_time=parent_span.start_time,  # Approximate
                            end_time=parent_span.end_time or datetime.now(timezone.utc),
                            parent_id=parent_span.span_id,
                            status=SpanStatus.OK,
                            metadata={
                                "tool_name": tool_info["name"],
                                "args_preview": str(tool_info.get("args", {}))[:100],
                            },
                            details={
                                "args": tool_info.get("args", {}),
                                "result": part.content[:2000] if isinstance(part.content, str) else str(part.content)[:2000],
                            },
                        )
                        parent_span.children.append(span.span_id)
                        trace.spans.append(span)