"""Model chaining engine for multi-stage AI pipelines."""

from __future__ import annotations

import asyncio
from collections.abc import AsyncIterator
from dataclasses import dataclass
from typing import Any, Callable

from loguru import logger


@dataclass(frozen=True, slots=True)
class ChainStage:
    """A single stage in a model chain."""

    model_ref: str  # e.g., "zen/minimax-m2.5-free"
    stage_name: str  # e.g., "vision_analysis", "code_generation"
    description: str


@dataclass(frozen=True, slots=True)
class ChainResult:
    """Result from executing a chain stage."""

    stage: ChainStage
    output: str
    success: bool
    error: str | None = None


# Chain templates for common multi-capability tasks
CHAIN_TEMPLATES: dict[str, list[ChainStage]] = {
    "vision_to_text": [
        ChainStage(
            model_ref="nvidia_nim/stepfun-ai/step-3.5-flash",
            stage_name="image_analysis",
            description="Analyze image content",
        ),
        ChainStage(
            model_ref="zen/minimax-m2.5-free",
            stage_name="response_generation",
            description="Generate final response",
        ),
    ],
    "reasoning_to_generation": [
        ChainStage(
            model_ref="nvidia_nim/qwen/qwen3-coder-480b-a35b-instruct",
            stage_name="analysis",
            description="Analyze and plan",
        ),
        ChainStage(
            model_ref="zen/minimax-m2.5-free",
            stage_name="generation",
            description="Generate output",
        ),
    ],
}


class ChainEngine:
    """Execute multi-model pipelines for complex requests."""

    def __init__(self, provider_getter: Callable[[str], Any]):
        self._provider_getter = provider_getter

    async def execute_simple_chain(
        self,
        stages: list[ChainStage],
        initial_messages: list[Any],
        system_prompt: str | None = None,
    ) -> AsyncIterator[str]:
        """Execute a chain of models sequentially.

        Args:
            stages: List of chain stages to execute
            initial_messages: Initial user messages
            system_prompt: Optional system prompt

        Yields:
            SSE events from the final model in the chain
        """
        if not stages:
            return

        logger.info("ChainEngine: executing {} stages", len(stages))

        # For now, execute single model - full chaining requires more integration
        # This is a placeholder for the full implementation
        first_stage = stages[0]
        provider = self._provider_getter(first_stage.model_ref.split("/")[0])

        logger.info(
            "ChainEngine: using model {} for chain",
            first_stage.model_ref,
        )

        # For Phase 1, just delegate to provider - full chaining comes later
        # The infrastructure is now in place
        async for event in provider.stream_response(
            initial_messages, system_prompt, {}
        ):
            yield event

    def get_chain_for_requirements(
        self,
        required_capabilities: set[str],
        available_models: list[str],
    ) -> list[ChainStage] | None:
        """Determine the appropriate chain based on required capabilities.

        Args:
            required_capabilities: Set of capabilities needed
            available_models: Available model references

        Returns:
            Chain stages or None if single model is sufficient
        """
        # If only one capability needed, no chain needed
        if len(required_capabilities) <= 1:
            return None

        # If multiple capabilities, build a simple chain
        if "vision" in required_capabilities and "coding" in required_capabilities:
            return CHAIN_TEMPLATES.get("vision_to_text")

        if "vision" in required_capabilities and "reasoning" in required_capabilities:
            return CHAIN_TEMPLATES.get("vision_to_text")

        if "reasoning" in required_capabilities and "coding" in required_capabilities:
            return CHAIN_TEMPLATES.get("reasoning_to_generation")

        # Default: no chain for now
        return None


async def execute_model_for_stage(
    provider: Any,
    messages: list[Any],
    system: str | None,
    metadata: dict[str, Any],
) -> str:
    """Execute a single model stage and return its output."""
    output_parts = []

    try:
        async for event in provider.stream_response(messages, system, metadata):
            # Parse SSE and collect text output
            if "content_block_delta" in event:
                # Extract text from delta
                pass

        return "".join(output_parts)
    except Exception as e:
        logger.error("Chain stage failed: {}", e)
        raise