"""Helpers for parsing FastGPT SSE responses."""

from __future__ import annotations

import json
from typing import Any, AsyncIterator, Dict, Iterator, Optional

from .exceptions import StreamParseError
from .stream_types import FastGPTInteractiveEvent, FastGPTStreamEvent


def _infer_interaction_type(payload: Dict[str, Any]) -> str:
    interaction_type = str(payload.get("type") or "").strip()
    if interaction_type in {"userSelect", "userInput"}:
        return interaction_type

    params = payload.get("params") if isinstance(payload.get("params"), dict) else {}
    if isinstance(params.get("inputForm"), list):
        return "userInput"
    if isinstance(params.get("userSelectOptions"), list):
        return "userSelect"
    return "userSelect"


def _normalize_interactive_payload(payload: Dict[str, Any]) -> Dict[str, Any]:
    normalized = payload
    wrapped = normalized.get("interactive")
    if isinstance(wrapped, dict):
        normalized = wrapped

    interaction_type = str(normalized.get("type") or "").strip()
    if interaction_type == "toolChildrenInteractive":
        params = normalized.get("params") if isinstance(normalized.get("params"), dict) else {}
        children_response = params.get("childrenResponse")
        if isinstance(children_response, dict):
            normalized = children_response

    return normalized


def _coerce_line(line: Any) -> str:
    if isinstance(line, bytes):
        return line.decode("utf-8")
    return str(line)


def _build_event(event_name: str, raw_data: str) -> FastGPTStreamEvent:
    normalized_event = event_name or "data"
    if raw_data == "[DONE]":
        return FastGPTStreamEvent(kind="done", raw_event=normalized_event, raw_data=raw_data)

    try:
        payload = json.loads(raw_data) if raw_data else {}
    except json.JSONDecodeError as exc:
        raise StreamParseError(
            f"Failed to parse SSE payload for event '{normalized_event}': {exc}"
        ) from exc

    if normalized_event == "interactive":
        if not isinstance(payload, dict):
            raise StreamParseError(
                f"Expected JSON object payload for event '{normalized_event}', got {type(payload).__name__}"
            )
        normalized_payload = _normalize_interactive_payload(payload)
        if not isinstance(normalized_payload, dict):
            raise StreamParseError(
                f"Expected JSON object payload for event '{normalized_event}', got {type(normalized_payload).__name__}"
            )
        interaction_type = _infer_interaction_type(normalized_payload)
        return FastGPTInteractiveEvent(
            kind="interactive",
            data=normalized_payload,
            raw_event=normalized_event,
            raw_data=raw_data,
            interaction_type=interaction_type,
        )

    allowed_kinds = {
        "data",
        "answer",
        "fastAnswer",
        "flowNodeStatus",
        "flowResponses",
        "toolCall",
        "toolParams",
        "toolResponse",
        "updateVariables",
        "error",
        "done",
    }
    kind = normalized_event if normalized_event in allowed_kinds else "data"
    return FastGPTStreamEvent(kind=kind, data=payload, raw_event=normalized_event, raw_data=raw_data)


def _parse_sse_lines(lines: Iterator[Any]) -> Iterator[FastGPTStreamEvent]:
    current_event: Optional[str] = None
    data_lines: list[str] = []

    def flush() -> Optional[FastGPTStreamEvent]:
        nonlocal current_event, data_lines
        if not current_event and not data_lines:
            return None
        if not data_lines:
            raise StreamParseError(f"Missing data payload for SSE event '{current_event or 'data'}'")
        raw_data = "\n".join(data_lines)
        event = _build_event(current_event or "data", raw_data)
        current_event = None
        data_lines = []
        return event

    for raw_line in lines:
        line = _coerce_line(raw_line).rstrip("\r\n")
        if not line:
            event = flush()
            if event is not None:
                yield event
            continue
        if line.startswith(":"):
            continue
        if line.startswith("event:"):
            if current_event is not None or data_lines:
                raise StreamParseError("Encountered new SSE event before previous event payload was terminated")
            current_event = line[6:].strip() or "data"
            continue
        if line.startswith("data:"):
            data_lines.append(line[5:].strip())
            continue
        raise StreamParseError(f"Unsupported SSE line: {line}")

    event = flush()
    if event is not None:
        yield event


def iter_stream_events(response) -> Iterator[FastGPTStreamEvent]:
    """Yield typed SSE events from a synchronous response stream."""

    yield from _parse_sse_lines(iter(response.iter_lines()))


async def aiter_stream_events(response) -> AsyncIterator[FastGPTStreamEvent]:
    """Yield typed SSE events from an asynchronous response stream."""

    current_event: Optional[str] = None
    data_lines: list[str] = []

    async def flush() -> Optional[FastGPTStreamEvent]:
        nonlocal current_event, data_lines
        if not current_event and not data_lines:
            return None
        if not data_lines:
            raise StreamParseError(f"Missing data payload for SSE event '{current_event or 'data'}'")
        raw_data = "\n".join(data_lines)
        event = _build_event(current_event or "data", raw_data)
        current_event = None
        data_lines = []
        return event

    async for raw_line in response.aiter_lines():
        line = _coerce_line(raw_line).rstrip("\r\n")
        if not line:
            event = await flush()
            if event is not None:
                yield event
            continue
        if line.startswith(":"):
            continue
        if line.startswith("event:"):
            if current_event is not None or data_lines:
                raise StreamParseError("Encountered new SSE event before previous event payload was terminated")
            current_event = line[6:].strip() or "data"
            continue
        if line.startswith("data:"):
            data_lines.append(line[5:].strip())
            continue
        raise StreamParseError(f"Unsupported SSE line: {line}")

    event = await flush()
    if event is not None:
        yield event