"""
Asyncio-based YAML LSP WebSocket proxy.

Architecture:
  Editor (WebSocket) ──► YamlWsProxy ──► yaml-language-server (TCP:YAML_LSP_PORT)

Intercepts:
  - textDocument/didOpen + didChange  → tracks document content per URI
  - textDocument/completion requests  → detects template context (AzDO / GHA)
  - textDocument/completion responses → injects pipeline template completions

Context detection:
  AzDO: scan back for '- template: PATH@ALIAS', cursor in 'parameters:' block
  GHA:  scan back for 'uses: ORG/REPO/.github/workflows/FILE@REF', cursor in 'with:' block
"""

import asyncio
import json
import logging
import re
from typing import Any

from aiohttp import web, WSMsgType

from .catalog import PipelineTemplateCatalog

logger = logging.getLogger(__name__)

_CHUNK = 65536


# ── LSP framing ────────────────────────────────────────────────────────────────


class _LspFrameBuffer:
    """Reassembles LSP Content-Length framed messages from a stream of bytes."""

    def __init__(self) -> None:
        self._buf = b""

    def feed(self, data: bytes) -> list[bytes]:
        """Feed bytes and return complete frames (as raw bytes, without header)."""
        self._buf += data
        frames = []
        while True:
            sep = self._buf.find(b"\r\n\r\n")
            if sep == -1:
                break
            header = self._buf[:sep]
            length = 0
            for part in header.split(b"\r\n"):
                if part.lower().startswith(b"content-length:"):
                    length = int(part.split(b":")[1].strip())
            body_start = sep + 4
            if len(self._buf) < body_start + length:
                break
            frames.append(self._buf[body_start : body_start + length])
            self._buf = self._buf[body_start + length :]
        return frames


def _lsp_frame(body: bytes) -> bytes:
    return f"Content-Length: {len(body)}\r\n\r\n".encode() + body


# ── Document + context tracking ────────────────────────────────────────────────


def _detect_doc_format(lines: list[str]) -> str:
    """
    Return 'azdo', 'gha', or 'unknown' based on document signals.

    AzDO: has '- template:' lines (with or without @alias) or 'azure-pipelines' keywords
    GHA:  has 'uses:' with '.github/workflows/' or 'runs-on:' with 'on:' block
    """
    text = "\n".join(lines[:80])  # only scan first 80 lines for speed
    if re.search(r"^on:\s*$|workflow_call|runs-on:", text, re.MULTILINE):
        return "gha"
    if re.search(r"-\s+template\s*:", text, re.MULTILINE):
        return "azdo"
    # Fallback: any yaml with azure pipeline stage/step/job keys → azdo
    if re.search(r"^stages:|^jobs:|^steps:|^trigger:|^pool:", text, re.MULTILINE):
        return "azdo"
    return "unknown"


def _detect_azdo_context(lines: list[str], line_idx: int, char_idx: int) -> dict:
    """
    Return context dict for AzDO completion at (line_idx, char_idx).

    Detects:
      - 'template_path': cursor is on a '- template:' line value
      - 'param_name': cursor is inside 'parameters:' block below a known template
      - 'unknown'
    """
    current = lines[line_idx][:char_idx] if line_idx < len(lines) else ""
    indent = len(current) - len(current.lstrip())

    # Are we ON a '- template:' line?
    if re.search(r"-\s+template:\s*", current):
        # Extract partial path typed so far
        m = re.search(r"-\s+template:\s*(\S*)$", current)
        prefix = m.group(1) if m else ""
        return {"type": "template_path", "format": "azdo", "prefix": prefix}

    # Are we in a 'parameters:' block? Scan backwards for the enclosing template line
    lookback = lines[max(0, line_idx - 40) : line_idx + 1]
    lookback = list(lookback)
    lookback[-1] = lookback[-1][:char_idx]

    # Find the most recent '- template: PATH@ALIAS' above cursor
    template_key = None
    in_params_block = False
    for i in range(len(lookback) - 1, -1, -1):
        ln = lookback[i]
        # Detect '- template: tasks/k8s/deploy.yaml@pipeline-templates'
        m = re.search(r"-\s+template:\s+(\S+@\S+)", ln)
        if m:
            template_key = m.group(1)
            break
        # Detect entering a 'parameters:' block
        if re.match(r"\s*parameters\s*:", ln):
            in_params_block = True

    if template_key and in_params_block:
        # Check if cursor is after 'paramname: ' (value context)
        value_m = re.match(r"\s*-\s+(\w+)\s*:\s*(.*)$", current)
        if value_m:
            return {
                "type": "param_value",
                "format": "azdo",
                "template_key": template_key,
                "param": value_m.group(1),
            }
        # Otherwise: parameter name completion
        return {"type": "param_name", "format": "azdo", "template_key": template_key}

    return {"type": "unknown", "format": "azdo"}


def _detect_gha_context(lines: list[str], line_idx: int, char_idx: int) -> dict:
    """
    Return context dict for GHA completion at (line_idx, char_idx).

    Detects:
      - 'workflow_ref': cursor is on a 'uses:' line value
      - 'input_name': cursor is inside 'with:' block below a known 'uses:' line
      - 'unknown'
    """
    current = lines[line_idx][:char_idx] if line_idx < len(lines) else ""

    # Are we ON a 'uses:' line?
    if re.match(r"\s*uses\s*:", current):
        m = re.search(r"uses:\s*(\S*)$", current)
        prefix = m.group(1) if m else ""
        return {"type": "workflow_ref", "format": "gha", "prefix": prefix}

    # Scan back for the enclosing 'uses:' line inside a step
    lookback = lines[max(0, line_idx - 20) : line_idx + 1]
    lookback = list(lookback)
    lookback[-1] = lookback[-1][:char_idx]

    template_key = None
    in_with_block = False
    for i in range(len(lookback) - 1, -1, -1):
        ln = lookback[i]
        # 'uses: org/repo/.github/workflows/file.yml@ref'
        m = re.search(r"uses:\s+(\S+/\.github/workflows/\S+)", ln)
        if m:
            template_key = m.group(1)
            break
        if re.match(r"\s+with\s*:", ln):
            in_with_block = True

    if template_key and in_with_block:
        return {"type": "input_name", "format": "gha", "template_key": template_key}

    return {"type": "unknown", "format": "gha"}


# ── Completion injection ───────────────────────────────────────────────────────


def _inject_completions(msg: dict[str, Any], context: dict) -> bytes:
    """Inject template-aware items at the top of a completion response."""
    result = msg.get("result")
    if result is None:
        return json.dumps(msg).encode()

    items: list | None = None
    if isinstance(result, list):
        items = result
    elif isinstance(result, dict) and "items" in result:
        items = result["items"]

    if items is None:
        return json.dumps(msg).encode()

    ctx_type = context.get("type", "unknown")
    fmt = context.get("format", "unknown")
    lru_items: list[dict[str, Any]] = []

    if ctx_type == "template_path" and fmt == "azdo":
        lru_items = PipelineTemplateCatalog.azdo_template_completion_items()
    elif ctx_type == "param_name" and fmt == "azdo":
        key = context.get("template_key", "")
        lru_items = PipelineTemplateCatalog.azdo_param_completion_items(key)
    elif ctx_type == "param_value" and fmt == "azdo":
        key = context.get("template_key", "")
        param = context.get("param", "")
        lru_items = PipelineTemplateCatalog.azdo_param_value_items(key, param)
    elif ctx_type == "workflow_ref" and fmt == "gha":
        lru_items = PipelineTemplateCatalog.gha_workflow_completion_items()
    elif ctx_type == "input_name" and fmt == "gha":
        key = context.get("template_key", "")
        lru_items = PipelineTemplateCatalog.gha_input_completion_items(key)

    if not lru_items:
        return json.dumps(msg).encode()

    # Downgrade existing items' sortText so LRU items appear first
    for item in items:
        st = item.get("sortText", item.get("label", ""))
        item["sortText"] = "9_" + st

    if isinstance(result, list):
        msg["result"] = lru_items + items
    else:
        result["items"] = lru_items + items
        msg["result"] = result

    return json.dumps(msg).encode()


# ── Proxy session ─────────────────────────────────────────────────────────────


class _YamlSession:
    """Per-WebSocket state: document lines and pending completion requests."""

    def __init__(self) -> None:
        self.docs: dict[str, list[str]] = {}   # uri → lines
        self.pending: dict = {}                  # request_id → context dict

    def update_doc(self, uri: str, text: str) -> None:
        self.docs[uri] = text.splitlines()

    def record_request(self, msg: dict) -> None:
        req_id = msg.get("id")
        if req_id is None:
            return
        params = msg.get("params", {})
        uri = params.get("textDocument", {}).get("uri", "")
        position = params.get("position", {})
        lines = self.docs.get(uri, [])
        doc_format = _detect_doc_format(lines)
        line_idx = position.get("line", 0)
        char_idx = position.get("character", 0)

        if doc_format == "azdo":
            ctx = _detect_azdo_context(lines, line_idx, char_idx)
        elif doc_format == "gha":
            ctx = _detect_gha_context(lines, line_idx, char_idx)
        else:
            ctx = {"type": "unknown", "format": "unknown"}

        self.pending[req_id] = ctx

    def pop_context(self, msg_id) -> dict:
        return self.pending.pop(msg_id, {"type": "unknown", "format": "unknown"})


# ── Main WS handler ───────────────────────────────────────────────────────────


async def yaml_ws_handler(request: web.Request, yaml_lsp_port: int = 0) -> web.WebSocketResponse:
    """
    WebSocket handler for the /yaml endpoint.

    Spawns yaml-language-server --stdio per editor connection (one process per
    session). Bridges WS ↔ process stdin/stdout, intercepting completion messages
    to inject pipeline template completions.

    Note: yaml_lsp_port is unused — kept for API compatibility.
    yaml-language-server uses --stdio so no TCP port is needed.
    """
    import shutil

    ws = web.WebSocketResponse()
    await ws.prepare(request)

    yaml_ls = shutil.which("yaml-language-server")
    if not yaml_ls:
        logger.error("yaml-language-server not found in PATH")
        await ws.close(code=1011, message=b"yaml-language-server not installed", timeout=2.0)
        return ws

    try:
        proc = await asyncio.create_subprocess_exec(
            yaml_ls, "--stdio",
            stdin=asyncio.subprocess.PIPE,
            stdout=asyncio.subprocess.PIPE,
            stderr=asyncio.subprocess.DEVNULL,
        )
    except Exception as exc:
        logger.error("Failed to start yaml-language-server: %s", exc)
        await ws.close(code=1011, message=b"YAML LSP failed to start", timeout=2.0)
        return ws

    logger.info("yaml-language-server started (--stdio) PID=%d", proc.pid)

    session = _YamlSession()
    ws_buf = _LspFrameBuffer()
    proc_buf = _LspFrameBuffer()

    async def client_to_server() -> None:
        """WS → stdin: track document content and completion requests."""
        try:
            async for msg in ws:
                if msg.type not in (WSMsgType.BINARY, WSMsgType.TEXT):
                    continue
                raw = msg.data if msg.type == WSMsgType.BINARY else msg.data.encode()
                frames = ws_buf.feed(raw)
                for frame in frames:
                    try:
                        parsed = json.loads(frame)
                        method = parsed.get("method", "")
                        if method in ("textDocument/didOpen", "textDocument/didChange"):
                            params = parsed.get("params", {})
                            uri = params.get("textDocument", {}).get("uri", "")
                            text = params.get("textDocument", {}).get("text") or ""
                            if not text:
                                changes = params.get("contentChanges", [])
                                if changes:
                                    text = changes[-1].get("text", "")
                            if uri and text:
                                session.update_doc(uri, text)
                        elif method == "textDocument/completion":
                            session.record_request(parsed)
                    except Exception:
                        pass
                    proc.stdin.write(_lsp_frame(frame))
                await proc.stdin.drain()
        except Exception:
            pass
        finally:
            try:
                proc.stdin.close()
            except Exception:
                pass
            proc.kill()

    async def server_to_client() -> None:
        """stdout → WS: inject completions into completion responses."""
        try:
            while True:
                data = await proc.stdout.read(_CHUNK)
                if not data:
                    break
                frames = proc_buf.feed(data)
                for frame in frames:
                    try:
                        parsed = json.loads(frame)
                        msg_id = parsed.get("id")
                        if msg_id is not None and "result" in parsed:
                            ctx = session.pop_context(msg_id)
                            modified = _inject_completions(parsed, ctx)
                            await ws.send_bytes(_lsp_frame(modified))
                            continue
                    except Exception:
                        pass
                    await ws.send_bytes(_lsp_frame(frame))
        except Exception:
            pass
        finally:
            await ws.close()

    await asyncio.gather(client_to_server(), server_to_client(), return_exceptions=True)
    try:
        proc.kill()
    except Exception:
        pass
    logger.info("yaml-language-server session ended PID=%d", proc.pid)
    return ws