"""ActivityDefinition markdown file parser (T44).

Scans activity-definitions/*.md in the local repo and any directories
listed in ACTIVITY_DEFINITION_DIRS (colon-separated). Returns parsed
ActivityDefinitionDef objects; raises ParseError on malformed input.

Never silently ignores a broken definition file.
"""

from __future__ import annotations

import os
import re
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any

import yaml


class ParseError(Exception):
    """Raised when a definition file cannot be parsed."""

    def __init__(self, file: Path, line: int | None, message: str) -> None:
        self.file = file
        self.line = line
        self.message = message
        loc = f"{file}:{line}" if line else str(file)
        super().__init__(f"{loc}: {message}")


@dataclass
class ActivityDefinitionDef:
    """Parsed in-memory representation of an activity-definitions/*.md file."""

    id: str
    name: str
    enabled: bool
    trigger_config: dict[str, Any]
    context_sources: list[dict[str, Any]]
    rules: list[dict[str, Any]]
    instructions: list[dict[str, Any]]
    governance: str
    owner: str
    status: str
    source_file: Path


_FRONTMATTER_RE = re.compile(r"^---\s*\n(.*?)\n---\s*\n", re.DOTALL)
_FENCED_BLOCK_RE = re.compile(r"^```(\w+)\s*\n(.*?)\n```", re.DOTALL | re.MULTILINE)


def _scan_dirs() -> list[Path]:
    dirs: list[Path] = []
    default_dir = Path("activity-definitions")
    if default_dir.is_dir():
        dirs.append(default_dir)
    extra = os.environ.get("ACTIVITY_DEFINITION_DIRS", "")
    for part in extra.split(":"):
        part = part.strip()
        if not part:
            continue
        p = Path(part) / "activity-definitions"
        if p.is_dir():
            dirs.append(p)
    return dirs


def _parse_trigger(trigger_dict: dict, file: Path) -> dict[str, Any]:
    """Normalise the trigger section into a trigger_config dict."""
    trigger_type = trigger_dict.get("type")
    if trigger_type == "cron":
        return {
            "trigger_type": "cron",
            "cron_expression": trigger_dict.get("cron_expression", ""),
            "timezone": trigger_dict.get("timezone", "UTC"),
            "jitter_seconds": trigger_dict.get("jitter_seconds", 0),
            "misfire_policy": trigger_dict.get("misfire_policy", "skip"),
        }
    elif trigger_type == "event":
        return {
            "trigger_type": "event",
            "event_type": trigger_dict.get("event_type", ""),
            "filters": trigger_dict.get("filters", {}),
        }
    elif trigger_type == "scheduled":
        at = trigger_dict.get("at")
        if at is None:
            raise ParseError(file, None, "trigger.at is required for type=scheduled")
        at_str = at.isoformat() if hasattr(at, "isoformat") else str(at)
        return {
            "trigger_type": "scheduled",
            "at": at_str,
            "timezone": trigger_dict.get("timezone", "UTC"),
        }
    else:
        raise ParseError(file, None, f"unknown trigger type {trigger_type!r}")


def parse_file(path: Path) -> ActivityDefinitionDef:
    """Parse one ActivityDefinition markdown file.

    Raises ParseError on malformed or missing required fields.
    """
    try:
        text = path.read_text(encoding="utf-8")
    except OSError as exc:
        raise ParseError(path, None, f"cannot read file: {exc}") from exc

    fm_match = _FRONTMATTER_RE.match(text)
    if not fm_match:
        raise ParseError(path, 1, "missing or malformed YAML frontmatter")

    try:
        fm = yaml.safe_load(fm_match.group(1))
    except yaml.YAMLError as exc:
        raise ParseError(path, None, f"YAML parse error in frontmatter: {exc}") from exc

    if not isinstance(fm, dict):
        raise ParseError(path, 1, "frontmatter must be a YAML mapping")

    for req in ("id", "name", "trigger"):
        if req not in fm:
            raise ParseError(path, None, f"missing required frontmatter field: {req!r}")

    trigger_section = fm["trigger"]
    if not isinstance(trigger_section, dict):
        raise ParseError(path, None, "trigger must be a YAML mapping")

    trigger_config = _parse_trigger(trigger_section, path)

    raw_sources = fm.get("context_sources", []) or []
    context_sources: list[dict[str, Any]] = []
    for cs in raw_sources:
        if not isinstance(cs, dict):
            raise ParseError(path, None, "each context_source must be a mapping")
        context_sources.append(cs)

    # Parse fenced rule/instruction blocks from the body
    body = text[fm_match.end():]
    rules: list[dict[str, Any]] = []
    instructions: list[dict[str, Any]] = []

    for block_match in _FENCED_BLOCK_RE.finditer(body):
        lang = block_match.group(1).strip()
        block_body = block_match.group(2)
        try:
            block_data = yaml.safe_load(block_body)
        except yaml.YAMLError as exc:
            raise ParseError(path, None, f"YAML parse error in {lang!r} block: {exc}") from exc

        if lang == "rule":
            if not isinstance(block_data, dict):
                raise ParseError(path, None, "rule block must be a YAML mapping")
            if "id" not in block_data:
                raise ParseError(path, None, "rule block missing required field 'id'")
            if "action" not in block_data:
                raise ParseError(path, None, f"rule {block_data['id']!r} missing 'action'")
            rules.append(block_data)
        elif lang == "instruction":
            if not isinstance(block_data, dict):
                raise ParseError(path, None, "instruction block must be a YAML mapping")
            if "id" not in block_data:
                raise ParseError(path, None, "instruction block missing required field 'id'")
            instructions.append(block_data)

    return ActivityDefinitionDef(
        id=str(fm["id"]),
        name=str(fm["name"]),
        enabled=bool(fm.get("enabled", True)),
        trigger_config=trigger_config,
        context_sources=context_sources,
        rules=rules,
        instructions=instructions,
        governance=str(fm.get("governance", "publisher-declared")),
        owner=str(fm.get("owner", "")),
        status=str(fm.get("status", "active")),
        source_file=path,
    )


def scan_and_parse() -> list[ActivityDefinitionDef]:
    """Scan all definition directories and parse all .md files.

    Raises ParseError on any broken file — never silently skips.
    """
    dirs = _scan_dirs()
    defs: list[ActivityDefinitionDef] = []
    for d in dirs:
        for path in sorted(d.glob("*.md")):
            defs.append(parse_file(path))
    return defs