"""Parser for markdown files into Entity objects.

Uses markdown-it with plugins to parse structured data from markdown content.
"""

from dataclasses import dataclass, field
from pathlib import Path
from datetime import datetime
from typing import Any, Optional
import dateparser

from markdown_it import MarkdownIt
import frontmatter

from basic_memory.markdown.plugins import observation_plugin, relation_plugin
from basic_memory.markdown.schemas import (
    EntityMarkdown,
    EntityFrontmatter,
    Observation,
    Relation,
)

md = MarkdownIt().use(observation_plugin).use(relation_plugin)


@dataclass
class EntityContent:
    content: str
    observations: list[Observation] = field(default_factory=list)
    relations: list[Relation] = field(default_factory=list)


def parse(content: str) -> EntityContent:
    """Parse markdown content into EntityMarkdown."""

    # Parse content for observations and relations using markdown-it
    observations = []
    relations = []

    if content:
        for token in md.parse(content):
            # check for observations and relations
            if token.meta:
                if "observation" in token.meta:
                    obs = token.meta["observation"]
                    observation = Observation.model_validate(obs)
                    observations.append(observation)
                if "relations" in token.meta:
                    rels = token.meta["relations"]
                    relations.extend([Relation.model_validate(r) for r in rels])

    return EntityContent(
        content=content,
        observations=observations,
        relations=relations,
    )


def parse_tags(tags: Any) -> list[str]:
    """Parse tags into list of strings."""
    if isinstance(tags, (list, tuple)):
        return [str(t).strip() for t in tags if str(t).strip()]
    return [t.strip() for t in tags.split(",") if t.strip()]


class EntityParser:
    """Parser for markdown files into Entity objects."""

    def __init__(self, base_path: Path):
        """Initialize parser with base path for relative permalink generation."""
        self.base_path = base_path.resolve()

    def parse_date(self, value: Any) -> Optional[datetime]:
        """Parse date strings using dateparser for maximum flexibility.

        Supports human friendly formats like:
        - 2024-01-15
        - Jan 15, 2024
        - 2024-01-15 10:00 AM
        - yesterday
        - 2 days ago
        """
        if isinstance(value, datetime):
            return value
        if isinstance(value, str):
            parsed = dateparser.parse(value)
            if parsed:
                return parsed
        return None

    async def parse_file(self, path: Path | str) -> EntityMarkdown:
        """Parse markdown file into EntityMarkdown."""

        absolute_path = self.base_path / path
        # Parse frontmatter and content using python-frontmatter
        post = frontmatter.load(str(absolute_path))

        # Extract file stat info
        file_stats = absolute_path.stat()

        metadata = post.metadata
        metadata["title"] = post.metadata.get("title", absolute_path.name)
        metadata["type"] = post.metadata.get("type", "note")
        metadata["tags"] = parse_tags(post.metadata.get("tags", []))

        # frontmatter
        entity_frontmatter = EntityFrontmatter(
            metadata=post.metadata,
        )

        entity_content = parse(post.content)

        return EntityMarkdown(
            frontmatter=entity_frontmatter,
            content=post.content,
            observations=entity_content.observations,
            relations=entity_content.relations,
            created=datetime.fromtimestamp(file_stats.st_ctime),
            modified=datetime.fromtimestamp(file_stats.st_mtime),
        )