import dataclasses
import datetime
import json
import re
from decimal import Decimal
from logging import getLogger
from pathlib import Path
from typing import Any

import frontmatter
import marko
import marko.md_renderer

logger = getLogger(__name__)

StatisticKey = str


@dataclasses.dataclass(frozen=True)
class Event:
    start_time: datetime.time | None
    end_time: datetime.time | None
    verb: str | None
    subject: str | None
    comment: str

    def __post_init__(self):
        if self.subject:
            assert ':' not in self.subject
            assert '/' not in self.subject


@dataclasses.dataclass(frozen=True)
class FileContents:
    frontmatter: dict[str, Any]
    blocks_pre_events: list
    events: frozenset[Event]
    blocks_post_events: list


MARKDOWN_PARSER = marko.Markdown()
MARKDOWN_RENDERER = marko.md_renderer.MarkdownRenderer()

FILE_FORMAT = """
{blocks_pre_events}
## Events
{block_events}
{blocks_post_events}
"""


class ObsidianVault:
    def __init__(self, vault_path: Path, read_only: bool = 'silent'):
        self.vault_path = vault_path

        assert (self.vault_path / '.obsidian').exists(), 'Not an Obsidian Vault'

        with open(self.vault_path / '.obsidian' / 'daily-notes.json') as f:
            daily_notes_config = json.load(f)
        self.daily_folder = daily_notes_config['folder']
        self.path_format = daily_notes_config['format']
        self.template_file_path = daily_notes_config['template']
        self.read_only = read_only

    def get_statistic(
        self,
        date: datetime.date,
        statistic_key: StatisticKey,
    ) -> Any | None:
        if contents := self._get_date_contents(date):
            return contents.frontmatter.get(statistic_key)
        return None

    def add_statistic(
        self,
        date: datetime.date,
        statistic_key: StatisticKey,
        amount: Any,
    ) -> bool:
        # Adjust arguments
        if isinstance(amount, Decimal):
            amount = float(amount)

        # Check for silent
        if self.read_only == 'silent':
            logger.info(
                'Read-only ObsidianVault ignoring add_statistic(%s, "%s", %s)',
                date,
                statistic_key,
                amount,
            )
            return False

        # Load contents
        self._create_date_if_not_present(date)
        contents = self._get_date_contents(date)

        # Update contents
        if contents.frontmatter.get(statistic_key) == amount:
            return False

        contents.frontmatter[statistic_key] = amount
        if amount is None:
            del contents.frontmatter[statistic_key]

        # Save contents
        self._save_contents(date, contents)
        return True

    def add_events(self, date: datetime.date, events: list[Event]) -> bool:
        if self.read_only == 'silent':
            logger.info(
                'Read-only ObsidianVault ignoring add_event(%s, "%s", ?)',
                date,
                events,
            )
        if not self.read_only:
            self._create_date_if_not_present(date)

        contents = self._get_date_contents(date)
        if contents is None:
            return False

        # Exit without writing if there were no changes.
        updated_events: frozenset[Event] = contents.events | set(events)
        if contents.events == updated_events:
            return False

        contents = dataclasses.replace(contents, events = updated_events)
        if not self.read_only:
            self._save_contents(date, contents)
        return True

    def get_events(self, date: datetime.date) -> frozenset[Event]:
        contents = self._get_date_contents(date)
        if contents is None:
            return frozenset()
        return contents.events

    def _get_date_contents(self, date: datetime.date) -> FileContents | None:
        try:
            with open(self._date_file_path(date)) as f:
                file_frontmatter = frontmatter.load(f)
        except FileNotFoundError:
            return None

        ast = MARKDOWN_PARSER.parse(str(file_frontmatter))
        (pre_events, list_block_items, post_events) = find_events_list_block(ast)
        events = frozenset(parse_event_string(list_item) for list_item in list_block_items)
        return FileContents(file_frontmatter.metadata, pre_events, events, post_events)

    def _save_contents(self, date: datetime.date, contents: FileContents) -> None:
        logger.info('Formatting file "%s"', date)
        blocks_pre_events = ''.join(
            MARKDOWN_RENDERER.render(b) for b in contents.blocks_pre_events
        )
        blocks_post_events = ''.join(
            MARKDOWN_RENDERER.render(b) for b in contents.blocks_post_events
        )

        events = sorted(contents.events, key=lambda x: x.start_time or x.end_time)
        block_events = '\n'.join(
            '- ' + format_event_string(e) for e in events
        )
        text = FILE_FORMAT.format(
            blocks_pre_events=blocks_pre_events,
            blocks_post_events=blocks_post_events,
            block_events=block_events,
        ).strip()

        logger.info('Saving file "%s"', date)
        with open(self._date_file_path(date), 'wb') as f:
            frontmatter.dump(frontmatter.Post(text, **contents.frontmatter), f)

    def _create_date_if_not_present(self, date: datetime.date):
        date_file = self._date_file_path(date)
        if date_file.exists():
            return
        logger.info('File "%s" doesn\'t exist, creating...', date)
        with open(self._daily_template_path()) as f:
            template_text = f.read()
        date_file.parent.mkdir(exist_ok=True, parents=True)
        with open(date_file, 'w') as f:
            f.write(template_text)

    def _date_file_path(self, date: datetime.date):
        path = (
            self.path_format.replace('YYYY', str(date.year))
            .replace('MM', f'{date.month:02d}')
            .replace('DD', f'{date.day:02d}')
        )
        return (self.vault_path / self.daily_folder / path).with_suffix('.md')

    def _daily_template_path(self):
        return (self.vault_path / self.template_file_path).with_suffix('.md')


def find_events_list_block(ast) -> tuple[list, list[str], list]:
    blocks = ast.children
    for block_i, block in enumerate(blocks):
        if (
            isinstance(block, marko.block.Heading)
            and block.children[0].children.lower() == 'events'
        ):
            events_block = ast.children[block_i + 1]
            if isinstance(events_block, marko.block.List):
                offset = 2
                event_texts = [
                    MARKDOWN_RENDERER.render_children(li).strip()
                    for li in events_block.children
                ]
            else:
                offset = 1
                event_texts = []

            return (blocks[:block_i], event_texts, blocks[block_i + offset :])
    return (blocks, [], [])


def format_event_string(event: Event) -> str:
    assert event is not None
    if (
        event.start_time is None
        and event.end_time is None
        and event.subject is None
        and event.verb is None
    ):
        return event.comment

    buf = []
    buf.append(f'{event.start_time:%H:%M}')
    if event.end_time and event.end_time != event.start_time:
        buf.append(f'-{event.end_time:%H:%M}')
    buf.append(' | ')
    buf.append(event.verb)
    buf.append(' [[')
    buf.append(event.subject)
    buf.append(']].')
    buf.append((' ' + event.comment).strip())

    return ''.join(buf)


RE_TIME = r'(\d\d:\d\d(?::\d\d(?:\.\d+?))?)'
RE_VERB = r'(\w+(?:ed|te))'
RE_LINK_MD = r'\[([^\]:/]*)\]\(?:[^)]*\)'
RE_LINK_WIKI = r'\[\[([^\]:/]*)\]\]'

RE_TIME_FORMAT = RE_TIME + r'(?:\s*\-\s*' + RE_TIME + r')?'


def parse_event_string(event_str: str) -> Event:
    if m := re.match(
        r'^\s*' + RE_TIME_FORMAT + r'[ :\|-]*'+RE_VERB+r'\s+'+RE_LINK_MD+r'\.?\s*(.*)$',
        event_str,
    ):
        start = datetime.time.fromisoformat(m.group(1))
        end = datetime.time.fromisoformat(m.group(2)) if m.group(2) else start
        return Event(start, end, m.group(3), m.group(4), m.group(5))
    if m := re.match(
            r'^\s*' + RE_TIME_FORMAT + r'[ :\|-]*'+RE_VERB+r'\s+'+RE_LINK_WIKI+r'\.?\s*(.*)$',
        event_str,
    ):
        start = datetime.time.fromisoformat(m.group(1))
        end = datetime.time.fromisoformat(m.group(2)) if m.group(2) else start
        return Event(start, end, m.group(3), m.group(4), m.group(5))
    logger.info('Could not parse format: %s', event_str)
    return Event(None, None, None, None, event_str)