#!/usr/bin/env python3
"""Build the site from flat Obsidian Markdown notes."""

from __future__ import annotations

import datetime as dt
import html
import re
import shutil
import sys
from dataclasses import dataclass
from pathlib import Path
from urllib.parse import quote
import markdown as md


ROOT = Path(__file__).resolve().parent.parent
POSTS = ROOT / "posts"
PAGES = ROOT / "pages"
BUILD = ROOT / "bld"


@dataclass
class Note:
    path: Path
    slug: str
    title: str
    display: str
    order: int
    link: str | None
    date: dt.datetime | None
    tags: list[str]
    body: str


def clean_tag(tag: str) -> str:
    return tag.strip().lstrip("#").replace("/", "-").replace(" ", "-").lower()


def parse_front_matter(text: str) -> tuple[dict[str, object], str]:
    if not text.startswith("---\n"):
        return {}, text
    end = re.search(r"^---\s*$", text[4:], re.M)
    if not end:
        return {}, text
    raw = text[4 : 4 + end.start()]
    data: dict[str, object] = {}
    for line in raw.splitlines():
        if not line or line.lstrip().startswith("#") or ":" not in line:
            continue
        key, value = line.split(":", 1)
        value = value.strip().strip("\"'")
        if value.startswith("[") and value.endswith("]"):
            data[key.strip().lower()] = [v.strip().strip("\"'") for v in value[1:-1].split(",") if v.strip()]
        elif value:
            data[key.strip().lower()] = value
    return data, text[4 + end.end() :].lstrip("\n")


def parse_date(value: object) -> dt.datetime | None:
    if not value:
        return None
    text = str(value).strip().replace("Z", "+00:00")
    for pattern in ("%Y-%m-%d %H:%M", "%Y-%m-%d", "%Y/%m/%d %H:%M", "%Y/%m/%d"):
        try:
            return dt.datetime.strptime(text, pattern)
        except ValueError:
            pass
    try:
        return dt.datetime.fromisoformat(text)
    except ValueError:
        raise ValueError(f"Invalid date: {value!r}. Use YYYY-MM-DD or YYYY-MM-DD HH:MM.")


def parse_note(path: Path, post: bool = False) -> Note:
    meta, body = parse_front_matter(path.read_text(encoding="utf-8"))
    heading = re.search(r"^#\s+(.+?)\s*$", body, re.M)
    title = str(meta.get("title") or (heading.group(1) if heading else path.stem.replace("-", " ")))
    display = str(meta.get("display") or title)
    order = int(meta.get("order") or 0)
    link = str(meta.get("link")) if meta.get("link") else None
    if heading and not meta.get("title"):
        body = body[: heading.start()] + body[heading.end() :].lstrip("\n")
    raw_tags = meta.get("tags", [])
    if isinstance(raw_tags, str):
        raw_tags = [piece.strip() for piece in raw_tags.split(",")]
    tags = [clean_tag(str(tag)) for tag in raw_tags]
    if post:
        tags.extend(clean_tag(match) for match in re.findall(r"(?<![\w/])#([\w][\w/-]*)", body))
    tags = list(dict.fromkeys(tag for tag in tags if tag))
    return Note(path, path.stem, title, display, order, link, parse_date(meta.get("date")), tags, body)


def inline(text: str) -> str:
    text = html.escape(text, quote=False)
    text = re.sub(r"!\[([^]]*)\]\(([^ )]+)(?:\s+[^)]*)?\)", r'<img src="\2" alt="\1">', text)
    text = re.sub(r"\[([^]]+)\]\(([^ )]+)(?:\s+[^)]*)?\)", r'<a href="\2">\1</a>', text)
    text = re.sub(r"\[\[([^]|]+)(?:\|([^]]+))?\]\]", lambda m: f'<a href="{quote(m.group(1).replace(" ", "-") + ".html")}">{m.group(2) or m.group(1)}</a>', text)
    text = re.sub(r"`([^`]+)`", r"<code>\1</code>", text)
    text = re.sub(r"\*\*([^*]+)\*\*|__([^_]+)__", lambda m: f"<strong>{m.group(1) or m.group(2)}</strong>", text)
    text = re.sub(r"(?<!\*)\*([^*]+)\*(?!\*)|(?<!_)_([^_]+)_(?!_)", lambda m: f"<em>{m.group(1) or m.group(2)}</em>", text)
    return text


def markdown(text: str) -> str:
    return md.markdown(text)
    lines, output, paragraph, in_code, list_type = text.splitlines(), [], [], False, None

    def flush_paragraph() -> None:
        nonlocal paragraph
        if paragraph:
            output.append(f"<p>{inline(' '.join(part.strip() for part in paragraph))}</p>")
            paragraph = []

    def close_list() -> None:
        nonlocal list_type
        if list_type:
            output.append(f"</{list_type}>")
            list_type = None

    for line in lines:
        if line.startswith("```"):
            flush_paragraph(); close_list()
            output.append("</code></pre>" if in_code else "<pre><code>")
            in_code = not in_code
        elif in_code:
            output.append(html.escape(line))
        elif not line.strip():
            flush_paragraph(); close_list()
        elif match := re.match(r"^(#{1,6})\s+(.+)$", line):
            flush_paragraph(); close_list()
            level = len(match.group(1)); output.append(f"<h{level}>{inline(match.group(2))}</h{level}>")
        elif line.startswith("> "):
            flush_paragraph(); close_list(); output.append(f"<blockquote><p>{inline(line[2:])}</p></blockquote>")
        elif line.strip() in ("---", "***", "___"):
            flush_paragraph(); close_list(); output.append("<hr>")
        elif match := re.match(r"^\s*([-+*]|\d+\.)\s+(.+)$", line):
            flush_paragraph()
            kind = "ol" if match.group(1)[0].isdigit() else "ul"
            if list_type != kind:
                close_list(); output.append(f"<{kind}>"); list_type = kind
            output.append(f"<li>{inline(match.group(2))}</li>")
        else:
            paragraph.append(line)
    flush_paragraph(); close_list()
    return "\n".join(output)


def tag_links(tags: list[str], prefix: str = "") -> str:
    return " ".join(f'<a class="tag" href="{prefix}tags/{quote(tag)}.html">#{html.escape(tag)}</a>' for tag in tags)


def page(title: str, content: str, nav: str = "") -> str:
    return f"""<!doctype html>
<html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1">
<title>{html.escape(title)}</title><link rel="stylesheet" href="{nav}style.css"></head>
<body><main>{content}</main></body></html>\n"""


def post_html(note: Note) -> str:
    date = note.date.strftime("%Y/%m/%d %H:%M") if note.date else "Undated"
    return page(note.title, f'<a class="back" href="index.html">← index</a><article><header><h1>{html.escape(note.display)}</h1><p class="metadata">{date} &nbsp; {tag_links(note.tags)}</p></header>{markdown(note.body)}</article>')


def list_html(posts: list[Note], heading: str, static_pages: list[Note], tag: str | None = None) -> str:
    rows = []
    for note in posts:
        if tag is None or tag in note.tags:
            date = note.date.strftime("%Y/%m/%d %H:%M") if note.date else "Undated"
            prefix = "../" if tag else ""
            tags = tag_links(note.tags, prefix)
            rows.append(f'<li><time>{date}</time><a class="post-link" href="{prefix}{quote(note.slug)}.html">{html.escape(note.title)}</a><span class="tags">{tags}</span></li>')
    extras = ""
    if static_pages:
        page_prefix = "../" if tag else ""
        links = " · ".join(f'<a href="{note.link or f"{page_prefix}{quote(note.slug)}.html"}">{html.escape(note.title)}</a>' for note in static_pages)
        extras = f'<nav class="pages">{links}</nav>'
    back = '<a class="back" href="../index.html">← index</a>' if tag else ""
    empty = "<p class=\"empty\">No posts yet.</p>" if not rows else f"<ol class=\"post-list\">{''.join(rows)}</ol>"
    return page(heading, f'{back}<header class="list-header"><h1>{html.escape(heading)}</h1>{extras}</header>{empty}', "../" if tag else "")


def copy_assets() -> None:
    for source in POSTS.iterdir():
        if not source.is_file() or source.suffix.lower() == ".md":
            continue
        shutil.copy2(source, BUILD / source.name)
    for source in PAGES.iterdir():
            if not source.is_file() or source.suffix.lower() == ".md":
                continue
            shutil.copy2(source, BUILD / source.name)


def main() -> None:
    for directory in (POSTS, PAGES):
        directory.mkdir(exist_ok=True)
    if BUILD.exists():
        shutil.rmtree(BUILD)
    (BUILD / "tags").mkdir(parents=True)
    posts = [parse_note(path, True) for path in POSTS.glob("*.md")]
    for note in posts:
        if note.date is None:
            raise ValueError(f"{note.path.relative_to(ROOT)} needs a date in its front matter")
    posts.sort(key=lambda note: note.date or dt.datetime.min, reverse=True)
    static_pages = [parse_note(path) for path in PAGES.glob("*.md")]
    static_pages.sort(key=lambda note: note.order or 0)
    for note in posts:
        (BUILD / f"{note.slug}.html").write_text(post_html(note), encoding="utf-8")
    for note in static_pages:
        body = f'<a class="back" href="index.html">← index</a><article><h1>{html.escape(note.display)}</h1>{markdown(note.body)}</article>'
        (BUILD / f"{note.slug}.html").write_text(page(note.title, body), encoding="utf-8")
    (BUILD / "index.html").write_text(list_html(posts, "Alejandro's blog", static_pages), encoding="utf-8")
    tags = sorted({tag for note in posts for tag in note.tags})
    for tag in tags:
        (BUILD / "tags" / f"{tag}.html").write_text(list_html(posts, f"#{tag}", static_pages, tag), encoding="utf-8")
    shutil.copy2(ROOT / "style.css", BUILD / "style.css")
    copy_assets()
    print(f"Built {len(posts)} post(s), {len(tags)} tag page(s), and {len(static_pages)} page(s) in {BUILD.relative_to(ROOT)}/")


if __name__ == "__main__":
    try:
        main()
    except (OSError, ValueError) as error:
        sys.exit(f"compile: {error}")