#!/usr/bin/env python3
"""Folge dem Markdown-/Hugo-internen Link unter dem Cursor.

Aufruf:  hugo-link.py <buffile> <cursor_line> <cursor_column>

Gibt auf stdout genau ein Kakoune-Kommando aus:
  * edit -existing '<pfad>'   -> Zieldatei oeffnen
  * nop %sh{ xdg-open ... }   -> externe URL im Browser
  * echo -markup '{Error}..'  -> nichts gefunden / Fehler
"""
import os
import re
import shlex
import sys


def kak_str(s):
    """String fuer Kakoune in einfachen Anfuehrungszeichen quoten."""
    return "'" + s.replace("'", "''") + "'"


def emit_and_exit(cmd):
    print(cmd)
    sys.exit(0)


def fail(msg):
    emit_and_exit("echo -markup " + kak_str("{Error}" + msg))


CONFIG_NAMES = (
    "hugo.toml", "hugo.yaml", "hugo.yml", "hugo.json",
    "config.toml", "config.yaml", "config.yml", "config.json",
)

# [text](ziel "optionaler Titel")  bzw.  [text](<ziel>)
LINK_RE = re.compile(r'\[[^\]]*\]\(\s*<?([^)>\s]+)>?(?:\s+"[^"]*")?\s*\)')
# <https://...>  Autolink
AUTOLINK_RE = re.compile(r'<([a-zA-Z][\w+.-]*:[^>\s]+)>')


def find_site_root(start):
    d = start
    while True:
        if any(os.path.exists(os.path.join(d, n)) for n in CONFIG_NAMES):
            return d
        if os.path.isdir(os.path.join(d, "content")):
            return d
        parent = os.path.dirname(d)
        if parent == d:
            return None
        d = parent


def target_under_cursor(line, idx):
    for regex in (LINK_RE, AUTOLINK_RE):
        for m in regex.finditer(line):
            if m.start() <= idx < m.end():
                return m.group(1)
    return None


def open_external(target):
    emit_and_exit("nop %%sh{ setsid xdg-open %s >/dev/null 2>&1 & }"
                  % shlex.quote(target))


def main():
    if len(sys.argv) != 4:
        fail("interner Aufruffehler")
    buffile, line_s, col_s = sys.argv[1], sys.argv[2], sys.argv[3]
    line_no, col = int(line_s), int(col_s)

    try:
        with open(buffile, encoding="utf-8") as fh:
            lines = fh.read().split("\n")
    except OSError as exc:
        fail("kann Buffer nicht lesen: %s" % exc)

    if not 1 <= line_no <= len(lines):
        fail("Cursor ausserhalb des Buffers")
    line = lines[line_no - 1]

    target = target_under_cursor(line, col - 1)
    if target is None:
        fail("kein Link unter dem Cursor")

    # Fragment (#...) und Query (?...) abtrennen
    target = re.split(r'[#?]', target, maxsplit=1)[0]
    if not target:
        fail("Link zeigt nur auf einen Anker")

    if (re.match(r'^[a-zA-Z][a-zA-Z0-9+.-]*://', target)
            or target.startswith("//")
            or target.startswith("mailto:")):
        open_external(target)

    buf_dir = os.path.dirname(os.path.abspath(buffile))

    if target.startswith("/"):
        root = find_site_root(buf_dir)
        if root is None:
            fail("kein Hugo-Root (hugo.toml / config.*) oberhalb gefunden")
        content_dir = os.path.join(root, "content")
        if not os.path.isdir(content_dir):
            content_dir = root
        base = os.path.normpath(
            os.path.join(content_dir, target.lstrip("/")))
    else:
        base = os.path.normpath(os.path.join(buf_dir, target))

    if base.endswith(".md"):
        candidates = [base]
    else:
        candidates = [
            base + ".md",
            os.path.join(base, "_index.md"),
            os.path.join(base, "index.md"),
            base,  # z.B. direkt verlinktes Bild / statische Datei
        ]

    for cand in candidates:
        if os.path.isfile(cand):
            emit_and_exit("edit -existing " + kak_str(cand))

    fail("Ziel nicht gefunden: " + " | ".join(candidates))


if __name__ == "__main__":
    main()