#!/usr/bin/env bash
set -euo pipefail

: "${FILE:?FILE is required}"
: "${LATEST_RELEASE_URL:?LATEST_RELEASE_URL is required}"
: "${DOWNLOAD_URL_TEMPLATE:?DOWNLOAD_URL_TEMPLATE is required}"
: "${RELEASE_API_REPO:?RELEASE_API_REPO is required}"

if command -v python >/dev/null 2>&1; then
  PYTHON_BIN=python
elif command -v python3 >/dev/null 2>&1; then
  PYTHON_BIN=python3
else
  echo "python is required but was not found"
  exit 1
fi

version_strip_prefix="${LATEST_VERSION_STRIP_PREFIX:-v}"
release_tag_template="${RELEASE_TAG_TEMPLATE:-{version}}"
release_tag_template="${release_tag_template//$'\r'/}"

current_version=$($PYTHON_BIN - <<'PY'
import re
import os
p=os.environ["FILE"]
s=open(p).read()
m=re.search(r'version\s*=\s*"([^"]+)";', s)
print(m.group(1) if m else "")
PY
)

latest_version=$(curl -fsSLI -o /dev/null -w '%{url_effective}' "$LATEST_RELEASE_URL" \
  | sed -E 's#.*/##')

if [ -n "$version_strip_prefix" ]; then
  latest_version="${latest_version#${version_strip_prefix}}"
fi

echo "current=$current_version"
echo "latest=$latest_version"

if [ -z "$latest_version" ] || [ "$latest_version" = "$current_version" ]; then
  echo "updated=false" >> "$GITHUB_OUTPUT"
  exit 0
fi

download_url="${DOWNLOAD_URL_TEMPLATE//\{version\}/$latest_version}"
new_hash=$(nix store prefetch-file --json "$download_url" | "$PYTHON_BIN" -c 'import json,sys; print(json.load(sys.stdin)["hash"])')

export LATEST_VERSION="$latest_version"
export NEW_HASH="$new_hash"

"$PYTHON_BIN" - <<'PY'
import os
import re
p=os.environ["FILE"]
s=open(p).read()
s=re.sub(r'version\s*=\s*"[^"]+"', f'version = "{os.environ["LATEST_VERSION"]}"', s, count=1)
s=re.sub(r'hash\s*=\s*"[^"]+"', f'hash = "{os.environ["NEW_HASH"]}"', s, count=1)
open(p,"w").write(s)
PY

echo "updated=true" >> "$GITHUB_OUTPUT"
echo "version=$latest_version" >> "$GITHUB_OUTPUT"
echo "previous_version=$current_version" >> "$GITHUB_OUTPUT"

release_tag="${release_tag_template//\{version\}/$latest_version}"
release_tag="${release_tag#\{}"
release_tag="${release_tag%\}}"
release_tag="${release_tag#\'}"
release_tag="${release_tag%\'}"

release_url="${LATEST_RELEASE_URL%/latest}/tag/${release_tag}"
release_html=$(curl -fsSL "$release_url" || true)

release_notes=""
if [ -n "$release_html" ]; then
  release_notes=$(printf '%s' "$release_html" | "$PYTHON_BIN" -c '
import re
import sys
from html.parser import HTMLParser

html = sys.stdin.read()

m = re.search(r"<div[^>]*data-test-selector=\"body-content\"[^>]*class=\"[^\"]*markdown-body[^\"]*\"[^>]*>(.*?)</div>", html, re.S)
if not m:
  print("")
  raise SystemExit(0)

fragment = m.group(1)

class MdExtractor(HTMLParser):
  def __init__(self):
    super().__init__()
    self.out = []
    self.list_depth = 0
    self.in_pre = False
    self.in_code_inline = False
    self.link_stack = []

  def _append(self, text):
    self.out.append(text)

  def _ensure_newline(self):
    if not self.out:
      return
    if not self.out[-1].endswith("\n"):
      self.out.append("\n")

  def _ensure_blank_line(self):
    if not self.out:
      return
    joined = "".join(self.out)
    if joined.endswith("\n\n"):
      return
    if joined.endswith("\n"):
      self.out.append("\n")
    else:
      self.out.append("\n\n")

  def handle_starttag(self, tag, attrs):
    attrs_d = dict(attrs)

    if tag in ("h1", "h2", "h3", "h4", "h5", "h6"):
      self._ensure_blank_line()
      level = int(tag[1])
      self._append("#" * level + " ")
      return

    if tag in ("p", "div"):
      self._ensure_blank_line()
      return

    if tag in ("ul", "ol"):
      self._ensure_blank_line()
      self.list_depth += 1
      return

    if tag == "li":
      self._ensure_newline()
      indent = "  " * max(self.list_depth - 1, 0)
      self._append(f"{indent}- ")
      return

    if tag == "br":
      self._append("\n")
      return

    if tag == "pre":
      self._ensure_blank_line()
      self._append("```\n")
      self.in_pre = True
      return

    if tag == "code":
      if not self.in_pre:
        self._append("`")
        self.in_code_inline = True
      return

    if tag == "a":
      href = attrs_d.get("href", "")
      self.link_stack.append(href)
      self._append("[")
      return

    if tag in ("strong", "b"):
      self._append("**")
      return

    if tag in ("em", "i"):
      self._append("*")
      return

  def handle_endtag(self, tag):
    if tag in ("h1", "h2", "h3", "h4", "h5", "h6", "p", "div"):
      self._ensure_blank_line()
      return

    if tag in ("ul", "ol"):
      self.list_depth = max(self.list_depth - 1, 0)
      self._ensure_blank_line()
      return

    if tag == "li":
      self._ensure_newline()
      return

    if tag == "pre":
      self._ensure_newline()
      self._append("```\n\n")
      self.in_pre = False
      return

    if tag == "code":
      if not self.in_pre and self.in_code_inline:
        self._append("`")
        self.in_code_inline = False
      return

    if tag == "a":
      href = self.link_stack.pop() if self.link_stack else ""
      if href:
        self._append("]("
          + href
          + ")")
      else:
        self._append("]")
      return

    if tag in ("strong", "b"):
      self._append("**")
      return

    if tag in ("em", "i"):
      self._append("*")
      return

  def handle_data(self, data):
    if data:
      self._append(data)

parser = MdExtractor()
parser.feed(fragment)
text = "".join(parser.out)
text = re.sub(r"\n{3,}", "\n\n", text)
text = re.sub(r"[ \t]+\n", "\n", text)
print(text.strip())
' || true)
else
  echo "warning: failed to fetch release page ${release_url}"
fi

if [ -z "$release_notes" ]; then
  release_notes="_No changelog found on upstream release page. Check ${release_url}._"
fi

delimiter="CHANGELOG_$(date +%s%N)"
{
  echo "changelog<<${delimiter}"
  printf '%s\n' "$release_notes"
  echo "${delimiter}"
} >> "$GITHUB_OUTPUT"