#!/usr/bin/env bash
# Vendored from heavy-duty/ceremony 0.6.3:
#   lib/changelog.sh (changelog_section + changelog_section_problem)
#   bin/changelog-section

set -euo pipefail

changelog_section() {
  awk -v ver="$2" '
    /^## / { if (found) exit; found = ($2 == ver); next }
    found && !body && /^[[:space:]]*$/ { next }
    found { body = 1; print }
  ' "$1"
}

changelog_section_problem() {
  local file="$1" ver="$2" notes problem

  if ! awk -v ver="$ver" '/^## / && $2 == ver { found = 1; exit } END { exit !found }' "$file"; then
    printf "no section for '%s'\n" "$ver"
    return 1
  fi

  [ "$ver" = "Unreleased" ] && return 0

  notes="$(changelog_section "$file" "$ver")"
  if ! printf '%s\n' "$notes" | awk '/^[[:space:]]*[-*][[:space:]]/ { found = 1; exit } END { exit !found }'; then
    printf "section '%s' has no entries — a heading is not an entry\n" "$ver"
    return 1
  fi

  problem="$(
    printf '%s\n' "$notes" | awk '
      /^### / {
        if (heading != "" && !entry) {
          reported = 1
          print heading
          exit
        }
        heading = $0
        entry = 0
        next
      }
      heading != "" && /^[[:space:]]*[-*][[:space:]]/ { entry = 1 }
      END {
        if (!reported && heading != "" && !entry) print heading
      }
    '
  )"
  if [ -n "$problem" ]; then
    printf "section '%s' has an empty heading: '%s'\n" "$ver" "$problem"
    return 1
  fi
}

ver="${1:-}"
changelog="${2:-CHANGELOG.md}"
if [ -z "$ver" ]; then
  echo "usage: changelog-section.sh <version> [<changelog>]" >&2
  exit 2
fi
[ -f "$changelog" ] || {
  echo "changelog-section: no such file: $changelog" >&2
  exit 1
}

if ! diagnosis="$(changelog_section_problem "$changelog" "$ver")"; then
  echo "changelog-section: $changelog has no publishable section for '$ver'" >&2
  printf 'changelog-section: %s\n' "$diagnosis" >&2
  exit 1
fi
notes="$(changelog_section "$changelog" "$ver")"
printf '%s\n' "$notes"