#!/usr/bin/env bash
# Auto-generate a changeset from conventional commit messages when none exists.
# Run in CI before `npx changeset version`.
#
# Bump mapping (intentionally conservative — automated releases are always patch):
#   fix:, feat:, perf:    → patch
#   feat!: / BREAKING CHANGE → major
#   chore:, ci:, docs:, refactor:, style:, test:, build: → no release
#
# Minor bumps must be declared explicitly via `npx changeset` before pushing.
# If no releasable commits are found, exits cleanly — changeset version
# then has nothing to consume and publish is a no-op.
set -euo pipefail

CHANGESET_DIR=".changeset"
PACKAGES=("__PACKAGE_NAME__")

# Skip if a manually-authored changeset already exists
EXISTING=$(find "$CHANGESET_DIR" -name "*.md" ! -name "README.md" | wc -l)
if [ "$EXISTING" -gt 0 ]; then
  echo "→ Changeset already present — skipping auto-generation"
  exit 0
fi

# Commits since last tag, or all commits if repo has no tags yet
LAST_TAG=$(git describe --tags --abbrev=0 2>/dev/null || echo "")
if [ -n "$LAST_TAG" ]; then
  RANGE="${LAST_TAG}..HEAD"
else
  RANGE="HEAD"
fi

SUBJECTS=$(git log "$RANGE" --pretty=format:"%s" 2>/dev/null || true)
FULL_LOG=$(git log "$RANGE" --pretty=format:"%s%n%b" 2>/dev/null || true)

if [ -z "$SUBJECTS" ]; then
  echo "→ No commits in range — skipping auto-generation"
  exit 0
fi

BUMP=""
SUMMARY_LINES=()

while IFS= read -r line; do
  [ -z "$line" ] && continue
  if echo "$line" | grep -qE "^[a-z]+(\([^)]+\))?!:" || echo "$line" | grep -qE "^BREAKING CHANGE"; then
    BUMP="major"
  fi
  if echo "$line" | grep -qE "^(fix|feat|perf)(\([^)]+\))?:" && [ -z "$BUMP" ]; then
    BUMP="patch"
  fi
done <<< "$FULL_LOG"

while IFS= read -r line; do
  [ -z "$line" ] && continue
  if echo "$line" | grep -qE "^(fix|feat|perf)(\([^)]+\))?:"; then
    SUMMARY_LINES+=("- $line")
  fi
done <<< "$SUBJECTS"

if [ -z "$BUMP" ]; then
  echo "→ No releasable commits (fix:/feat:/perf:) since ${LAST_TAG:-beginning} — skipping"
  exit 0
fi

FRONTMATTER=""
for pkg in "${PACKAGES[@]}"; do
  FRONTMATTER="${FRONTMATTER}\"${pkg}\": ${BUMP}"$'\n'
done

DESCRIPTION=$(printf '%s\n' "${SUMMARY_LINES[@]}")
FILENAME="${CHANGESET_DIR}/auto-$(date +%s)-$$.md"

cat > "$FILENAME" <<EOF
---
${FRONTMATTER}---

${DESCRIPTION}
EOF

echo "→ Generated ${FILENAME} (bump: ${BUMP})"
cat "$FILENAME"