#!/usr/bin/env bash
#
# .git/hooks/post-merge
#
# After merging to main, asks Claude Code to review and update documentation.
# Changes are left unstaged for your review.
#
# Setup:
#   cp post-merge .git/hooks/post-merge
#   chmod +x .git/hooks/post-merge
#
# Requires Claude Code CLI to be installed and authenticated.

set -euo pipefail

# Only run on main branch
CURRENT_BRANCH=$(git symbolic-ref --short HEAD)
if [ "$CURRENT_BRANCH" != "main" ]; then
  exit 0
fi

echo "📝 Checking documentation after merge to main..."

# Capture what changed in the merge so Claude has context
DIFF=$(git diff ORIG_HEAD..HEAD --stat)

# Build the prompt
PROMPT="A feature branch was just merged to main. Here is a summary of what changed:

$DIFF

Please review the following documentation and update anything that is out of date
or missing given the changes above:

- README.md
- docs/decisions.md (add an entry if a significant architectural decision was made)
- Any relevant files in docs/explainers/
- Any relevant product documentation in docs/

Do not modify AGENTS.md or any files in docs/plans/ or docs/specs/.

After making changes, print a brief summary of what you updated and why.
If nothing needed updating, say so."

# Run Claude Code in non-interactive mode with read/write permissions only
claude -p "$PROMPT" \
  --allowedTools "Read" "Write" "Glob" "Grep" \
  --max-turns 10

# Show which files were changed (if any)
DOC_CHANGES=$(git diff --name-only -- README.md 'docs/**' 2>/dev/null || true)

if [ -n "$DOC_CHANGES" ]; then
  echo ""
  echo "✅ Documentation updated. Review changes before committing:"
  echo "$DOC_CHANGES" | sed 's/^/   /'
  echo ""
  echo "   Run 'git diff' to review, then 'git add' and 'git commit' when ready."
else
  echo "✅ No documentation changes were necessary."
fi