#!/bin/bash

# Script to resolve searchindex.js conflicts by accepting master branch version
# This script is designed to handle merge conflicts that occur when PRs become
# desynchronized due to the auto-generated searchindex.js file.
# 
# The searchindex.js file is automatically generated by the build process and
# frequently causes conflicts when multiple PRs are waiting to be merged.
# This script automatically resolves those conflicts by accepting the master
# branch version of the file.
#
# Usage: resolve_searchindex_conflicts.sh <pr_number> <head_branch> <base_branch>

set -euo pipefail

# Validate arguments
if [ $# -ne 3 ]; then
    echo "Usage: $0 <pr_number> <head_branch> <base_branch>"
    exit 1
fi

PR_NUMBER="$1"
HEAD_BRANCH="$2"
BASE_BRANCH="$3"

# Validate required environment variables
if [ -z "${GITHUB_REPOSITORY:-}" ]; then
    echo "Error: GITHUB_REPOSITORY environment variable is required"
    exit 1
fi

if [ -z "${GH_TOKEN:-}" ]; then
    echo "Error: GH_TOKEN environment variable is required"
    exit 1
fi

echo "Resolving conflicts for PR #$PR_NUMBER (branch: $HEAD_BRANCH -> $BASE_BRANCH)"

# Get current directory for safety
ORIGINAL_DIR=$(pwd)

# Create a temporary directory for the operation
TEMP_DIR=$(mktemp -d)
echo "Working in temporary directory: $TEMP_DIR"

cleanup() {
    echo "Cleaning up..."
    cd "$ORIGINAL_DIR"
    rm -rf "$TEMP_DIR"
}
trap cleanup EXIT

# Clone the repository to the temp directory
echo "Cloning repository..."
cd "$TEMP_DIR"
gh repo clone "$GITHUB_REPOSITORY" . -- --branch "$HEAD_BRANCH"

# Configure git
git config user.email "action@github.com"
git config user.name "GitHub Action"

# Fetch all branches
git fetch origin

# Make sure we're on the correct branch
git checkout "$HEAD_BRANCH"

# Try to merge the base branch
echo "Attempting to merge $BASE_BRANCH into $HEAD_BRANCH..."
if git merge "origin/$BASE_BRANCH" --no-edit; then
    echo "No conflicts found, merge successful"
    
    # Push the updated branch
    echo "Pushing merged branch..."
    git push origin "$HEAD_BRANCH"
    exit 0
fi

# Check what files have conflicts
echo "Checking for conflicts..."
conflicted_files=$(git diff --name-only --diff-filter=U)
echo "Conflicted files: $conflicted_files"

# Check if searchindex.js is the only conflict or if conflicts are only in acceptable files
acceptable_conflicts=true
searchindex_conflict=false

for file in $conflicted_files; do
    case "$file" in
        "searchindex.js")
            searchindex_conflict=true
            echo "Found searchindex.js conflict (acceptable)"
            ;;
        *)
            echo "Found unacceptable conflict in: $file"
            acceptable_conflicts=false
            ;;
    esac
done

if [ "$acceptable_conflicts" = false ]; then
    echo "Cannot auto-resolve: conflicts found in files other than searchindex.js"
    git merge --abort
    exit 1
fi

if [ "$searchindex_conflict" = false ]; then
    echo "No searchindex.js conflicts found, but merge failed for unknown reason"
    git merge --abort
    exit 1
fi

echo "Resolving searchindex.js conflict by accepting $BASE_BRANCH version..."

# Accept the base branch version of searchindex.js (--theirs refers to the branch being merged in)
git checkout --theirs searchindex.js
git add searchindex.js

# Check if there are any other staged changes from the merge
staged_files=$(git diff --cached --name-only || true)
echo "Staged files after resolution: $staged_files"

# Complete the merge
if git commit --no-edit; then
    echo "Successfully resolved merge conflicts"
    
    # Push the updated branch
    echo "Pushing resolved branch..."
    if git push origin "$HEAD_BRANCH"; then
        echo "Successfully pushed resolved branch"
        exit 0
    else
        echo "Failed to push resolved branch"
        exit 1
    fi
else
    echo "Failed to commit merge resolution"
    exit 1
fi