#!/bin/bash
# pr-merge.sh - Merge pull requests on Gitea or GitHub
# Usage: pr-merge.sh -n PR_NUMBER [-m squash] [-d] [--skip-queue-guard] [--dry-run]

set -e

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
# shellcheck disable=SC1091
source "$SCRIPT_DIR/detect-platform.sh"

# Default values
PR_NUMBER=""
MERGE_METHOD="squash"
DELETE_BRANCH=false
SKIP_QUEUE_GUARD=false
DRY_RUN=false

usage() {
    cat <<EOF
Usage: $(basename "$0") [OPTIONS]

Merge a pull request on the current repository (Gitea or GitHub).

Options:
    -n, --number NUMBER     PR number to merge (required)
    -m, --method METHOD     Merge method: squash only (default: squash)
    -d, --delete-branch     Delete the head branch after merge
        --skip-queue-guard  Skip CI queue guard wait before merge
        --dry-run           Validate metadata/auth/preflight without merging
    -h, --help              Show this help message

Examples:
    $(basename "$0") -n 42                    # Merge PR #42
    $(basename "$0") -n 42 -m squash          # Squash merge
    $(basename "$0") -n 42 -d                 # Squash merge and delete branch
    $(basename "$0") -n 42 --skip-queue-guard # Skip queue guard wait
EOF
    exit 1
}

# Parse arguments
while [[ $# -gt 0 ]]; do
    case $1 in
        -n|--number)
            PR_NUMBER="$2"
            shift 2
            ;;
        -m|--method)
            MERGE_METHOD="$2"
            shift 2
            ;;
        -d|--delete-branch)
            DELETE_BRANCH=true
            shift
            ;;
        --skip-queue-guard)
            SKIP_QUEUE_GUARD=true
            shift
            ;;
        --dry-run)
            DRY_RUN=true
            shift
            ;;
        -h|--help)
            usage
            ;;
        *)
            echo "Unknown option: $1" >&2
            usage
            ;;
    esac
done

if [[ -z "$PR_NUMBER" ]]; then
    echo "Error: PR number is required (-n)" >&2
    usage
fi

if [[ "$MERGE_METHOD" != "squash" ]]; then
    echo "Error: Mosaic policy enforces squash merge only. Received '$MERGE_METHOD'." >&2
    exit 1
fi

METADATA_JSON="$("$SCRIPT_DIR/pr-metadata.sh" -n "$PR_NUMBER")"
BASE_BRANCH="$(printf '%s' "$METADATA_JSON" | python3 -c 'import json, sys; print((json.load(sys.stdin).get("baseRefName") or "").strip())')"
if [[ "$BASE_BRANCH" != "main" ]]; then
    echo "Error: Mosaic policy allows merges only for PRs targeting 'main' (found '$BASE_BRANCH')." >&2
    exit 1
fi

if [[ "$SKIP_QUEUE_GUARD" != true ]]; then
    "$SCRIPT_DIR/ci-queue-wait.sh" \
        --purpose merge \
        -B "$BASE_BRANCH" \
        -t "${MOSAIC_CI_QUEUE_TIMEOUT_SEC:-900}" \
        -i "${MOSAIC_CI_QUEUE_POLL_SEC:-15}"
fi

PLATFORM=$(detect_platform)
OWNER=$(get_repo_owner)
REPO=$(get_repo_name)

case "$PLATFORM" in
    github)
        if [[ "$DRY_RUN" == true ]]; then
            echo "Dry run: GitHub merge preflight OK for ${OWNER}/${REPO}#${PR_NUMBER} targeting ${BASE_BRANCH}"
            exit 0
        fi
        CMD=(gh pr merge "$PR_NUMBER" --squash)
        [[ "$DELETE_BRANCH" == true ]] && CMD+=(--delete-branch)
        "${CMD[@]}"
        ;;
    gitea)
        HOST=$(get_remote_host) || {
            echo "Error: Cannot determine host from remote URL" >&2
            exit 1
        }
        TOKEN=$(get_gitea_token "$HOST") || {
            echo "Error: Could not resolve Gitea API token for ${HOST}" >&2
            exit 1
        }

        if [[ "$DRY_RUN" == true ]]; then
            echo "Dry run: Gitea merge preflight OK for ${OWNER}/${REPO}#${PR_NUMBER} targeting ${BASE_BRANCH} via ${HOST} API"
            exit 0
        fi

        RESPONSE_FILE=$(mktemp)
        trap 'rm -f "$RESPONSE_FILE"' EXIT
        HTTP_CODE=$(curl -sS \
            -X POST \
            -H "Authorization: token $TOKEN" \
            -H "Content-Type: application/json" \
            -d '{"Do":"squash"}' \
            -o "$RESPONSE_FILE" \
            -w '%{http_code}' \
            "https://${HOST}/api/v1/repos/${OWNER}/${REPO}/pulls/${PR_NUMBER}/merge")
        RESPONSE_BODY=$(cat "$RESPONSE_FILE")
        rm -f "$RESPONSE_FILE"
        trap - EXIT

        if [[ ! "$HTTP_CODE" =~ ^2 ]]; then
            echo "Error: Gitea PR merge failed for ${OWNER}/${REPO}#${PR_NUMBER} (HTTP ${HTTP_CODE})" >&2
            if [[ -n "$RESPONSE_BODY" ]]; then
                printf '%s\n' "$RESPONSE_BODY" >&2
            fi
            exit 1
        fi

        # Delete branch after merge if requested
        if [[ "$DELETE_BRANCH" == true ]]; then
            echo "Note: Branch deletion after merge may need to be done separately with the Gitea API" >&2
        fi
        ;;
    *)
        echo "Error: Could not detect git platform" >&2
        exit 1
        ;;
esac

echo "PR #$PR_NUMBER merged successfully"