#!/usr/bin/env bash
set -eu pipefail

MERMAID_DIR="static/js"
MERMAID_FILE="mermaid.min.js"
MERMAID_PATH="${MERMAID_DIR}/${MERMAID_FILE}"
UGLIFY_ITERATIONS=5
TEMP_DIR=$(mktemp -d)

cleanup() {
    rm -rf "$TEMP_DIR"
}

trap cleanup EXIT

exit_with_message() {
    echo "$1" >&2
    exit 1
}

check_dependency() {
    if ! command -v "$1" &> /dev/null; then
        exit_with_message "$1 is required but not installed."
    fi
}

get_latest_version_jsdelivr() {
    curl -s https://data.jsdelivr.com/v1/package/npm/mermaid | jq -r '.tags.latest'
}

get_latest_version_github() {
    curl -s https://api.github.com/repos/mermaid-js/mermaid/releases/latest |
    jq -r '.tag_name' |
    sed -E 's/^v?mermaid@?//'  # Remove 'v', 'mermaid@', or both if present.
}

compare_md5() {
    local new_file="$1"
    local current_file="$2"
    local new_md5=$(md5sum "$new_file" | awk '{ print $1 }')

    if [ -f "$current_file" ]; then
        local current_md5=$(md5sum "$current_file" | awk '{ print $1 }')
        if [ "$new_md5" = "$current_md5" ]; then
            echo "same"
        else
            echo "different"
        fi
    else
        echo "new"
    fi
}

uglify_file() {
    local output_file="$1"
    local iterations="$2"

    for i in $(seq 1 "$iterations"); do
        echo "Running UglifyJS iteration $i"
        uglifyjs --compress --mangle -- "$output_file" > "${output_file}.tmp"
        mv "${output_file}.tmp" "$output_file"
    done
}

generate_commit_message() {
    local template="$1"
    local version="$2"
    echo "${template//\{VERSION\}/${version}}"
}

upgrade_mermaid() {
    if [ ! -d "$MERMAID_DIR" ]; then
        exit_with_message "Directory ${MERMAID_DIR} does not exist. Are you running this script from the root of the repository?"
    fi

    local commit_msg_template=$(cat << EOM
⬆️ chore(deps): upgrade mermaid to v{VERSION}

Changelog: https://github.com/mermaid-js/mermaid/releases/tag/mermaid%40{VERSION}

Source: https://cdn.jsdelivr.net/npm/mermaid@{VERSION}/dist/mermaid.min.js
EOM
)

    local latest_version=$(get_latest_version_jsdelivr || get_latest_version_github)

    if [ -z "$latest_version" ]; then
        exit_with_message "Unable to determine the latest Mermaid.js version."
    fi

    echo "Latest Mermaid.js version: ${latest_version}"

    local download_url="https://cdn.jsdelivr.net/npm/mermaid@${latest_version}/dist/mermaid.min.js"
    curl -L "${download_url}" -o "${TEMP_DIR}/${MERMAID_FILE}"

    uglify_file "${TEMP_DIR}/${MERMAID_FILE}" "$UGLIFY_ITERATIONS"

    local comparison_result=$(compare_md5 "${TEMP_DIR}/${MERMAID_FILE}" "${MERMAID_PATH}")

    case "$comparison_result" in
        "same")
            echo "New version is the same as current version. No update needed."
            return 0
            ;;
        "different")
            echo "New version differs from current version. Proceeding with update."
            mv "${TEMP_DIR}/${MERMAID_FILE}" "${MERMAID_PATH}"
            ;;
        "new")
            echo "Creating new file: ${MERMAID_PATH}"
            mv "${TEMP_DIR}/${MERMAID_FILE}" "${MERMAID_PATH}"
            ;;
    esac

    echo "Mermaid.js updated and minified successfully!"
    echo "Preparing to commit changes…"
    git add "${MERMAID_PATH}"
    local commit_msg=$(generate_commit_message "$commit_msg_template" "$latest_version")
    git commit -m "${commit_msg}"

    echo "Most recent commit:"
    git log -1

    echo "To push the changes:"
    echo "git push"
}

main() {
    check_dependency "jq"
    check_dependency "uglifyjs"
    check_dependency "curl"
    check_dependency "git"
    check_dependency "sed"
    check_dependency "awk"
    check_dependency "md5sum"

    local default_branch=$(git remote show origin | sed -n '/HEAD branch/s/.*: //p')
    local current_branch=$(git rev-parse --abbrev-ref HEAD)
    if [ "$current_branch" != "$default_branch" ]; then
        exit_with_message "Not on $default_branch branch. Switch to $default_branch before running this script."
    fi

    if ! git diff --cached --quiet; then
        exit_with_message "There are staged changes. Unstage them before running this script."
    fi

    echo "Updating local repository…"
    git fetch origin
    local git_status=$(git status -uno)
    if echo "$git_status" | grep -q "Your branch is behind"; then
        exit_with_message "Your local branch is behind the remote. Pull the latest changes before running this script."
    elif echo "$git_status" | grep -q "Your branch is ahead"; then
        echo "Your local branch is ahead of the remote. Checking if local changes can be pushed…"
        if ! git push --dry-run &> /dev/null; then
            exit_with_message "Unable to push local changes. Resolve any conflicts before running this script."
        fi
    elif ! echo "$git_status" | grep -q "Your branch is up to date"; then
        exit_with_message "Unable to determine if branch is up to date. Check your git status manually."
    fi
    echo "Local repository is ready."

    upgrade_mermaid
}

main "$@"