#!/usr/bin/env bash

set -Eeuo pipefail

script_name=$(basename "$0")
version="0.1.0"

usage() {
    cat <<EOF
Usage:
  $script_name get [git clone flags...] <repo>

Config:
  gj.root   Existing directory where repositories are stored.

Examples:
  $script_name get org/repo
  $script_name get gitlab.com/org/repo
  $script_name get https://github.com/org/repo
  $script_name get --depth 1 git@gitlab.com:org/repo.git
EOF
}

die() {
    printf '%s\n' "$*" >&2
    exit 1
}

require_git() {
    command -v git >/dev/null 2>&1 || die "git is required on PATH"
}

expand_shorthand() {
    local input=$1

    # Full URLs and scp-like syntax pass through untouched.
    if [[ "$input" =~ ^[a-zA-Z][a-zA-Z0-9+.-]*:// || "$input" == *@*:* ]]; then
        printf '%s\n' "$input"
    # org/repo defaults to GitHub.
    elif [[ "$input" =~ ^[a-zA-Z0-9_.-]+/[a-zA-Z0-9_.-]+$ ]]; then
        printf 'https://github.com/%s\n' "$input"
    # host/org/repo works for any remote (e.g. gitlab.com/org/repo).
    elif [[ "$input" =~ ^[a-zA-Z0-9.-]+\.[a-zA-Z]+(/[a-zA-Z0-9_.-]+){2,}$ ]]; then
        printf 'https://%s\n' "$input"
    else
        return 1
    fi
}

parse_repo() {
    local input=$1
    local path no_scheme

    if [[ "$input" =~ ^[a-zA-Z][a-zA-Z0-9+.-]*:// ]]; then
        no_scheme="${input#*://}"
        path="${no_scheme#*/}"
    elif [[ "$input" == *@*:* ]]; then
        path="${input#*:}"
    else
        path="${input#*/}"
    fi

    path="${path#/}"
    path="${path%.git}"

    if [[ -z "$path" || "$path" != */* ]]; then
        return 1
    fi

    printf '%s\n' "$path"
}

run_get() {
    local repo url dest rel
    local flags=()

    if [[ $# -lt 1 ]]; then
        usage
        exit 2
    fi

    root=$(git config --global --get gj.root || true)
    if [[ -z "$root" ]]; then
        die "gj.root is not set in git config"
    fi

    root="${root/#\~/$HOME}"
    if [[ ! -d "$root" ]]; then
        die "gj.root does not exist: $root"
    fi

    if [[ $# -eq 1 ]]; then
        repo="$1"
    else
        repo="${*: -1}"
        flags=("${@:1:$#-1}")
    fi

    if ! url=$(expand_shorthand "$repo"); then
        die "Could not parse repo: $repo"
    fi
    repo="$url"

    if ! rel=$(parse_repo "$repo"); then
        die "Could not parse repo: $repo"
    fi

    dest="$root/$rel"

    if [[ -e "$dest" ]]; then
        if [[ -d "$dest/.git" ]]; then
            git -C "$dest" remote update --prune
            printf '%s\n' "$dest"
            return 0
        fi
        die "Destination exists and is not a git repo: $dest"
    fi

    mkdir -p "$(dirname "$dest")"
    git clone ${flags[@]+"${flags[@]}"} "$repo" "$dest"
    printf '%s\n' "$dest"
}

main() {
    if [[ $# -lt 1 ]]; then
        usage
        exit 2
    fi

    case "$1" in
    -h | --help)
        usage
        exit 0
        ;;
    --version)
        printf '%s\n' "$version"
        exit 0
        ;;
    get)
        shift
        require_git
        run_get "$@"
        ;;
    *)
        die "Unknown command: $1"
        ;;
    esac
}

main "$@"