#!/bin/bash
# client-credentials - Obtain an OAuth2 access token via the client_credentials grant
#
# Usage:
#   client-credentials [options]
#   client-credentials -h
#
# Options:
#   -e, --endpoint       Endpoint type: am or slas (default: am)
#   -c, --client-id      Client ID (overrides J_CLIENT_ID)
#   -s, --client-secret  Client secret (overrides J_CLIENT_SECRET)
#   -S, --scopes         Scopes (optional; overrides J_SCOPES)
#   -C, --shortcode      Shortcode (required for slas; overrides J_SHORTCODE)
#   -o, --org-id         Organization ID (required for slas; overrides J_ORG_ID)
#   -h, --help           Show help message

_client_credentials() (
    local SCRIPT_NAME; SCRIPT_NAME="$(basename "${BASH_SOURCE[0]}")"
    case "${BASH_SOURCE[0]}" in /dev/*|/proc/*) SCRIPT_NAME="" ;; esac
    case "$SCRIPT_NAME" in ""|bash|sh|zsh|dash) SCRIPT_NAME="client-credentials" ;; esac

    _error() { echo "[ERR][$SCRIPT_NAME] $*" >&2; }

    _show_help() {
        local s; [ -t 1 ] && s=$'\033[4m'
        local r; [ -t 1 ] && r=$'\033[24m'
        cat <<EOF
NAME
  $SCRIPT_NAME - obtain an OAuth2 access token via the client_credentials grant
SYNOPSIS
  $SCRIPT_NAME [${s}options${r}]
  $SCRIPT_NAME -h
DESCRIPTION
  Obtains an OAuth2 access token via the client_credentials grant.
  Supports Salesforce Account Manager (AM) and Shopper Login API
  Service (SLAS) endpoints used by Salesforce B2C Commerce Cloud.

  AM endpoint:
    https://account.demandware.com/dwsso/oauth2/access_token
  SLAS endpoint:
    https://{shortcode}.api.commercecloud.salesforce.com/shopper/auth/v1/organizations/{org_id}/oauth2/token

  Prints the access token to stdout. Capture it with command substitution:
    TOKEN=\$($SCRIPT_NAME -c "\$J_CLIENT_ID" -s "\$J_CLIENT_SECRET")
OPTIONS
  -e, --endpoint ${s}type${r}       Endpoint type: am or slas (default: am)
  -c, --client-id ${s}id${r}        Client ID (overrides J_CLIENT_ID)
  -s, --client-secret ${s}secret${r}
                            Client secret (overrides J_CLIENT_SECRET)
  -S, --scopes ${s}scopes${r}       Space-separated scopes (overrides J_SCOPES)
  -C, --shortcode ${s}shortcode${r} Shortcode (SLAS; overrides J_SHORTCODE)
  -o, --org-id ${s}org_id${r}       Organization ID (SLAS; overrides J_ORG_ID)
  -h, --help                Show this help message
ENVIRONMENT
  Input (overridden by the matching flag):
    J_ENDPOINT               am or slas
    J_CLIENT_ID              Client ID
    J_CLIENT_SECRET          Client secret
    J_SCOPES                 Scopes
    J_SHORTCODE              Shortcode (SLAS)
    J_ORG_ID                 Organization ID (SLAS)
EXIT STATUS
  0  Success
  1  Runtime failure (request failed)
  2  Usage error (unknown flag, invalid endpoint, missing required parameter)
DEPENDENCIES
  curl, jq, base64
EOF
    }

    _expand_short_opts() {
        # $1 = string of short-opt letters that take a value (e.g. "nXHd"); "" for flag-only scripts
        # $2..$N = "$@"
        # Populates _EXPANDED; caller does: set -- "${_EXPANDED[@]}"; unset _EXPANDED
        local value_opts="$1"; shift
        _EXPANDED=()
        local passthru=""
        local arg
        local rest
        local c
        for arg in "$@"; do
            if [ -n "$passthru" ]; then _EXPANDED+=("$arg"); continue; fi
            case "$arg" in
                --)          passthru=1; _EXPANDED+=("$arg") ;;
                --*|-|"")    _EXPANDED+=("$arg") ;;
                -[a-zA-Z]?*)
                    rest="${arg#-}"
                    while [ -n "$rest" ]; do
                        c="${rest%"${rest#?}"}"; rest="${rest#?}"
                        _EXPANDED+=("-$c")
                        case "$value_opts" in *"$c"*)
                            [ -n "$rest" ] && _EXPANDED+=("$rest")
                            rest="" ;;
                        esac
                    done ;;
                *)           _EXPANDED+=("$arg") ;;
            esac
        done
    }

    # Initialize from environment or defaults
    local endpoint="${J_ENDPOINT:-am}"
    local client_id="${J_CLIENT_ID:-}"
    local client_secret="${J_CLIENT_SECRET:-}"
    local scopes="${J_SCOPES:-}"
    local shortcode="${J_SHORTCODE:-}"
    local org_id="${J_ORG_ID:-}"

    _expand_short_opts "ecsSCo" "$@"
    set -- "${_EXPANDED[@]}"; unset _EXPANDED

    while [ "$#" -gt 0 ]; do
        case "$1" in
            -e|--endpoint)
                [ -n "${2-}" ] || { _error "-e|--endpoint requires a value. Run \`$SCRIPT_NAME -h\` for usage"; return 2; }
                endpoint="$2"; shift 2 ;;
            --endpoint=*)
                endpoint="${1#*=}"
                [ -n "$endpoint" ] || { _error "-e|--endpoint requires a value. Run \`$SCRIPT_NAME -h\` for usage"; return 2; }
                shift ;;
            -c|--client-id)
                [ -n "${2-}" ] || { _error "-c|--client-id requires a value. Run \`$SCRIPT_NAME -h\` for usage"; return 2; }
                client_id="$2"; shift 2 ;;
            --client-id=*)
                client_id="${1#*=}"
                [ -n "$client_id" ] || { _error "-c|--client-id requires a value. Run \`$SCRIPT_NAME -h\` for usage"; return 2; }
                shift ;;
            -s|--client-secret)
                [ -n "${2-}" ] || { _error "-s|--client-secret requires a value. Run \`$SCRIPT_NAME -h\` for usage"; return 2; }
                client_secret="$2"; shift 2 ;;
            --client-secret=*)
                client_secret="${1#*=}"
                [ -n "$client_secret" ] || { _error "-s|--client-secret requires a value. Run \`$SCRIPT_NAME -h\` for usage"; return 2; }
                shift ;;
            -S|--scopes)
                # -S may be passed "" to explicitly clear J_SCOPES; no empty-value guard
                scopes="$2"; shift 2 ;;
            --scopes=*)
                # --scopes= sets scopes="" intentionally; no empty-value guard
                scopes="${1#*=}"; shift ;;
            -C|--shortcode)
                [ -n "${2-}" ] || { _error "-C|--shortcode requires a value. Run \`$SCRIPT_NAME -h\` for usage"; return 2; }
                shortcode="$2"; shift 2 ;;
            --shortcode=*)
                shortcode="${1#*=}"
                [ -n "$shortcode" ] || { _error "-C|--shortcode requires a value. Run \`$SCRIPT_NAME -h\` for usage"; return 2; }
                shift ;;
            -o|--org-id)
                [ -n "${2-}" ] || { _error "-o|--org-id requires a value. Run \`$SCRIPT_NAME -h\` for usage"; return 2; }
                org_id="$2"; shift 2 ;;
            --org-id=*)
                org_id="${1#*=}"
                [ -n "$org_id" ] || { _error "-o|--org-id requires a value. Run \`$SCRIPT_NAME -h\` for usage"; return 2; }
                shift ;;
            -h|--help) _show_help; return 0 ;;
            *) _error "Unknown argument '$1'. Run \`$SCRIPT_NAME -h\` for usage"; return 2 ;;
        esac
    done

    # Validate endpoint and required parameters before any network call
    # Exit code 2 is reserved for usage errors so callers can distinguish them
    # from runtime/request failures (exit 1)
    case "$endpoint" in
        am)
            if [ -z "$client_id" ]; then
                _error "client_id is required (use -c or J_CLIENT_ID). Run \`$SCRIPT_NAME -h\` for usage"
                return 2
            fi
            if [ -z "$client_secret" ]; then
                _error "client_secret is required (use -s or J_CLIENT_SECRET). Run \`$SCRIPT_NAME -h\` for usage"
                return 2
            fi
            ;;
        slas)
            if [ -z "$client_id" ]; then
                _error "client_id is required (use -c or J_CLIENT_ID). Run \`$SCRIPT_NAME -h\` for usage"
                return 2
            fi
            if [ -z "$client_secret" ]; then
                _error "client_secret is required (use -s or J_CLIENT_SECRET). Run \`$SCRIPT_NAME -h\` for usage"
                return 2
            fi
            if [ -z "$shortcode" ]; then
                _error "shortcode is required for slas (use -C or J_SHORTCODE). Run \`$SCRIPT_NAME -h\` for usage"
                return 2
            fi
            if [ -z "$org_id" ]; then
                _error "org_id is required for slas (use -o or J_ORG_ID). Run \`$SCRIPT_NAME -h\` for usage"
                return 2
            fi
            ;;
        *)
            _error "Invalid --endpoint '$endpoint' (valid: am|slas). Run \`$SCRIPT_NAME -h\` for usage"
            return 2
            ;;
    esac

    # Build token URL
    local token_url
    if [ "$endpoint" = "am" ]; then
        token_url="https://account.demandware.com/dwsso/oauth2/access_token"
    else
        token_url="https://${shortcode}.api.commercecloud.salesforce.com/shopper/auth/v1/organizations/${org_id}/oauth2/token"
    fi

    # Prepare auth header and request body
    local auth_header; auth_header="$(printf '%s:%s' "$client_id" "$client_secret" | base64)"
    local body="grant_type=client_credentials"
    if [ "$scopes" ]; then
        body="${body}&scope=${scopes}"
    fi

    # Request the token
    local response; response="$(curl -s -X POST "$token_url" \
        -H "Content-Type: application/x-www-form-urlencoded" \
        -H "Authorization: Basic $auth_header" -d "$body")"

    local access_token; access_token="$(jq -r .access_token <<< "$response")"
    printf '%s' "$access_token"
)

_client_credentials "$@"
__client_credentials_rc=$?
unset -f _client_credentials
if [ -n "${BASH_SOURCE[0]}" ] && [ "${BASH_SOURCE[0]}" != "$0" ]; then
    eval "unset __client_credentials_rc; return $__client_credentials_rc"
fi
eval "unset __client_credentials_rc; exit $__client_credentials_rc"