#!/bin/sh
# sysadminctl — macOS user management stub for Darling
#
# Translates macOS sysadminctl commands to direct /etc/passwd file operations.
# Only implements the subset needed by the Nix installer:
#
#   sysadminctl -addUser <name> [-UID <uid>] [-GID <gid>]
#               [-home <dir>] [-shell <shell>] [-fullName <name>]
#   sysadminctl -deleteUser <name>
#
# This stub operates on the Darling prefix's /etc/passwd file, NOT the host's.
#
# See: plan/07-phase5-daemon.md (Task 5.1)

set -eu

PASSWD_FILE="/etc/passwd"

# ── Helpers ─────────────────────────────────────────────────────────────────

errcho() {
    echo "$@" >&2
}

usage() {
    errcho "Usage: sysadminctl -addUser <username> [-UID <uid>] [-GID <gid>]"
    errcho "                   [-home <homedir>] [-shell <shell>] [-fullName <gecos>]"
    errcho "       sysadminctl -deleteUser <username>"
    errcho ""
    errcho "Options:"
    errcho "  -addUser <name>      Create a new user"
    errcho "  -deleteUser <name>   Delete an existing user"
    errcho "  -UID <uid>           User ID (numeric)"
    errcho "  -GID <gid>           Primary group ID (numeric)"
    errcho "  -home <dir>          Home directory (default: /var/empty)"
    errcho "  -shell <shell>       Login shell (default: /usr/bin/false)"
    errcho "  -fullName <gecos>    Full name / GECOS field"
    errcho "  -password <pass>     Password (ignored — always set to locked)"
    errcho "  -adminUser <user>    Admin user for authentication (ignored)"
    errcho "  -adminPassword <pw>  Admin password (ignored)"
    exit 64
}

# user_exists <name> — exit 0 if the user exists in /etc/passwd
user_exists() {
    grep -q "^${1}:" "$PASSWD_FILE" 2>/dev/null
}

# uid_exists <uid> — exit 0 if the UID is already taken
uid_exists() {
    awk -F: -v uid="$1" '$3 == uid { found=1; exit } END { exit !found }' "$PASSWD_FILE" 2>/dev/null
}

# get_uid_owner <uid> — print the username that owns this UID
get_uid_owner() {
    awk -F: -v uid="$1" '$3 == uid { print $1; exit }' "$PASSWD_FILE"
}

# next_uid — find the next available UID >= 300 (Nix build user range)
next_uid() {
    awk -F: '{ if ($3 >= 300 && $3 > max) max = $3 } END { print (max ? max + 1 : 300) }' "$PASSWD_FILE"
}

# ── Argument parsing ────────────────────────────────────────────────────────

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

ACTION=""
USERNAME=""

case "$1" in
    -addUser)
        ACTION="add"
        USERNAME="$2"
        shift 2
        ;;
    -deleteUser)
        ACTION="delete"
        USERNAME="$2"
        shift 2
        ;;
    -h|--help|-help)
        usage
        ;;
    *)
        errcho "sysadminctl: unknown option '$1'"
        usage
        ;;
esac

# Validate username (alphanumeric, underscore, dash, dot; max 256 chars)
case "$USERNAME" in
    "")
        errcho "sysadminctl: username must not be empty"
        exit 1
        ;;
    *[!a-zA-Z0-9_.-]*)
        errcho "sysadminctl: invalid username '$USERNAME' (allowed: a-z A-Z 0-9 _ . -)"
        exit 1
        ;;
esac

if [ "${#USERNAME}" -gt 256 ]; then
    errcho "sysadminctl: username too long (max 256 characters)"
    exit 1
fi

# ── addUser ─────────────────────────────────────────────────────────────────

if [ "$ACTION" = "add" ]; then
    UID_VAL=""
    GID_VAL=""
    HOME_DIR="/var/empty"
    SHELL="/usr/bin/false"
    GECOS=""

    while [ "$#" -gt 0 ]; do
        case "$1" in
            -UID)
                [ "$#" -ge 2 ] || { errcho "sysadminctl: -UID requires an argument"; exit 1; }
                UID_VAL="$2"
                shift 2
                ;;
            -GID)
                [ "$#" -ge 2 ] || { errcho "sysadminctl: -GID requires an argument"; exit 1; }
                GID_VAL="$2"
                shift 2
                ;;
            -home)
                [ "$#" -ge 2 ] || { errcho "sysadminctl: -home requires an argument"; exit 1; }
                HOME_DIR="$2"
                shift 2
                ;;
            -shell)
                [ "$#" -ge 2 ] || { errcho "sysadminctl: -shell requires an argument"; exit 1; }
                SHELL="$2"
                shift 2
                ;;
            -fullName)
                [ "$#" -ge 2 ] || { errcho "sysadminctl: -fullName requires an argument"; exit 1; }
                GECOS="$2"
                shift 2
                ;;
            -password)
                # Ignored — we always set the password field to 'x' (locked)
                [ "$#" -ge 2 ] || { errcho "sysadminctl: -password requires an argument"; exit 1; }
                shift 2
                ;;
            -adminUser|-admin)
                # Ignored — no authentication needed in a Darling prefix
                [ "$#" -ge 2 ] || { errcho "sysadminctl: $1 requires an argument"; exit 1; }
                shift 2
                ;;
            -adminPassword)
                # Ignored — no authentication needed in a Darling prefix
                [ "$#" -ge 2 ] || { errcho "sysadminctl: -adminPassword requires an argument"; exit 1; }
                shift 2
                ;;
            -roleAccount)
                # Boolean flag used by newer Nix installers — no argument
                shift
                ;;
            *)
                errcho "sysadminctl: unknown option '$1'"
                usage
                ;;
        esac
    done

    # Idempotent: if user already exists, succeed silently
    if user_exists "$USERNAME"; then
        echo "User '$USERNAME' already exists"
        exit 0
    fi

    # Assign UID if not specified
    if [ -z "$UID_VAL" ]; then
        UID_VAL=$(next_uid)
    fi

    # Validate UID is numeric
    case "$UID_VAL" in
        *[!0-9]*)
            errcho "sysadminctl: UID must be numeric, got '$UID_VAL'"
            exit 1
            ;;
    esac

    # Check for UID conflicts
    if uid_exists "$UID_VAL"; then
        existing=$(get_uid_owner "$UID_VAL")
        errcho "sysadminctl: UID $UID_VAL already in use by user '$existing'"
        exit 1
    fi

    # Default GID to 0 (wheel/root) if not specified
    if [ -z "$GID_VAL" ]; then
        GID_VAL=0
    fi

    # Validate GID is numeric
    case "$GID_VAL" in
        *[!0-9]*)
            errcho "sysadminctl: GID must be numeric, got '$GID_VAL'"
            exit 1
            ;;
    esac

    # Ensure /etc/passwd exists
    if [ ! -f "$PASSWD_FILE" ]; then
        errcho "sysadminctl: $PASSWD_FILE does not exist"
        exit 1
    fi

    # Ensure the home directory's parent exists (but don't create the home
    # directory itself — Nix build users use /var/empty which should already
    # exist).
    HOME_PARENT=$(dirname "$HOME_DIR")
    if [ ! -d "$HOME_PARENT" ] && [ "$HOME_PARENT" != "/" ]; then
        mkdir -p "$HOME_PARENT" 2>/dev/null || true
    fi

    # Create the passwd entry
    # Format: name:password:UID:GID:GECOS:home:shell
    echo "${USERNAME}:x:${UID_VAL}:${GID_VAL}:${GECOS}:${HOME_DIR}:${SHELL}" >> "$PASSWD_FILE"

    echo "Created user '$USERNAME' (UID=$UID_VAL, GID=$GID_VAL, home=$HOME_DIR, shell=$SHELL)"
    exit 0
fi

# ── deleteUser ──────────────────────────────────────────────────────────────

if [ "$ACTION" = "delete" ]; then
    # Consume any remaining flags (some callers pass -secure, etc.)
    while [ "$#" -gt 0 ]; do
        case "$1" in
            -secure|-keepHome|-adminUser|-adminPassword)
                # Ignored — these are macOS-specific options
                if [ "$1" = "-adminUser" ] || [ "$1" = "-adminPassword" ]; then
                    shift 2 2>/dev/null || shift
                else
                    shift
                fi
                ;;
            *)
                errcho "sysadminctl: unknown option '$1' (ignoring)"
                shift
                ;;
        esac
    done

    # Idempotent: if user doesn't exist, succeed silently
    if ! user_exists "$USERNAME"; then
        echo "User '$USERNAME' does not exist"
        exit 0
    fi

    # Remove the user from /etc/passwd
    TMPFILE=$(mktemp "${PASSWD_FILE}.XXXXXX")
    grep -v "^${USERNAME}:" "$PASSWD_FILE" > "$TMPFILE" || true
    mv "$TMPFILE" "$PASSWD_FILE"

    echo "Deleted user '$USERNAME'"
    exit 0
fi

# Should not reach here
errcho "sysadminctl: internal error — unknown action '$ACTION'"
exit 1