#!/usr/bin/env bash
# tail_journal — wrapper sobre journalctl con formato consistente

tail_journal() {
    local unit="${1:-}"
    local lines="${2:-100}"
    local follow="${3:-false}"
    local since="${4:-}"
    local priority="${5:-info}"

    if [[ -z "$unit" ]]; then
        echo "tail_journal: unit requerida" >&2
        return 1
    fi

    # Normalizar nombre de unit (añadir .service si no tiene extension)
    local unit_full="$unit"
    if [[ "$unit" != *.* ]]; then
        unit_full="${unit}.service"
    fi

    # Validar prioridad
    case "$priority" in
        emerg|alert|crit|err|warning|notice|info|debug) ;;
        *)
            echo "tail_journal: prioridad invalida '$priority'. Valores: emerg alert crit err warning notice info debug" >&2
            return 2
            ;;
    esac

    # Verificar que journalctl esta disponible
    if ! command -v journalctl &>/dev/null; then
        echo "tail_journal: journalctl no disponible" >&2
        return 5
    fi

    # Detectar si la unit es de usuario o de sistema
    local user_flag=""
    if systemctl --user list-units --all 2>/dev/null | grep -q "$unit_full"; then
        user_flag="--user"
    fi

    # Construir comando base
    local -a cmd
    if [[ -z "$user_flag" ]]; then
        cmd=(sudo journalctl)
    else
        cmd=(journalctl --user)
    fi

    cmd+=(-u "$unit_full" -n "$lines" -p "$priority" --output=short-iso)

    if [[ -n "$since" ]]; then
        cmd+=(--since "$since")
    fi

    local follow_flag=false
    if [[ "$follow" == "true" || "$follow" == "-f" ]]; then
        follow_flag=true
        cmd+=(-f)
    fi

    # Verificar que la unit existe (solo si no hay user_flag y no es sudo)
    if [[ -n "$user_flag" ]]; then
        if ! systemctl --user list-units --all 2>/dev/null | grep -q "$unit_full"; then
            echo "tail_journal: unit '$unit_full' no encontrada" >&2
            return 1
        fi
    fi

    # Ejecutar sin bufferizar si follow=true
    if [[ "$follow_flag" == "true" ]]; then
        stdbuf -oL "${cmd[@]}"
    else
        "${cmd[@]}"
    fi
}