#This script contains functions to start the simulation


#'run_simulation
#'@description Calls OGS6 object validator functions, exports all necessary files and starts OpenGeoSys6
#'@param ogs6_obj A OGS6 class object
#'@param iter_n The number of iterations (for simulation chains)
#'@param output_to_log_file Should the output be written to a log file?
#'@export
run_simulation <- function(ogs6_obj, iter_n = 1, output_to_log_file = TRUE) {

    assertthat::assert_that(inherits(ogs6_obj, "OGS6"))
    assertthat::assert_that(is.numeric(iter_n), iter_n > 0, iter_n < 500)

    #Call all validators
    validate_all(ogs6_obj)

    #Export the simulation files
    export_gml(ogs6_obj)
    export_prj(ogs6_obj)

    #Direct simulation output to log file
    if(output_to_log_file){
        log_file <- paste0(ogs6_obj$sim_path, ogs6_obj$sim_name, "_log.txt")
        #Write to file...
    }

    #Run simulations (and read in output as input)
    for(i in seq_len(iter_n)){

        #Call OGS6
        system(command = paste0(ogs6_obj$ogs_bin_path, "ogs.exe ",
                                ogs6_obj$sim_path, ogs6_obj$sim_name, ".prj -o ",
                                ogs6_obj$sim_path))

        # read_in_output(ogs6_obj)
    }

    closeAllConnections()
}


#============================== VALIDATION UTILITY ================================


#'validate_all
#'@description Validates all necessary parameters
#'@param ogs6_obj A OGS6 class object
validate_all <- function(ogs6_obj) {

    if(!ogs6_obj$get_status()){
        stop("There are some components missing from your OGS6 object.", call. = FALSE)
    }

    if(is.null(ogs6_obj$gml)){
        if(length(ogs6_obj$meshes) < 2){
            stop("If you don't want to specify a gml object, you must have multiple
                      meshes. You can define more by calling the function generate_structured_mesh.", call. = FALSE)
        }
    }else if(length(ogs6_obj$meshes) != 1){
        stop("If you want to specify a gml object, there must be only one mesh (one vtk file).", call. = FALSE)
    }

    #...
}


#'validate_paths
#'@description Helper function to pull path validation out of already large class OGS6
#'@param sim_path The path where all relevant files for the simulation will be saved
#'@param ogs_bin_path Path to OpenGeoSys6 /bin directory
validate_paths <- function(sim_path, ogs_bin_path){
    if(!dir.exists(sim_path)){
        dir.create(sim_path)
    }else{
        if(length(dir(sim_path, all.files = TRUE)) != 0){
            warning(paste0("The sim_path directory you defined ('", sim_path,
                           "') already exists (that is ok). However, ",
                           "it is not empty. Files may be overwritten."), call. = FALSE)
        }
    }

    if(!file.exists(paste0(ogs_bin_path, "generateStructuredMesh.exe"))) {
        stop(paste("Could not find executable file generateStructuredMesh.exe at location",
                   ogs_bin_path), call. = FALSE)
    }
}


#'read_in_output
#'@description After a OGS6 simulation was run, reads in the generated .vtu files as new input for
#' the .prj file
#'@param ogs6_obj A OGS6 class object
read_in_output <- function(ogs6_obj) {

    #....WIP
}