# Parameters: read the YAML, then apply a world and a truth scenario as overrides.

#' Recursively merge `override` into `base` (lists only; scalars replace).
deep_merge <- function(base, override) {
  for (nm in names(override)) {
    if (is.list(override[[nm]]) && is.list(base[[nm]])) {
      base[[nm]] <- deep_merge(base[[nm]], override[[nm]])
    } else {
      base[[nm]] <- override[[nm]]
    }
  }
  base
}

#' Path of the default parameter file, inside the installed or loaded package.
default_params_path <- function() {
  p <- system.file("params", "dgp_default.yml", package = "pvisim")
  if (p == "") stop("dgp_default.yml not found; load the package with pkgload::load_all('pvisim')")
  p
}

#' Load parameters for one world and one truth scenario.
#'
#' @param world name in `worlds:` (W0, W1, W1_rho0, W2, W3, W4, W5, WR).
#' @param scenario name in `scenarios:` (null, harm, benefit_harm).
#' @param path YAML file; defaults to the package's dgp_default.yml.
#' @param overrides optional list merged last (used by calibration and tests).
#' @param calibrated apply the world's entry in `calibration_file` (intercepts solved by
#'   simulations/01_calibrate.R under the null scenario), after the world and before the
#'   scenario. Calibration itself runs with FALSE.
load_params <- function(world = "W0", scenario = "null", path = default_params_path(),
                        overrides = NULL, calibrated = TRUE,
                        calibration_file = "simulations/config/calibrated.yml") {
  raw <- yaml::read_yaml(path)
  if (!world %in% names(raw$worlds)) stop("unknown world: ", world)
  if (!scenario %in% names(raw$scenarios)) stop("unknown scenario: ", scenario)
  par <- raw[setdiff(names(raw), c("worlds", "scenarios"))]
  par <- deep_merge(par, raw$worlds[[world]])
  if (calibrated && file.exists(calibration_file)) {
    cal <- yaml::read_yaml(calibration_file)[[world]]
    if (!is.null(cal)) par <- deep_merge(par, cal)
    par$calibrated <- !is.null(cal)
  } else {
    par$calibrated <- FALSE
  }
  par <- deep_merge(par, raw$scenarios[[scenario]])
  if (!is.null(overrides)) par <- deep_merge(par, overrides)
  par$world <- world
  par$scenario <- scenario
  par
}