suppressPackageStartupMessages(library(dplyr))

simulate_icu_cohort <- function(n_patients = 1000, seed = 20260531) {
  set.seed(seed)

  tibble(
    patient_id = seq_len(n_patients),

    age = round(rnorm(n_patients, mean = 65, sd = 14)) |>
      pmin(95) |>
      pmax(18),

    sex = sample(c("female", "male"), size = n_patients, replace = TRUE, prob = c(0.45, 0.55)),

    sofa_score = rpois(n_patients, lambda = 7) |>
      pmin(20),

    lactate = round(rlnorm(n_patients, meanlog = log(3), sdlog = 0.5), 1) |>
      pmin(15),

    map = round(rnorm(n_patients, mean = 62, sd = 10)) |>
      pmin(95) |>
      pmax(35),

    suspected_sepsis = rbinom(n_patients, size = 1, prob = 0.90)
  ) |>
    mutate(
      hypotension_at_baseline = as.integer(map < 65),
      elevated_lactate_at_baseline = as.integer(lactate >= 2),
      eligible = as.integer(
        suspected_sepsis == 1 &
          hypotension_at_baseline == 1 &
          elevated_lactate_at_baseline == 1
      ),
      severity_score = 0.04 * (age - 65) +
        0.18 * (sofa_score - 7) +
        0.25 * (lactate - 3) -
        0.04 * (map - 62),
      prob_early_vasopressor = plogis(-0.2 + severity_score),
      early_vasopressor = rbinom(n(), size = 1, prob = prob_early_vasopressor),
      time_to_vasopressor_hours = ifelse(
        early_vasopressor == 1,
        runif(n(), min = 0, max = 2),
        runif(n(), min = 2, max = 24)
      ) |>
        round(2),
      mortality_linear_predictor = -1.4 +
        0.03 * (age - 65) +
        0.20 * (sofa_score - 7) +
        0.28 * (lactate - 3) -
        0.05 * (map - 62) -
        0.25 * early_vasopressor,
      prob_death_28d = plogis(mortality_linear_predictor),
      death_28d = rbinom(n(), size = 1, prob = prob_death_28d)
    ) |>
    select(
      patient_id,
      age,
      sex,
      sofa_score,
      lactate,
      map,
      suspected_sepsis,
      hypotension_at_baseline,
      elevated_lactate_at_baseline,
      eligible,
      early_vasopressor,
      time_to_vasopressor_hours,
      death_28d
    )
}