library(testthat)
library(BioMixModel)


# ---------------------------------------------------------
# formulas must be a list
# ---------------------------------------------------------

test_that("multivariate model validates formulas as a list", {
  
  skip_if_not_installed("brms")
  
  dat <- data.frame(
    y1 = rnorm(10),
    y2 = rnorm(10),
    x = rnorm(10)
  )
  
  expect_error(
    fit_multivariate(
      formulas = y1 ~ x,
      data = dat
    ),
    "'formulas' must be a list"
  )
})


# ---------------------------------------------------------
# at least two formulas required
# ---------------------------------------------------------

test_that("multivariate model requires at least two formulas", {
  
  skip_if_not_installed("brms")
  
  dat <- data.frame(
    y1 = rnorm(10),
    y2 = rnorm(10),
    x = rnorm(10)
  )
  
  expect_error(
    fit_multivariate(
      formulas = list(y1 ~ x),
      data = dat
    ),
    "At least two model formulas are required"
  )
})


# ---------------------------------------------------------
# all elements must be formulas
# ---------------------------------------------------------

test_that("multivariate model validates individual formulas", {
  
  skip_if_not_installed("brms")
  
  dat <- data.frame(
    y1 = rnorm(10),
    y2 = rnorm(10),
    x = rnorm(10)
  )
  
  expect_error(
    fit_multivariate(
      formulas = list(
        y1 ~ x,
        "y2 ~ x"
      ),
      data = dat
    ),
    "All elements of 'formulas' must be model formulas"
  )
})


# ---------------------------------------------------------
# data must be a data frame
# ---------------------------------------------------------

test_that("multivariate model validates data", {
  
  skip_if_not_installed("brms")
  
  expect_error(
    fit_multivariate(
      formulas = list(
        y1 ~ x,
        y2 ~ x
      ),
      data = list(
        y1 = rnorm(10),
        y2 = rnorm(10),
        x = rnorm(10)
      )
    ),
    "data must be a data frame"
  )
})

test_that("multivariate mixed model fits successfully", {
  
  skip_if_not_installed("brms")
  skip_on_cran()
  set.seed(123)
  
  dat <- data.frame(
    id = factor(rep(1:5, each = 4)),
    x = rep(1:4, 5)
  )
  
  dat$y1 <- 5 + 2 * dat$x +
    rnorm(20) +
    rnorm(5)[dat$id]
  
  dat$y2 <- 10 - dat$x +
    rnorm(20) +
    rnorm(5)[dat$id]
  
  m <- suppressWarnings(
    fit_multivariate(
      formulas = list(
        y1 ~ x + (1 | id),
        y2 ~ x + (1 | id)
      ),
      data = dat,
      chains = 1,
      iter = 100,
      warmup = 50,
      refresh = 0
    )
  )
  
  expect_s3_class(m, "biomix_multivariate")
  expect_s3_class(m, "biomix")
  expect_true(is.list(m))
  
  expect_true(inherits(m$fit, "brmsfit"))
  
  expect_equal(
    m$model_type,
    "Multivariate mixed model"
  )
  
  expect_equal(
    length(m$formulas),
    2
  )
  
  expect_identical(
    m$data,
    dat
  )
})

test_that("multivariate model stores supplied components", {
  
  skip_if_not_installed("brms")
  skip_on_cran()
  set.seed(456)
  
  dat <- data.frame(
    y1 = rnorm(20),
    y2 = rnorm(20),
    x = rnorm(20)
  )
  
  formulas <- list(
    y1 ~ x,
    y2 ~ x
  )
  
  m <- suppressWarnings(
    fit_multivariate(
      formulas = formulas,
      data = dat,
      chains = 1,
      iter = 100,
      warmup = 50,
      refresh = 0
    )
  )
  
  expect_equal(m$formulas, formulas)
  expect_identical(m$data, dat)
  expect_equal(
    m$model_type,
    "Multivariate mixed model"
  )
})

test_that("multivariate model rejects empty formula list", {
  
  skip_if_not_installed("brms")
  
  dat <- data.frame(
    y1 = rnorm(10),
    y2 = rnorm(10),
    x = rnorm(10)
  )
  
  expect_error(
    fit_multivariate(
      formulas = list(),
      data = dat
    ),
    "At least two model formulas are required"
  )
})