# Test for delay density passed to cfr_*()
test_that("CFR functions work with delay_density as lambda", {
  # Checks pass and cfr_static function works
  ddens <- function(x) stats::dgamma(x, 5, 1)
  expect_no_condition(
    cfr_static(ebola1976, delay_density = ddens)
  )
  expect_no_condition(
    cfr_rolling(ebola1976, delay_density = ddens)
  )
  expect_no_condition(
    cfr_time_varying(ebola1976, delay_density = ddens)
  )
  expect_no_condition(
    estimate_ascertainment(
      ebola1976,
      delay_density = ddens, severity_baseline = 0.7
    )
  )
})

test_that("CFR functions work with delay_density as <distcrete>", {
  # guarding against CRAN noSuggests checks
  skip_if_not_installed("distcrete")
  # Checks pass and cfr_static function works with disctcrete
  ddens <- distcrete::distcrete("gamma", 1, shape = 2.4, scale = 3.33)$d
  expect_no_condition(
    cfr_static(ebola1976, delay_density = ddens)
  )
  expect_no_condition(
    cfr_rolling(ebola1976, delay_density = ddens)
  )
  expect_no_condition(
    cfr_time_varying(ebola1976, delay_density = ddens)
  )
  expect_no_condition(
    estimate_ascertainment(
      ebola1976,
      delay_density = ddens, severity_baseline = 0.7
    )
  )
})

# Test error cases
msg <- "(`delay_density` must be)*(function)*(evaluating distribution density)"

test_that("Input checking on delay_density works", {
  # Checks fail on badly specified delay_density fns

  # Function returns NULL
  ddens <- function(x) NULL
  expect_error(
    cfr_static(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_rolling(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_time_varying(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    estimate_ascertainment(
      ebola1976,
      delay_density = ddens, severity_baseline = 0.7
    ),
    regexp = msg
  )

  # Function returns non-numeric
  # NOTE the use of seq_along - there are no checks that the fn
  # is statistically correct or a valid density function
  ddens <- function(x) as.character(seq_along(x))
  expect_error(
    cfr_static(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_rolling(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_time_varying(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    estimate_ascertainment(
      ebola1976,
      delay_density = ddens, severity_baseline = 0.7
    ),
    regexp = msg
  )

  # Function returns Inf
  ddens <- function(x) rep(Inf, times = length(x))
  expect_error(
    cfr_static(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_rolling(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_time_varying(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    estimate_ascertainment(
      ebola1976,
      delay_density = ddens, severity_baseline = 0.7
    ),
    regexp = msg
  )

  # Function returns negative values
  # NOTE the use of seq_along - there are no checks that the fn
  # is statistically correct or a valid density function
  ddens <- function(x) -seq_along(x)
  expect_error(
    cfr_static(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_rolling(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_time_varying(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    estimate_ascertainment(
      ebola1976,
      delay_density = ddens, severity_baseline = 0.7
    ),
    regexp = msg
  )

  # Function returns NAs
  # NOTE the use of seq_along - there are no checks that the fn
  # is statistically correct or a valid density function
  ddens <- function(x) {
    y <- seq_along(x)
    y[1] <- NA_real_
  }
  expect_error(
    cfr_static(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_rolling(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_time_varying(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    estimate_ascertainment(
      ebola1976,
      delay_density = ddens, severity_baseline = 0.7
    ),
    regexp = msg
  )

  # Function returns wrong length
  # NOTE the use of seq_along - there are no checks that the fn
  # is statistically correct or a valid density function
  ddens <- function(x) {
    head(seq_along(x))
  }
  expect_error(
    cfr_static(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_rolling(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    cfr_time_varying(ebola1976, delay_density = ddens),
    regexp = msg
  )
  expect_error(
    estimate_ascertainment(
      ebola1976,
      delay_density = ddens, severity_baseline = 0.7
    ),
    regexp = msg
  )
})

#### Checks on test_fn_req_args() ####
test_that("Functions to test delay density work", {
  # Test function to check number of required arguments
  expect_true(
    test_fn_req_args(
      function(x) dgamma(x, 5, 1)
    )
  )
  expect_false(
    test_fn_req_args(
      dgamma
    )
  )
  expect_false(
    test_fn_req_args(
      function(x, y, ...) dgamma(x, 5, 1, ...) + y
    )
  )
  expect_true(
    test_fn_req_args(
      dgamma, 2
    )
  )
  # expect TRUE when an appropriate primitive is passed
  # NOTE: Passes as this primitive has one arg
  expect_true(
    test_fn_req_args(is.list)
  )
  expect_false(
    test_fn_req_args(`+`)
  )

  # distcrete
  ddens <- distcrete::distcrete("gamma", 1, shape = 5, scale = 1)$d
  expect_true(
    test_fn_req_args(
      ddens
    )
  )

  # functions with ellipsis
  expect_true(
    test_fn_req_args(
      function(x, ...) dgamma(x, 5, 1, ...)
    )
  )

  # Test function to check for numeric output
  expect_true(
    test_fn_num_out(
      function(x) dgamma(x, 5, 1)
    )
  )
  expect_true(
    test_fn_num_out(
      ddens
    )
  )
  expect_false(
    test_fn_num_out(
      function(x, ...) as.character(dgamma(x, 5, 1, ...))
    )
  )
})