# Tests for calc_debt function

test_that("calc_debt works with basic data", {
  set.seed(123)
  years <- 1970:2010

  # Create correlated data with lag
  gdp <- cumsum(rnorm(41, 10, 2))
  invasions <- c(rep(5, 20), 5 + cumsum(rpois(21, lambda = 2)))

  inv_data <- data.frame(year = years, records = invasions)
  driver_data <- data.frame(year = years, gdp = gdp)

  result <- calc_debt(
    invasion_data = inv_data,
    driver_data = driver_data,
    invasion_time_col = "year",
    invasion_count_col = "records",
    driver_time_col = "year",
    driver_col = "gdp",
    lag_years = 10:25
  )

  expect_s3_class(result, "invadebt")
  expect_true(!is.null(result$optimal_lag))
  expect_true(is.data.frame(result$debt_estimate))
})

test_that("calc_debt handles multiple drivers", {
  set.seed(456)
  years <- 1970:2010

  gdp <- cumsum(rnorm(41, 10, 2))
  trade <- cumsum(rnorm(41, 5, 1))
  invasions <- c(rep(5, 20), 5 + cumsum(rpois(21, lambda = 2)))

  inv_data <- data.frame(year = years, records = invasions)
  driver_data <- data.frame(year = years, gdp = gdp, trade = trade)

  result <- calc_debt(
    invasion_data = inv_data,
    driver_data = driver_data,
    invasion_time_col = "year",
    invasion_count_col = "records",
    driver_time_col = "year",
    driver_col = c("gdp", "trade"),
    lag_years = 10:20
  )

  expect_s3_class(result, "invadebt")
  expect_true(nrow(result$correlations) > 0)
})

test_that("calc_debt handles missing columns", {
  inv_data <- data.frame(year = 1:10, records = 1:10)
  driver_data <- data.frame(year = 1:10, gdp = 1:10)

  expect_error(
    calc_debt(inv_data, driver_data,
              invasion_time_col = "bad_col",
              invasion_count_col = "records",
              driver_time_col = "year",
              driver_col = "gdp"),
    "not found"
  )
})