test_that("meridional conversion works", {
  u <- c(1, 0, -1, 0)
  v <- c(0, 1, 0, -1)
  m <- cbind(u, v)
  res <- data.frame(wspd = 1, wdir = c(270, 180, 90, 0))

  expect_equal(zmcomp2metconv(m), res)
  expect_equal(zmcomp2metconv(u, v), res)
})


test_that("metconv2zmcomp returns correct components for cardinal winds", {
  # North wind (10 m/s) → blows southward → u = 0, v = -10
  res <- metconv2zmcomp(10, 0)
  expect_equal(res$u, 0, tolerance = 1e-12)
  expect_equal(res$v, -10, tolerance = 1e-12)

  # East wind (5 m/s) → blows westward → u = -5, v = 0
  res <- metconv2zmcomp(5, 90)
  expect_equal(res$u, -5, tolerance = 1e-12)
  expect_equal(res$v, 0, tolerance = 1e-12)

  # South wind (8 m/s) → blows northward → u = 0, v = +8
  res <- metconv2zmcomp(8, 180)
  expect_equal(res$u, 0, tolerance = 1e-12)
  expect_equal(res$v, 8, tolerance = 1e-12)

  # West wind (12 m/s) → blows eastward → u = +12, v = 0
  res <- metconv2zmcomp(12, 270)
  expect_equal(res$u, 12, tolerance = 1e-12)
  expect_equal(res$v, 0, tolerance = 1e-12)
})

test_that("metconv2zmcomp works with vector inputs", {
  spd <- c(10, 5, 8, 12)
  dir <- c(0, 90, 180, 270)
  res <- metconv2zmcomp(spd, dir)

  expect_equal(nrow(res), 4)
  expect_equal(res$u, c(0, -5, 0, 12), tolerance = 1e-12)
  expect_equal(res$v, c(-10, 0, 8, 0), tolerance = 1e-12)
})

test_that("%nin% helper works", {
  expect_false(1 %nin% c(1, 3, 5, 9))
  expect_true(1 %nin% c(3, 5, 9))
})

test_that("Fast trapz works", {
  n <- 101
  x <- seq(0, pi, length.out = n)
  y1 <- sin(matrix(x, ncol = n, nrow = n, byrow = FALSE))
  y2 <- sin(matrix(x, ncol = n, nrow = n, byrow = TRUE))
  expect_equal(fastTrapz(x, y1, 1), t(fastTrapz(x, y2, 2)))
})

test_that("JONSWAP computation works", {
  expect_vector(jonswap())
  expect_vector(jonswap(hs = 1, tp = 15))
  expect_snapshot_output(jonswap())
  expect_snapshot_output(jonswap(fmax = 0.95, df = 0.003))
  expect_error(jonswap(hs = 4, tp = 15, fmax = 0.95))
  expect_error(jonswap(gam = 0.5))
})

test_that("Directional means are accurately computed", {
  expect_error(mean_direction())
  expect_equal(mean_direction(rep(0, 10)), 0)
  expect_equal(mean_direction(rep(0, 10)), mean_direction(rep(360, 10)))
  expect_error(mean_direction("one"), "'directions' must be numeric")
  expect_error(mean_direction(1:2, c("one", "two")), "'weights' must be numeric")
})

test_that("Weighted directional means are accurately computed", {
  expect_warning(mean_direction(c(0, 90), weights = c(-1, 1)))
  expect_error(mean_direction(c(0, 90), weights = c(1)))
  expect_equal(mean_direction(c(0, 90), weights = c(50, 50)), 45)
  expect_equal(mean_direction(c(0, 90), weights = c(0, 1)), 90)
  expect_equal(mean_direction(directions = numeric(0)), numeric(0))
})

test_that("Directional binning works", {
  expect_error(cut_directions("one"), "'directions' must be numeric")
  expect_error(cut_directions(1, 1), "'n_bins' must be at least 2")
  expect_equal(cut_directions(numeric()), numeric())
  expect_equal(
    cut_directions(c(10, 80, 170, 280), n_bins = 4),
    factor(c("N", "E", "S", "W"), levels = c("N", "E", "S", "W"))
  )
  expect_equal(
    cut_directions(c(10, 80, 170, 280), n_bins = 8),
    factor(
      c("N", "E", "S", "W"),
      levels = c("N", "NE", "E", "SE", "S", "SW", "W", "NW")
    )
  )
  expect_equal(
    cut_directions(c(10, 80, 170, 280), n_bins = 16),
    factor(
      c("N", "E", "S", "W"),
      levels = c(
        "N",
        "NNE",
        "NE",
        "ENE",
        "E",
        "ESE",
        "SE",
        "SSE",
        "S",
        "SSW",
        "SW",
        "WSW",
        "W",
        "WNW",
        "NW",
        "NNW"
      )
    )
  )
})