library(acousticTS)

test_that("elastic-shell modal interfaces agree across frequencies", {
  frequency <- c(12000, 38000, 70000)
  ka <- acousticTS:::.calculate_ka_matrix(
    frequency,
    sound_speed_sw = 1477.3,
    sound_speed_fluid = 1575,
    sound_speed_longitudinal = 5600,
    sound_speed_transversal = 3200,
    radius_shell = 0.01,
    radius_fluid = 0.009
  )
  density <- 2565
  mu <- density * 3200^2
  lambda <- density * 5600^2 - 2 * mu
  limits <- c(2L, 4L, 6L)
  actual <- acousticTS:::elastic_shell_boundary_conditions(
    ka,
    limits,
    lambda,
    mu,
    1026.8 / density,
    1077.3 / density
  )
  reference <- acousticTS:::elastic_shell_boundary_conditions_old(
    ka[1, ],
    ka[2, ],
    ka[3, ],
    ka[6, ],
    ka[5, ],
    ka[7, ],
    0:6,
    lambda,
    mu,
    1026.8 / density,
    1077.3 / density
  )
  for (i in seq_along(frequency)) {
    retained <- seq_len(limits[i] + 1L)
    expect_equal(actual[i, retained], reference[i, retained], tolerance = 1e-12)
    if (limits[i] < 6) {
      expect_true(all(is.na(actual[i, -(retained)])))
    }
  }
})

compute_essms_modal_coeffs <- function(density_fluid, sound_speed_fluid) {
  object <- ess_generate(
    shape = sphere(radius_body = 0.01, n_segments = 80),
    radius_shell = 0.01,
    shell_thickness = 0.0008,
    density_shell = 2565,
    sound_speed_shell = 3750,
    density_fluid = density_fluid,
    sound_speed_fluid = sound_speed_fluid,
    E = 7.0e10,
    nu = 0.32
  )

  object <- essms_initialize(
    object,
    frequency = 38e3,
    sound_speed_sw = 1477.3,
    density_sw = 1026.8,
    m_limit = 8L
  )

  model <- extract(object, "model_parameters")$ESSMS
  shell <- model$shell
  fluid <- model$fluid
  acoustics <- model$parameters$acoustics

  sound_speed_longitudinal <- sqrt((shell$lambda + 2 * shell$G) / shell$density)
  sound_speed_transversal <- sqrt(shell$G / shell$density)

  ka_matrix <- .calculate_ka_matrix(
    frequency = acoustics$frequency,
    sound_speed_sw = model$medium$sound_speed,
    sound_speed_fluid = fluid$sound_speed,
    sound_speed_longitudinal = sound_speed_longitudinal,
    sound_speed_transversal = sound_speed_transversal,
    radius_shell = shell$radius,
    radius_fluid = fluid$radius
  )

  as.vector(
    elastic_shell_boundary_conditions(
      ka_matrix = ka_matrix,
      m_limit = acoustics$m_limit,
      lambda = shell$lambda,
      mu = shell$G,
      rho_ratio_sw = model$medium$density / shell$density,
      rho_ratio_fl = fluid$density / shell$density
    )[1L, ]
  )
}

test_that(
  "ESSMS shell coefficients respond to the Stanton fluid generalization",
  {
    coeff_equal_fluids <- compute_essms_modal_coeffs(
      density_fluid = 1026.8,
      sound_speed_fluid = 1477.3
    )
    coeff_contrasted_fluids <- compute_essms_modal_coeffs(
      density_fluid = 1077.3,
      sound_speed_fluid = 1575
    )

    expect_false(
      isTRUE(all.equal(
        coeff_equal_fluids,
        coeff_contrasted_fluids,
        tolerance = 1e-8
      ))
    )

    expect_true(all(is.finite(Mod(coeff_equal_fluids))))
    expect_true(all(is.finite(Mod(coeff_contrasted_fluids))))
  }
)