// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: 2026 Martino Ferrari

#include "harness.hpp"

#include <plot/math/transform.hpp>

using plot::Transform;

PLOT_TEST(linear_round_trip) {
  Transform t{2.0, 10.0, 3.0, -1.0, false, false};
  PLOT_CHECK_NEAR(t.to_screen_x(0.0), 10.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_screen_x(5.0), 20.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_data_x(20.0), 5.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_data_y(t.to_screen_y(7.5)), 7.5, 1e-12);
}

PLOT_TEST(log_x_round_trip) {
  Transform t{100.0, 0.0, 1.0, 0.0, true, false};
  PLOT_CHECK_NEAR(t.to_screen_x(1.0), 0.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_screen_x(10.0), 100.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_data_x(100.0), 10.0, 1e-9);
}

PLOT_TEST(zoom_anchor_is_invariant) {
  // Anchoring a zoom at a data coordinate must leave that coordinate's screen
  // position unchanged.
  Transform t{1.0, 0.0, 1.0, 0.0, false, false};
  const double anchor_data = 3.25;
  const double before = t.to_screen_x(anchor_data);
  t.sx *= 4.0;
  t.tx = before - anchor_data * t.sx;
  PLOT_CHECK_NEAR(t.to_screen_x(anchor_data), before, 1e-12);
}
PLOT_TEST(from_range_linear) {
  const Transform t =
      Transform::from_range({0.0, 10.0}, {-1.0, 1.0}, 0.0, 100.0, 0.0, 200.0, false, false);
  PLOT_CHECK_NEAR(t.to_screen_x(0.0), 0.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_screen_x(10.0), 100.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_screen_y(-1.0), 0.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_screen_y(1.0), 200.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_data_x(t.to_screen_x(3.5)), 3.5, 1e-12);
  PLOT_CHECK_NEAR(t.to_data_y(t.to_screen_y(0.25)), 0.25, 1e-12);
}

PLOT_TEST(from_range_flipped_pixel_axis) {
  // px0 > px1 reverses the direction of the axis; the round trip must survive.
  const Transform t =
      Transform::from_range({0.0, 10.0}, {0.0, 10.0}, 100.0, 0.0, 200.0, 0.0, false, false);
  PLOT_CHECK_NEAR(t.to_screen_x(0.0), 100.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_screen_x(10.0), 0.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_screen_y(0.0), 200.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_screen_y(10.0), 0.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_data_x(t.to_screen_x(2.5)), 2.5, 1e-12);
  PLOT_CHECK_NEAR(t.to_data_y(t.to_screen_y(7.5)), 7.5, 1e-12);
}

PLOT_TEST(from_range_log_x) {
  const Transform t =
      Transform::from_range({1.0, 1000.0}, {0.0, 1.0}, 0.0, 300.0, 0.0, 100.0, true, false);
  PLOT_CHECK(t.log_x);
  PLOT_CHECK(!t.log_y);
  PLOT_CHECK_NEAR(t.to_screen_x(1.0), 0.0, 1e-12);
  PLOT_CHECK_NEAR(t.to_screen_x(1000.0), 300.0, 1e-12);
  // log10(31.6227766) == 1.5 lands exactly halfway along the axis.
  PLOT_CHECK_NEAR(t.to_screen_x(31.6227766), 150.0, 1e-6);
  PLOT_CHECK_NEAR(t.to_data_x(t.to_screen_x(31.6227766)), 31.6227766, 1e-9);
}

PLOT_TEST(from_range_degenerate_data_range) {
  // min == max: the range is widened, so the mapping stays finite and invertible.
  const Transform t =
      Transform::from_range({5.0, 5.0}, {2.0, 2.0}, 0.0, 100.0, 0.0, 200.0, false, false);
  PLOT_CHECK(std::isfinite(t.sx) && t.sx != 0.0);
  PLOT_CHECK(std::isfinite(t.sy) && t.sy != 0.0);
  PLOT_CHECK_NEAR(t.to_data_x(t.to_screen_x(5.0)), 5.0, 1e-9);
  PLOT_CHECK_NEAR(t.to_data_y(t.to_screen_y(2.0)), 2.0, 1e-9);
}

PLOT_TEST(from_range_collapsed_pixel_span) {
  // px0 == px1 previously gave sx == 0, so to_data_x returned NaN/inf.
  const Transform t =
      Transform::from_range({0.0, 10.0}, {0.0, 10.0}, 50.0, 50.0, 25.0, 25.0, false, false);
  PLOT_CHECK(std::isfinite(t.sx) && t.sx != 0.0);
  PLOT_CHECK(std::isfinite(t.sy) && t.sy != 0.0);
  PLOT_CHECK_NEAR(t.to_data_x(t.to_screen_x(4.0)), 4.0, 1e-9);
  PLOT_CHECK_NEAR(t.to_data_y(t.to_screen_y(7.0)), 7.0, 1e-9);
  PLOT_CHECK(std::isfinite(t.to_data_x(t.to_screen_x(0.0))));
  PLOT_CHECK(std::isfinite(t.to_data_y(t.to_screen_y(10.0))));
}

PLOT_TEST(log10_positive_clamps_non_positive) {
  PLOT_CHECK(std::isfinite(Transform::log10_positive(0.0)));
  PLOT_CHECK(std::isfinite(Transform::log10_positive(-5.0)));
  PLOT_CHECK_NEAR(Transform::log10_positive(1.0), 0.0, 1e-12);
}