/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

#include "ImGuiPlotTwoLines.hpp"

#include <imgui.h>
#include <imgui_internal.h>

namespace ImGui
{
    void PlotTwoLines(const char* label,
        float (*getter1)(void* data, int idx), void* data1, const char *tooltipPrefix1,
        float (*getter2)(void* data, int idx), void* data2, const char *tooltipPrefix2,
        int values_count, float scale_min, float scale_max, ImVec2 graph_size)
    {
        ImGuiContext& g = *ImGui::GetCurrentContext();
        ImGuiWindow* window = ImGui::GetCurrentWindow();
        if (window->SkipItems)
            return;

        const ImGuiStyle& style = g.Style;

        ImVec2 label_size = ImGui::CalcTextSize(label, NULL, true);
        if (graph_size.x == 0.0f)
            graph_size.x = ImGui::CalcItemWidth();
        if (graph_size.y == 0.0f)
            graph_size.y = label_size.y + (style.FramePadding.y * 2);

        ImRect frame_bb(window->DC.CursorPos, ImVec2(window->DC.CursorPos.x + graph_size.x, window->DC.CursorPos.y + graph_size.y));
        ImRect inner_bb(ImVec2(frame_bb.Min.x + style.FramePadding.x, frame_bb.Min.y + style.FramePadding.y), ImVec2(frame_bb.Max.x - style.FramePadding.x, frame_bb.Max.y - style.FramePadding.y));
        ImRect total_bb(frame_bb.Min, ImVec2(frame_bb.Max.x + (label_size.x > 0.0f ? (style.ItemInnerSpacing.x + label_size.x) : 0.0f), frame_bb.Max.y));

        ImGui::ItemSize(total_bb, style.FramePadding.y);
        if (!ImGui::ItemAdd(total_bb, 0))
            return;

        // Determine scale from inputs if not specified
        if (scale_min == FLT_MAX || scale_max == FLT_MAX)
        {
            float v1_min = FLT_MAX, v1_max = -FLT_MAX;
            for (int i = 0; i < values_count; i++)
            {
                float v = getter1(data1, i);
                if (v != v) // Ignore NaN values
                    continue;
                v1_min = ImMin(v1_min, v);
                v1_max = ImMax(v1_max, v);
            }
            float v2_min = FLT_MAX, v2_max = -FLT_MAX;
            for (int i = 0; i < values_count; i++)
            {
                float v = getter2(data2, i);
                if (v != v) // Ignore NaN values
                    continue;
                v2_min = ImMin(v2_min, v);
                v2_max = ImMax(v2_max, v);
            }
            if (scale_min == FLT_MAX) scale_min = ImMin(v1_min, v2_min);
            if (scale_max == FLT_MAX) scale_max = ImMax(v1_max, v2_max);
        }

        ImGui::RenderFrame(frame_bb.Min, frame_bb.Max, ImGui::GetColorU32(ImGuiCol_FrameBg), true, style.FrameRounding);
        int res_w = ImMin((int)graph_size.x, values_count); // Number of samples

        if (res_w <= 0)
            return;

        // Tooltip on hover
        int v_hovered = -1;
        if (ImGui::IsItemHovered())
        {
            const float t = ImClamp((g.IO.MousePos.x - inner_bb.Min.x) / (inner_bb.Max.x - inner_bb.Min.x), 0.0f, 0.9999f);
            const int v_idx = (int)(t * values_count);
            IM_ASSERT(v_idx >= 0 && v_idx < values_count);

            const float v0 = getter1(data1, v_idx);
            const float v1 = getter2(data2, v_idx);
            ImGui::SetTooltip("%d: (%s: %8.4g, %s: %8.4g)", v_idx, tooltipPrefix1, v0, tooltipPrefix2, v1);
            v_hovered = v_idx;
        }

        const float t_step = 1.0f / res_w;

        ImDrawList* draw_list = ImGui::GetWindowDrawList();
        draw_list->PushClipRect(inner_bb.Min, inner_bb.Max, true);

        ImColor col1 = ImColor(255, 100, 100);
        ImColor col2 = ImColor(100, 255, 100);

        // Plot first line
        for (int n = 0; n < res_w; n++)
        {
            const float t0 = t_step * (n + 0);
            const float t1 = t_step * (n + 1);
            const int v_idx0 = (int)(t0 * values_count);
            int v_idx1 = (int)(t1 * values_count);
            if(v_idx1 >= values_count)
                v_idx1 = values_count - 1;

            IM_ASSERT(v_idx0 >= 0 && v_idx0 < values_count);
            IM_ASSERT(v_idx1 >= 0 && v_idx1 < values_count);

            const float v0 = getter1(data1, v_idx0);
            const float v1 = getter1(data1, v_idx1);
            const float x0 = ImLerp(inner_bb.Min.x, inner_bb.Max.x, t0);
            const float x1 = ImLerp(inner_bb.Min.x, inner_bb.Max.x, t1);
            const float y0 = ImLerp(inner_bb.Max.y, inner_bb.Min.y, (v0 - scale_min) / (scale_max - scale_min));
            const float y1 = ImLerp(inner_bb.Max.y, inner_bb.Min.y, (v1 - scale_min) / (scale_max - scale_min));
            draw_list->AddLine(ImVec2(x0, y0), ImVec2(x1, y1), col1);
        }

        // Plot second line
        for (int n = 0; n < res_w; n++)
        {
            const float t0 = t_step * (n + 0);
            const float t1 = t_step * (n + 1);
            const int v_idx0 = (int)(t0 * values_count);
            int v_idx1 = (int)(t1 * values_count);
            if(v_idx1 >= values_count)
                v_idx1 = values_count - 1;

            IM_ASSERT(v_idx0 >= 0 && v_idx0 < values_count);
            IM_ASSERT(v_idx1 >= 0 && v_idx1 < values_count);

            const float v0 = getter2(data2, v_idx0);
            const float v1 = getter2(data2, v_idx1);
            const float x0 = ImLerp(inner_bb.Min.x, inner_bb.Max.x, t0);
            const float x1 = ImLerp(inner_bb.Min.x, inner_bb.Max.x, t1);
            const float y0 = ImLerp(inner_bb.Max.y, inner_bb.Min.y, (v0 - scale_min) / (scale_max - scale_min));
            const float y1 = ImLerp(inner_bb.Max.y, inner_bb.Min.y, (v1 - scale_min) / (scale_max - scale_min));
            draw_list->AddLine(ImVec2(x0, y0), ImVec2(x1, y1), col2);
        }

        draw_list->PopClipRect();

        if (label_size.x > 0.0f)
            ImGui::RenderText(ImVec2(frame_bb.Max.x + style.ItemInnerSpacing.x, inner_bb.Min.y), label);
    }
}