/*******************************************************************************************
*
*   CurveEdit v1.0 - A cubic Hermite editor for making animation curves
*
*   MODULE USAGE:
*       #define GUI_CURVE_EDITOR_IMPLEMENTATION
*       #include "gui_curve_edit.h"
*
*       INIT: GuiCurveEditState state = InitCurveEdit();
*       EVALUATE: float y = EvalGuiCurve(&state, t); // 0 <= t <= 1
*       DRAW: BeginScissorMode(bounds.x,bounds.y,bounds.width,bounds.height);
*               GuiCurveEdit(&state, bounds, pointSize);
*             EndScissorMode();
*
*   NOTE: See 'Module Structures Declaration' section for more informations.
*
*   NOTE: This module uses functions of the stdlib:
*       - qsort
*
*   NOTE: Built-in interactions:
*       - Left click to move/add point or move tangents
*       - While moving a tangent, hold (left/right) SHIFT to disable tangent symetry
*       - Right click to remove a point
*
*
*   LICENSE: zlib/libpng
*
*   Copyright (c) 2023 Pierre Jaffuer (@smallcluster)
*
*   This software is provided "as-is", without any express or implied warranty. In no event
*   will the authors be held liable for any damages arising from the use of this software.
*
*   Permission is granted to anyone to use this software for any purpose, including commercial
*   applications, and to alter it and redistribute it freely, subject to the following restrictions:
*
*     1. The origin of this software must not be misrepresented; you must not claim that you
*     wrote the original software. If you use this software in a product, an acknowledgment
*     in the product documentation would be appreciated but is not required.
*
*     2. Altered source versions must be plainly marked as such, and must not be misrepresented
*     as being the original software.
*
*     3. This notice may not be removed or altered from any source distribution.
*
**********************************************************************************************/

#include "raylib.h"

#ifndef GUI_CURVE_EDITOR_H
#define GUI_CURVE_EDITOR_H


#ifndef GUI_CURVE_EDITOR_MAX_POINTS
    #define GUI_CURVE_EDITOR_MAX_POINTS 30
#endif

//----------------------------------------------------------------------------------
// Module Structures Declaration
//----------------------------------------------------------------------------------

typedef struct {
    Vector2 position;   // In normalized space [0.0f, 1.0f]
    Vector2 tangents;   // The derivatives (left/right) of the 1D curve

    // Let the curve editor calculate tangents to linearize part of the curve
    bool leftLinear;
    bool rightLinear;
} GuiCurveEditorPoint;

typedef struct {
    float start;        // Value at y = 0
    float end;          // Value at y = 1

    // Always valid (unless you manualy change state's point array). Make sure to set it to -1 before init
    int selectedIndex;

    // Unsorted array with at least one point (constant curve)
    GuiCurveEditorPoint points[GUI_CURVE_EDITOR_MAX_POINTS];
    int numPoints;

    // Private variables
    bool editLeftTangent;
    bool editRightTangent;
    Vector2 mouseOffset;
} GuiCurveEditorState;


#ifdef __cplusplus
extern "C" {            // Prevents name mangling of functions
#endif

//----------------------------------------------------------------------------------
// Module Functions Declaration
//----------------------------------------------------------------------------------
GuiCurveEditorState InitGuiCurveEditor();     // Initialize curve editor state
void GuiCurveEditor(GuiCurveEditorState *state, Rectangle bounds);  // Draw and update curve control

// 1D Interpolation
// Returns the y value (in [start, end]) of the curve at x = t
// t must be normalized [0.f, 1.f]
float GuiCurveEval(GuiCurveEditorState *state, float t);

#ifdef __cplusplus
}
#endif

#endif // GUI_CURVE_EDITOR_H

/***********************************************************************************
*
*   GUI_CURVE_EDITOR IMPLEMENTATION
*
************************************************************************************/
#if defined(GUI_CURVE_EDITOR_IMPLEMENTATION)

#include "../../src/raygui.h" // Change this to fit your project

#include "stdlib.h" // Required for qsort

//----------------------------------------------------------------------------------
// Module Functions Definition
//----------------------------------------------------------------------------------
GuiCurveEditorState InitGuiCurveEditor()
{
    GuiCurveEditorState state = { 0 };

    state.start = 0;
    state.end = 1;
    state.selectedIndex = 0;
    state.editLeftTangent = false;
    state.editRightTangent = false;
    state.mouseOffset = (Vector2){ 0.0f, 0.0f };

    // At least one point (AVG by default)
    state.numPoints = 1;
    state.points[0].position = (Vector2){ 0.5f, 0.5f };
    state.points[0].tangents = (Vector2){ 0.0f, 0.0f };
    state.points[0].leftLinear = false;
    state.points[0].rightLinear = false;

    return state;
}

static int CompareGuiCurveEditPointPtr(const void *a, const void *b)
{
    float fa = (*(GuiCurveEditorPoint**)a)->position.x;
    float fb = (*(GuiCurveEditorPoint**)b)->position.x;

    return ((fa > fb) - (fa < fb));
}

float GuiCurveEval(GuiCurveEditorState *state, float t)
{
    // Sort points
    GuiCurveEditorPoint* sortedPoints[GUI_CURVE_EDITOR_MAX_POINTS];

    for (int i=0; i < state->numPoints; i++) sortedPoints[i] = &state->points[i];

    qsort(sortedPoints, state->numPoints, sizeof(GuiCurveEditorPoint*), CompareGuiCurveEditPointPtr);

    if (state->numPoints == 0) return state->start;

    // Constants part on edges
    if (t <= sortedPoints[0]->position.x) return state->start + (state->end-state->start)*sortedPoints[0]->position.y;
    if (t >= sortedPoints[state->numPoints-1]->position.x) return state->start + (state->end-state->start)*sortedPoints[state->numPoints-1]->position.y;

    // Find curve portion
    for (int i=0; i < state->numPoints-1; i++)
    {
        const GuiCurveEditorPoint *p1 = sortedPoints[i];
        const GuiCurveEditorPoint *p2 = sortedPoints[i+1];

        // Skip this range
        if (!((t >= p1->position.x) && (t < p2->position.x)) || (p1->position.x == p2->position.x)) continue;

        float scale = (p2->position.x-p1->position.x);
        float T = (t-p1->position.x)/scale;
        float startTangent = scale*p1->tangents.y;
        float endTangent = scale*p2->tangents.x;
        float T2 = T*T;
        float T3 = T*T*T;

        return (state->start + (state->end-state->start)*((2*T3 - 3*T2 + 1)*p1->position.y + (T3 - 2*T2 + T)*startTangent + (3*T2 - 2*T3)*p2->position.y + (T3 - T2)*endTangent));
    }

    return state->start;
}

void GuiCurveEditor(GuiCurveEditorState *state, Rectangle bounds)
{
    // CONST
    //----------------------------------------------------------------------------------
    const float pointSize = 10.0f;
    const float fontSize = GuiGetStyle(DEFAULT, TEXT_SIZE);
    const float handleLength = pointSize*2.5f;
    const float handleSize = pointSize/1.5f;

    const Rectangle innerBounds = (Rectangle){ bounds.x + fontSize, bounds.y + fontSize, bounds.width - 2*fontSize, bounds.height - 2*fontSize };
    const Vector2 mouse = GetMousePosition();
    const Vector2 mouseLocal = (Vector2){ (mouse.x - innerBounds.x)/innerBounds.width, (innerBounds.y + innerBounds.height-mouse.y)/innerBounds.height};
    //----------------------------------------------------------------------------------

    // UPDATE STATE
    //----------------------------------------------------------------------------------
    // Find first point under mouse (-1 if not found)
    int hoveredPointIndex = -1;
    for (int i = 0; i < state->numPoints; i++)
    {
        const GuiCurveEditorPoint *p = &state->points[i];
        const Vector2 screenPos = (Vector2){ p->position.x*innerBounds.width + innerBounds.x, innerBounds.y + innerBounds.height-p->position.y*innerBounds.height };
        const Rectangle pointRect = (Rectangle){ screenPos.x - pointSize/2.0f, screenPos.y - pointSize/2.0f, pointSize, pointSize };

        if (CheckCollisionPointRec(mouse, pointRect))
        {
            hoveredPointIndex = i;
            break;
        }
    }

    // Unselect tangents
    if (IsMouseButtonReleased(MOUSE_BUTTON_LEFT))
    {
        state->editLeftTangent = false;
        state->editRightTangent = false;
    }

    // Select a tangent if possible
    if (IsMouseButtonPressed(MOUSE_BUTTON_LEFT) && (state->selectedIndex != -1) && CheckCollisionPointRec(mouse, bounds))
    {
        const GuiCurveEditorPoint* p = &state->points[state->selectedIndex];
        const Vector2 screenPos = (Vector2){ p->position.x*innerBounds.width+innerBounds.x, innerBounds.y+innerBounds.height-p->position.y*innerBounds.height };

        // Left control
        Vector2 target = (Vector2){ (p->position.x-1)*innerBounds.width + innerBounds.x, innerBounds.y + innerBounds.height - (p->position.y-p->tangents.x)*innerBounds.height };
        Vector2 dir = (Vector2){ target.x-screenPos.x, target.y-screenPos.y };
        float d = sqrt(dir.x*dir.x + dir.y*dir.y);
        Vector2 control = (Vector2){ screenPos.x + dir.x/d*handleLength, screenPos.y + dir.y/d*handleLength };
        Rectangle controlRect = (Rectangle){ control.x - handleSize/2.0f, control.y - handleSize/2.0f, handleSize, handleSize };

        // Edit left tangent
        if (CheckCollisionPointRec(mouse, controlRect)) state->editLeftTangent = true;

        // Right control
        target = (Vector2){ (p->position.x + 1)*innerBounds.width + innerBounds.x, innerBounds.y + innerBounds.height - (p->position.y + p->tangents.y)*innerBounds.height };
        dir = (Vector2){ target.x-screenPos.x, target.y-screenPos.y };
        d = sqrt(dir.x*dir.x + dir.y*dir.y);
        control = (Vector2){ screenPos.x + dir.x/d*handleLength, screenPos.y + dir.y/d*handleLength };
        controlRect = (Rectangle){ control.x - handleSize/2.0f, control.y - handleSize/2.0f, handleSize, handleSize };

        // Edit right tangent
        if (CheckCollisionPointRec(mouse, controlRect)) state->editRightTangent = true;
    }

    // Move tangents
    if (IsMouseButtonDown(MOUSE_BUTTON_LEFT) && state->editRightTangent)
    {
        // editRightTangent == true implies selectedIndex != -1
        GuiCurveEditorPoint *p = &state->points[state->selectedIndex];
        const Vector2 dir = (Vector2){ mouseLocal.x - p->position.x, mouseLocal.y - p->position.y};

        // Calculate right tangent slope
        p->tangents.y = (dir.x < 0.001f)? dir.y/0.001f : dir.y/dir.x;
        p->rightLinear = false; // Stop right linearization update

        // Tangents are symetric by default unless SHIFT is pressed
        if (!(IsKeyDown(KEY_LEFT_SHIFT) || IsKeyDown(KEY_RIGHT_SHIFT)))
        {
            p->tangents.x = p->tangents.y;
            p->leftLinear = false; // Stop left linearization update
        }

    }
    else if (IsMouseButtonDown(MOUSE_BUTTON_LEFT) && state->editLeftTangent)
    {
        // editLeftTangent == true implies selectedIndex != -1
        GuiCurveEditorPoint *p = &state->points[state->selectedIndex];
        const Vector2 dir = (Vector2){ mouseLocal.x - p->position.x, mouseLocal.y - p->position.y };

        // Calculate left tangent slope
        p->tangents.x = (dir.x > -0.001f)? dir.y/(-0.001f) : dir.y/dir.x;
        p->leftLinear = false; // Stop left linearization update

        // Tangents are symetric by default unless SHIFT is pressed
        if (!(IsKeyDown(KEY_LEFT_SHIFT) || IsKeyDown(KEY_RIGHT_SHIFT)))
        {
            p->tangents.y = p->tangents.x;
            p->rightLinear = false; // Stop right linearization update
        }
    }
    // Select a point
    else if (IsMouseButtonPressed(MOUSE_BUTTON_LEFT) && (hoveredPointIndex != -1) && CheckCollisionPointRec(mouse, bounds))
    {
        state->selectedIndex = hoveredPointIndex;
        const GuiCurveEditorPoint *p = &state->points[state->selectedIndex];
        state->mouseOffset = (Vector2){ p->position.x - mouseLocal.x, p->position.y - mouseLocal.y };
    }
    // Remove a point (check against bounds)
    else if (IsMouseButtonPressed(MOUSE_BUTTON_RIGHT) && (hoveredPointIndex != -1) && CheckCollisionPointRec(mouse, bounds) && (state->numPoints > 1))
    {
        // Deselect everything
        state->selectedIndex = 0; // select first point by default
        state->editLeftTangent = false;
        state->editRightTangent = false;

        // Remove point
        state->numPoints -= 1;
        for (int i = hoveredPointIndex; i < state->numPoints; i++) state->points[i] = state->points[i+1];
    }
    // Add a point (check against innerBounds)
    else if (IsMouseButtonPressed(MOUSE_BUTTON_LEFT) && CheckCollisionPointRec(mouse, innerBounds) && (state->numPoints < GUI_CURVE_EDITOR_MAX_POINTS))
    {
        state->editLeftTangent = false;
        state->editRightTangent = false;

        // Create new point
        GuiCurveEditorPoint p;
        p.tangents = (Vector2){ 0.0f, 0.0f };
        p.position = mouseLocal;
        p.leftLinear = false;
        p.rightLinear = false;

        // Append point
        state->points[state->numPoints] = p;
        state->selectedIndex = state->numPoints; // select new point
        state->numPoints += 1;

        // Point is add on mouse pos
        state->mouseOffset = (Vector2){ 0, 0 };
    }
    // Move selected point
    else if ((state->selectedIndex != -1) && IsMouseButtonDown(MOUSE_BUTTON_LEFT) && CheckCollisionPointRec(mouse, bounds))
    {
        GuiCurveEditorPoint *p = &state->points[state->selectedIndex];

        // use mouse offset on click to prevent point teleporting to mouse
        const Vector2 newLocalPos = (Vector2){ mouseLocal.x + state->mouseOffset.x, mouseLocal.y + state->mouseOffset.y };

        // Clamp to innerbounds
        p->position.x = (newLocalPos.x < 0)? 0 : ((newLocalPos.x > 1)? 1 : newLocalPos.x);
        p->position.y = (newLocalPos.y < 0)? 0 : ((newLocalPos.y > 1)? 1 : newLocalPos.y);
    }

    // Sort points
    GuiCurveEditorPoint *sortedPoints[GUI_CURVE_EDITOR_MAX_POINTS] = { 0 };
    for (int i = 0; i < state->numPoints; i++) sortedPoints[i] = &state->points[i];
    qsort(sortedPoints, state->numPoints, sizeof(GuiCurveEditorPoint*), CompareGuiCurveEditPointPtr);

    // Update linear tangents
    for (int i = 0; i < state->numPoints; i++)
    {
        GuiCurveEditorPoint *p = sortedPoints[i];

        // Left tangent
        if ((i > 0) && p->leftLinear)
        {
            const GuiCurveEditorPoint *p2 = sortedPoints[i - 1];
            Vector2 dir = (Vector2){ p2->position.x - p->position.x, p2->position.y - p->position.y };
            p->tangents.x = (dir.x == 0)? 0 : dir.y/dir.x;
        }

        // Right tangent
        if ((i < state->numPoints - 1) && p->rightLinear)
        {
            const GuiCurveEditorPoint *p2 = sortedPoints[i + 1];
            Vector2 dir = (Vector2){ p2->position.x - p->position.x, p2->position.y - p->position.y };
            p->tangents.y = (dir.x == 0)? 0 : dir.y/dir.x;
        }
    }
    //----------------------------------------------------------------------------------

    // DRAWING
    //----------------------------------------------------------------------------------
    DrawRectangle(bounds.x, bounds.y, bounds.width, bounds.height, GetColor(GuiGetStyle(DEFAULT, BACKGROUND_COLOR)));

    // Draw grid
    // H lines
    const Color lineColor = GetColor(GuiGetStyle(DEFAULT, BORDER_COLOR_NORMAL));
    DrawLine(bounds.x, innerBounds.y, bounds.x+bounds.width, innerBounds.y, lineColor); // end
    DrawLine(bounds.x, innerBounds.y+innerBounds.height/2, bounds.x+bounds.width, innerBounds.y+innerBounds.height/2, lineColor); // avg
    DrawLine(bounds.x, innerBounds.y+innerBounds.height, bounds.x+bounds.width, innerBounds.y+innerBounds.height, lineColor); // start

    // V lines
    DrawLine(innerBounds.x, bounds.y, innerBounds.x, bounds.y+bounds.height, lineColor); // 0
    DrawLine(innerBounds.x + innerBounds.width/4, bounds.y, innerBounds.x + innerBounds.width/4, bounds.y + bounds.height, lineColor); // 0.25
    DrawLine(innerBounds.x + innerBounds.width/2, bounds.y, innerBounds.x + innerBounds.width/2, bounds.y + bounds.height, lineColor); // 0.5
    DrawLine(innerBounds.x + 3*innerBounds.width/4, bounds.y, innerBounds.x + 3*innerBounds.width/4, bounds.y + bounds.height, lineColor); // 0.75
    DrawLine(innerBounds.x + innerBounds.width, bounds.y, innerBounds.x + innerBounds.width, bounds.y + bounds.height, lineColor); // 1

    Font font = GuiGetFont();
    // V labels
    DrawTextEx(font, "0", (Vector2){ innerBounds.x, bounds.y + bounds.height-fontSize}, fontSize, GuiGetStyle(DEFAULT, TEXT_SPACING), lineColor);
    DrawTextEx(font, "0.25", (Vector2){ innerBounds.x + innerBounds.width/4.0f, bounds.y + bounds.height - fontSize}, fontSize, GuiGetStyle(DEFAULT, TEXT_SPACING), lineColor);
    DrawTextEx(font, "0.5", (Vector2){ innerBounds.x + innerBounds.width/2.0f, bounds.y + bounds.height - fontSize}, fontSize, GuiGetStyle(DEFAULT, TEXT_SPACING), lineColor);
    DrawTextEx(font, "0.75", (Vector2){ innerBounds.x + 3.0f*innerBounds.width/4.0f, bounds.y + bounds.height-fontSize}, fontSize, GuiGetStyle(DEFAULT, TEXT_SPACING), lineColor);
    DrawTextEx(font, "1", (Vector2){ innerBounds.x + innerBounds.width, bounds.y+bounds.height - fontSize}, fontSize, GuiGetStyle(DEFAULT, TEXT_SPACING), lineColor);

    // H labels
    DrawTextEx(font, TextFormat("%.2f", state->start), (Vector2){ innerBounds.x, innerBounds.y - fontSize+innerBounds.height }, fontSize, GuiGetStyle(DEFAULT, TEXT_SPACING), lineColor);
    DrawTextEx(font, TextFormat("%.2f", state->start + (state->end-state->start)/2.f), (Vector2){ innerBounds.x, innerBounds.y - fontSize + innerBounds.height/2.0f }, fontSize, GuiGetStyle(DEFAULT, TEXT_SPACING), lineColor);
    DrawTextEx(font, TextFormat("%.2f", state->end), (Vector2){ innerBounds.x, innerBounds.y }, fontSize, GuiGetStyle(DEFAULT, TEXT_SPACING), lineColor);

    // Draw contours
    if (CheckCollisionPointRec(mouse, bounds)) DrawRectangleLines(bounds.x, bounds.y, bounds.width, bounds.height, GetColor(GuiGetStyle(DEFAULT, BORDER_COLOR_FOCUSED)));
    else DrawRectangleLines(bounds.x, bounds.y, bounds.width, bounds.height, GetColor(GuiGetStyle(DEFAULT, BORDER_COLOR_NORMAL)));

    // Draw points
    for (int i = 0; i < state->numPoints; i++)
    {
        const GuiCurveEditorPoint *p = sortedPoints[i];

        const Vector2 screenPos = (Vector2){ p->position.x*innerBounds.width + innerBounds.x, innerBounds.y + innerBounds.height - p->position.y*innerBounds.height };
        const Rectangle pointRect = (Rectangle){ screenPos.x - pointSize/2.0f, screenPos.y - pointSize/2.0f, pointSize, pointSize };

        Color pointColor = { 0 };
        Color pointBorderColor = { 0 };

        // Draw point
        if (&state->points[state->selectedIndex] == p)
        {
            // Draw left handle
            if (i > 0)
            {
                const Vector2 target = (Vector2){ (p->position.x - 1)*innerBounds.width + innerBounds.x, innerBounds.y + innerBounds.height - (p->position.y - p->tangents.x)*innerBounds.height };
                const Vector2 dir = (Vector2){ target.x - screenPos.x, target.y - screenPos.y };
                const float d = sqrt(dir.x*dir.x + dir.y*dir.y);
                const Vector2 control = (Vector2){ screenPos.x + dir.x/d*handleLength, screenPos.y + dir.y/d*handleLength };
                const Rectangle controlRect = (Rectangle){ control.x - handleSize/2.0f, control.y - handleSize/2.0f, handleSize, handleSize };

                Color controlColor = { 0 };

                if (state->editLeftTangent)
                {
                    controlColor = GetColor(GuiGetStyle(DEFAULT, BASE_COLOR_PRESSED));
                }
                else if (CheckCollisionPointRec(mouse, controlRect))
                {
                    controlColor = GetColor(GuiGetStyle(DEFAULT, BASE_COLOR_FOCUSED));
                }
                else
                {
                    controlColor = GetColor(GuiGetStyle(BUTTON, BASE_COLOR_NORMAL));
                }

                DrawLine(screenPos.x,screenPos.y, control.x, control.y, controlColor);
                DrawRectangle(controlRect.x, controlRect.y, controlRect.width, controlRect.height, controlColor);
                DrawRectangleLines(controlRect.x, controlRect.y, controlRect.width, controlRect.height, controlColor);
            }

            // Draw right handle
            if (i < state->numPoints - 1)
            {
                const Vector2 target = (Vector2){ (p->position.x + 1)*innerBounds.width + innerBounds.x, innerBounds.y + innerBounds.height - (p->position.y + p->tangents.y)*innerBounds.height };
                const Vector2 dir = (Vector2){ target.x - screenPos.x, target.y - screenPos.y };
                const float d = sqrt(dir.x*dir.x + dir.y*dir.y);
                const Vector2 control = (Vector2){ screenPos.x + dir.x/d*handleLength, screenPos.y + dir.y/d*handleLength };
                const Rectangle controlRect = (Rectangle){ control.x - handleSize/2.0f, control.y - handleSize/2.0f, handleSize, handleSize };

                Color controlColor = { 0 };

                if (state->editRightTangent)
                {
                    controlColor = GetColor(GuiGetStyle(DEFAULT, BASE_COLOR_PRESSED));
                }
                else if (CheckCollisionPointRec(mouse, controlRect))
                {
                    controlColor = GetColor(GuiGetStyle(DEFAULT, BASE_COLOR_FOCUSED));
                }
                else
                {
                    controlColor = GetColor(GuiGetStyle(BUTTON, BASE_COLOR_NORMAL));
                }

                DrawLine(screenPos.x,screenPos.y, control.x, control.y, controlColor);
                DrawRectangle(controlRect.x, controlRect.y, controlRect.width, controlRect.height, controlColor);
                DrawRectangleLines(controlRect.x, controlRect.y, controlRect.width, controlRect.height, controlColor);
            }

            pointColor = GetColor(GuiGetStyle(DEFAULT, BASE_COLOR_PRESSED));
            pointBorderColor = GetColor(GuiGetStyle(DEFAULT, BORDER_COLOR_NORMAL));

        }
        else if (&state->points[hoveredPointIndex] == p)
        {
            pointColor = GetColor(GuiGetStyle(DEFAULT, BASE_COLOR_FOCUSED));
            pointBorderColor = GetColor(GuiGetStyle(DEFAULT, BORDER_COLOR_NORMAL));
        }
        else
        {
            pointColor = GetColor(GuiGetStyle(BUTTON, BASE_COLOR_NORMAL));
            pointBorderColor = GetColor(GuiGetStyle(BUTTON, BORDER_COLOR_NORMAL));
        }

        DrawRectangle(pointRect.x, pointRect.y, pointRect.width, pointRect.height, pointColor);
        DrawRectangleLines(pointRect.x, pointRect.y, pointRect.width, pointRect.height, pointBorderColor);
    }

    // Draw curve
    Color curveColor = GetColor(GuiGetStyle(LABEL,  TEXT_COLOR_FOCUSED));

    if (state->numPoints == 1)
    {
        const GuiCurveEditorPoint *p = sortedPoints[0];
        const Vector2 screenPos = (Vector2){ p->position.x*innerBounds.width + innerBounds.x, innerBounds.y + innerBounds.height - p->position.y*innerBounds.height };
        DrawLine(innerBounds.x, screenPos.y, innerBounds.x+innerBounds.width, screenPos.y, curveColor);
    }
    else
    {
        for (int i = 0; i < state->numPoints - 1; i++)
        {
            const GuiCurveEditorPoint *p1 = sortedPoints[i];
            const GuiCurveEditorPoint *p2 = sortedPoints[i + 1];
            const Vector2 screenPos1 = (Vector2){ p1->position.x*innerBounds.width + innerBounds.x, innerBounds.y + innerBounds.height - p1->position.y*innerBounds.height };
            const Vector2 screenPos2 = (Vector2){ p2->position.x*innerBounds.width + innerBounds.x, innerBounds.y + innerBounds.height - p2->position.y*innerBounds.height };

            // Constant on edge
            if ((screenPos1.x > innerBounds.x) && (i == 0))
            {
                DrawLine(innerBounds.x, screenPos1.y, screenPos1.x, screenPos1.y, curveColor);
            }
            if ((screenPos2.x < innerBounds.x + innerBounds.width) && (i == (state->numPoints - 2)))
            {
                DrawLine(screenPos2.x, screenPos2.y, innerBounds.x+innerBounds.width, screenPos2.y, curveColor);
            }

            // Draw cubic Hermite curve
            const float scale = (p2->position.x - p1->position.x)/3.0f;
            const Vector2 offset1 = (Vector2){ scale, scale*p1->tangents.y };
            // negative endTangent => top part => need to invert value to calculate offset
            const Vector2 offset2 = (Vector2){ -scale, -scale*p2->tangents.x };

            const Vector2 c1 = (Vector2){ p1->position.x + offset1.x, p1->position.y + offset1.y };
            const Vector2 c2 = (Vector2){ p2->position.x + offset2.x, p2->position.y + offset2.y };

            const Vector2 screenC1 = (Vector2){ c1.x*innerBounds.width + innerBounds.x, innerBounds.y + innerBounds.height - c1.y*innerBounds.height };
            const Vector2 screenC2 = (Vector2){ c2.x*innerBounds.width + innerBounds.x, innerBounds.y + innerBounds.height - c2.y*innerBounds.height };

            DrawSplineSegmentBezierCubic(screenPos1, screenC1, screenC2, screenPos2, 1, curveColor);
        }
    }
}

#endif // GUI_CURVE_EDITOR_IMPLEMENTATION

