//
// File: foldhaus_animation.h
// Author: Peter Slattery
// Creation Date: 2020-01-01
//
#ifndef FOLDHAUS_ANIMATION

#define ANIMATION_PROC(name) void name(led_buffer* Leds, assembly Assembly, r32 Time, gs_memory_arena* Transient, u8* UserData)
typedef ANIMATION_PROC(animation_proc);

struct frame_range
{
    s32 Min;
    s32 Max;
};

struct animation_pattern_handle
{
    s32 IndexPlusOne;
};

// NOTE(pjs): An animation block is a time range paired with an
// animation_pattern (see below). While a timeline's current time
// is within the range of a block, that particular block's animation
// will run
struct animation_block
{
    frame_range Range;
    animation_pattern_handle AnimationProcHandle;
    u32 Layer;
};

struct animation_block_array
{
    u32* Generations;
    animation_block* Values;
    u32 Count;
    u32 CountMax;
};

enum blend_mode
{
    BlendMode_Overwrite,
    BlendMode_Add,
    BlendMode_Multiply,
    BlendMode_Count,
};

// TODO(pjs): This really doesn't belong here
global gs_const_string BlendModeStrings[] = {
    ConstString("Overwrite"),
    ConstString("Add"),
    ConstString("Multiply"),
    ConstString("Count"),
};

struct anim_layer
{
    gs_string Name;
    blend_mode BlendMode;
};

struct anim_layer_array
{
    anim_layer* Values;
    u32 Count;
    u32 CountMax;
};

// NOTE(pjs): An animation is a stack of layers, each of which
// is a timeline of animation blocks.
struct animation
{
    gs_string Name;
    
    anim_layer_array Layers;
    // TODO(pjs): Pretty sure Blocks_ should be obsolete and
    // Layers should contain their own blocks
    animation_block_array Blocks_;
    
    frame_range PlayableRange;
    
    // The information / path to the file where this animation is to be saved / where it is loaded from
    gs_file_info FileInfo;
};

struct animation_handle
{
    s32 Index;
};

internal bool IsValid (animation_handle H) { return H.Index >= 0; }
internal void Clear (animation_handle* H) { H->Index = -1; }
internal bool AnimHandlesAreEqual (animation_handle A, animation_handle B)
{
    return A.Index == B.Index;
}

struct animation_array
{
    animation* Values;
    u32 Count;
    u32 CountMax;
};

struct animation_layer_frame
{
    animation_block Hot;
    bool HasHot;
    
    animation_block NextHot;
    bool HasNextHot;
    
    r32 NextHotOpacity;
    
    blend_mode BlendMode;
};

// NOTE(pjs): This is an evaluated frame - across all layers in an
// animation, these are the blocks that need to be run
struct animation_frame
{
    animation_layer_frame* Layers;
    u32 LayersCount;
};

enum animation_repeat_mode
{
    AnimationRepeat_Single,
    AnimationRepeat_Loop,
    AnimationRepeat_Invalid,
};

global gs_const_string AnimationRepeatModeStrings[] = {
    ConstString("Repeat Single"),
    ConstString("Loop"),
    ConstString("Invalid"),
};

struct animation_fade_group
{
    animation_handle From;
    animation_handle To;
    r32 FadeElapsed;
    r32 FadeDuration;
};

#define ANIMATION_SYSTEM_LAYERS_MAX 128
#define ANIMATION_SYSTEM_BLOCKS_MAX 128
struct animation_system
{
    gs_memory_arena* Storage;
    animation_array Animations;
    
    animation_repeat_mode RepeatMode;
    
    // NOTE(Peter): The frame currently being displayed/processed. you
    // can see which frame you're on by looking at the time slider on the timeline
    // panel
    animation_handle ActiveAnimationHandle_;
    animation_fade_group ActiveFadeGroup;
    
    s32 CurrentFrame;
    s32 LastUpdatedFrame;
    r32 SecondsPerFrame;
    b32 TimelineShouldAdvance;
    
};

// NOTE(pjs): A Pattern is a named procedure which can be used as
// an element of an animation. Patterns are sequenced on a timeline
// and blended via layers to create an animation
struct animation_pattern
{
    char* Name;
    s32 NameLength;
    animation_proc* Proc;
};

struct animation_pattern_array
{
    animation_pattern* Values;
    u32 Count;
    u32 CountMax;
};

// Serialization

enum animation_field
{
    AnimField_FileIdent,
    AnimField_AnimName,
    AnimField_LayersCount,
    AnimField_BlocksCount,
    
    AnimField_PlayableRange,
    AnimField_PlayableRangeMin,
    AnimField_PlayableRangeMax,
    
    AnimField_LayersArray,
    AnimField_Layer,
    AnimField_LayerName,
    AnimField_LayerBlendMode,
    
    AnimField_BlocksArray,
    AnimField_Block,
    AnimField_BlockFrameRange,
    AnimField_BlockFrameRangeMin,
    AnimField_BlockFrameRangeMax,
    AnimField_BlockLayerIndex,
    AnimField_BlockAnimName,
    
    AnimField_Count,
};

global gs_const_string AnimationFieldStrings[] = {
    ConstString("lumenarium_animation_file"), // AnimField_FileIdent
    ConstString("animation_name"),// AnimField_AnimName
    ConstString("layers_count"),// AnimField_LayersCount
    ConstString("blocks_count"),// AnimField_BlocksCount
    
    ConstString("playable_range"),// AnimField_PlayableRange
    ConstString("min"),// AnimField_PlayableRangeMin
    ConstString("max"),// AnimField_PlayableRangeMax
    
    ConstString("layers"),// AnimField_LayersArray
    ConstString("layer"),// AnimField_Layer
    ConstString("name"),// AnimField_LayerName
    ConstString("blend"),// AnimField_LayerBlendMode
    
    ConstString("blocks"),// AnimField_BlocksArray
    ConstString("block"),// AnimField_Block
    ConstString("frame_range"),// AnimField_BlockFrameRange
    ConstString("min"),// AnimField_BlockFrameRangeMin
    ConstString("max"),// AnimField_BlockFrameRangeMax
    ConstString("layer_index"),// AnimField_BlockLayerIndex
    ConstString("animation_name"),// AnimField_BlockAnimName
};


//////////////////////////
//
// Patterns List

internal animation_pattern_array
Patterns_Create(gs_memory_arena* Arena, s32 CountMax)
{
    animation_pattern_array Result = {0};
    Result.CountMax = CountMax;
    Result.Values = PushArray(Arena, animation_pattern, Result.CountMax);
    return Result;
}

#define Patterns_PushPattern(array, proc) Patterns_PushPattern_((array), (proc), Stringify(proc), sizeof(Stringify(proc)) - 1)
internal void
Patterns_PushPattern_(animation_pattern_array* Array, animation_proc* Proc, char* Name, u32 NameLength)
{
    Assert(Array->Count < Array->CountMax);
    
    animation_pattern Pattern = {0};
    Pattern.Name = Name;
    Pattern.NameLength = NameLength;
    Pattern.Proc = Proc;
    
    Array->Values[Array->Count++] = Pattern;
}

internal animation_pattern_handle
Patterns_IndexToHandle(s32 Index)
{
    animation_pattern_handle Result = {};
    Result.IndexPlusOne = Index + 1;
    return Result;
}

internal animation_pattern
Patterns_GetPattern(animation_pattern_array Patterns, animation_pattern_handle Handle)
{
    animation_pattern Result = {0};
    if (Handle.IndexPlusOne > 0)
    {
        u32 Index = Handle.IndexPlusOne - 1;
        Assert(Index < Patterns.Count);
        Result = Patterns.Values[Index];
    }
    return Result;
}

//////////////////////////
//
// Anim Block Array

internal animation_block_array
AnimBlockArray_Create(gs_memory_arena* Storage, u32 CountMax)
{
    animation_block_array Result = {0};
    Result.CountMax = CountMax;
    Result.Values = PushArray(Storage, animation_block, Result.CountMax);
    Result.Generations = PushArray(Storage, u32, Result.CountMax);
    return Result;
}

internal handle
AnimBlockArray_Push(animation_block_array* Array, animation_block Value)
{
    Assert(Array->Count < Array->CountMax);
    handle Result = {0};
    Result.Index = Array->Count++;
    // NOTE(pjs): pre-increment so that generation 0 is always invalid
    Result.Generation = ++Array->Generations[Result.Index];
    
    Array->Values[Result.Index] = Value;
    
    return Result;
}

internal void
AnimBlockArray_Remove(animation_block_array* Array, handle Handle)
{
    Assert(Handle.Index < Array->Count);
    Assert(Handle_IsValid(Handle));
    Array->Generations[Handle.Index]++;
}

internal void
AnimBlockArray_RemoveAt(animation_block_array* Array, u32 Index)
{
    Assert(Index < Array->Count);
    
    handle Handle = {};
    Handle.Index = Index;
    Handle.Generation = Array->Generations[Index];
    AnimBlockArray_Remove(Array, Handle);
}

//////////////////////////
//
// Anim Layers Array

internal anim_layer_array
AnimLayerArray_Create(gs_memory_arena* Storage, u32 CountMax)
{
    anim_layer_array Result = {0};
    Result.CountMax = CountMax;
    Result.Values = PushArray(Storage, anim_layer, Result.CountMax);
    return Result;
}

internal u32
AnimLayerArray_Push(anim_layer_array* Array, anim_layer Value)
{
    Assert(Array->Count < Array->CountMax);
    u32 Index = Array->Count++;
    Array->Values[Index] = Value;
    return Index;
}

internal void
AnimLayerArray_Remove(anim_layer_array* Array, u32 Index)
{
    Assert(Index < Array->Count);
    for (u32 i = Index; i < Array->Count - 1; i++)
    {
        Array->Values[i] = Array->Values[i + 1];
    }
}

//////////////////////////
//
// Animation Array

internal animation_array
AnimationArray_Create(gs_memory_arena* Storage, u32 CountMax)
{
    animation_array Result = {0};
    Result.CountMax = CountMax;
    Result.Values = PushArray(Storage, animation, Result.CountMax);
    return Result;
}

internal animation_handle
AnimationArray_Push(animation_array* Array, animation Value)
{
    Assert(Array->Count < Array->CountMax);
    animation_handle Result = {0};
    Result.Index = Array->Count++;
    Array->Values[Result.Index] = Value;
    return Result;
}

internal animation*
AnimationArray_Get(animation_array Array, animation_handle Handle)
{
    animation* Result = 0;
    if (IsValid(Handle) && Handle.Index < (s32)Array.Count)
    {
        Result = Array.Values + Handle.Index;
    }
    return Result;
}

internal animation*
AnimationArray_GetSafe(animation_array Array, animation_handle Handle)
{
    Assert(IsValid(Handle));
    Assert(Handle.Index < (s32)Array.Count);
    return AnimationArray_Get(Array, Handle);
}

//////////////////////////
//
// Animation

internal handle
Animation_AddBlock(animation* Animation, u32 StartFrame, s32 EndFrame, animation_pattern_handle AnimationProcHandle, u32 LayerIndex)
{
    Assert(LayerIndex < Animation->Layers.Count);
    
    animation_block NewBlock = {0};
    NewBlock.Range.Min = StartFrame;
    NewBlock.Range.Max = EndFrame;
    NewBlock.AnimationProcHandle = AnimationProcHandle;
    NewBlock.Layer = LayerIndex;
    
    handle Handle = AnimBlockArray_Push(&Animation->Blocks_, NewBlock);
    return Handle;
}

internal void
Animation_RemoveBlock(animation* Animation, handle AnimHandle)
{
    AnimBlockArray_Remove(&Animation->Blocks_, AnimHandle);
}

internal animation_block*
Animation_GetBlockFromHandle(animation* Animation, handle AnimHandle)
{
    animation_block* Result = 0;
    
    if (AnimHandle.Generation != 0 &&
        Animation->Blocks_.Generations[AnimHandle.Index] == AnimHandle.Generation)
    {
        Result = Animation->Blocks_.Values + AnimHandle.Index;
    }
    
    return Result;
}

internal u32
Animation_AddLayer(animation* Animation, anim_layer Layer)
{
    return AnimLayerArray_Push(&Animation->Layers, Layer);
}

internal u32
Animation_AddLayer (animation* Animation, gs_string Name, blend_mode BlendMode, animation_system* System)
{
    anim_layer NewLayer = {0};
    NewLayer.Name = PushStringF(System->Storage, 256, "%S", Name);
    NewLayer.BlendMode = BlendMode;
    
    return Animation_AddLayer(Animation, NewLayer);
}

internal void
Animation_RemoveLayer (animation* Animation, u32 LayerIndex)
{
    AnimLayerArray_Remove(&Animation->Layers, LayerIndex);
    for (u32 i = Animation->Blocks_.Count - 1; i >= 0; i--)
    {
        animation_block* Block = Animation->Blocks_.Values + i;
        if (Block->Layer > LayerIndex)
        {
            Block->Layer -= 1;
        }
        else if (Block->Layer == LayerIndex)
        {
            AnimBlockArray_RemoveAt(&Animation->Blocks_, i);
        }
    }
}

//////////////////////////
//
//

internal u32
SecondsToFrames(r32 Seconds, animation_system System)
{
    u32 Result = Seconds * (1.0f / System.SecondsPerFrame);
    return Result;
}

inline bool
FrameIsInRange(frame_range Range, s32 Frame)
{
    bool Result = (Frame >= Range.Min) && (Frame <= Range.Max);
    return Result;
}

internal u32
GetFrameCount(frame_range Range)
{
    u32 Result = (u32)Max(0, Range.Max - Range.Min);
    return Result;
}

internal r32
FrameToPercentRange(s32 Frame, frame_range Range)
{
    r32 Result = (r32)(Frame - Range.Min);
    Result = Result / GetFrameCount(Range);
    return Result;
}

internal s32
PercentToFrameInRange(r32 Percent, frame_range Range)
{
    s32 Result = Range.Min + (s32)(Percent * GetFrameCount(Range));
    return Result;
}

internal s32
ClampFrameToRange(s32 Frame, frame_range Range)
{
    s32 Result = Frame;
    if (Result < Range.Min)
    {
        Result = Range.Min;
    }
    else if (Result > Range.Max)
    {
        Result = Range.Max;
    }
    return Result;
}

// Blocks

// Layers

// Fade Group

internal bool
AnimationFadeGroup_ShouldRender (animation_fade_group FadeGroup)
{
    return IsValid(FadeGroup.From);
}

internal void
AnimationFadeGroup_Advance(animation_fade_group* Group)
{
    Group->From = Group->To;
    Clear(&Group->To);
    Group->FadeElapsed = 0;
    Group->FadeDuration = 0;
}

internal void
AnimationFadeGroup_Update(animation_fade_group* Group, r32 DeltaTime)
{
    if (IsValid(Group->To))
    {
        Group->FadeElapsed += DeltaTime;
        if (Group->FadeElapsed >= Group->FadeDuration)
        {
            AnimationFadeGroup_Advance(Group);
        }
    }
}

internal void
AnimationFadeGroup_FadeTo(animation_fade_group* Group, animation_handle To, r32 Duration)
{
    // complete current fade if there is one in progress
    if (IsValid(Group->To))
    {
        AnimationFadeGroup_Advance(Group);
    }
    
    Group->To = To;
    Group->FadeDuration = Duration;
}

// System

struct animation_system_desc
{
    gs_memory_arena* Storage;
    u32 AnimArrayCount;
    r32 SecondsPerFrame;
};

internal animation_system
AnimationSystem_Init(animation_system_desc Desc)
{
    animation_system Result = {};
    Result.Storage = Desc.Storage;
    Result.Animations = AnimationArray_Create(Result.Storage, Desc.AnimArrayCount);
    Result.SecondsPerFrame = Desc.SecondsPerFrame;
    
    Clear(&Result.ActiveFadeGroup.From);
    Clear(&Result.ActiveFadeGroup.To);
    Result.ActiveFadeGroup.FadeElapsed = 0;
    
    return Result;
}

internal animation*
AnimationSystem_GetActiveAnimation(animation_system* System)
{
    return AnimationArray_Get(System->Animations, System->ActiveFadeGroup.From);
}

internal animation_frame
AnimationSystem_CalculateAnimationFrame(animation_system* System,
                                        animation* Animation,
                                        gs_memory_arena* Arena)
{
    animation_frame Result = {0};
    Result.LayersCount = Animation->Layers.Count;
    Result.Layers = PushArray(Arena, animation_layer_frame, Result.LayersCount);
    ZeroArray(Result.Layers, animation_layer_frame, Result.LayersCount);
    
    for (u32 l = 0; l < Animation->Layers.Count; l++)
    {
        animation_layer_frame* Layer = Result.Layers + l;
        Layer->BlendMode = Animation->Layers.Values[l].BlendMode;
    }
    
    for (u32 i = 0; i < Animation->Blocks_.Count; i++)
    {
        animation_block Block = Animation->Blocks_.Values[i];
        
        if (FrameIsInRange(Block.Range, System->CurrentFrame))
        {
            animation_layer_frame* Layer = Result.Layers + Block.Layer;
            if (Layer->HasHot)
            {
                // NOTE(pjs): With current implementation, we don't allow
                // animations to hvae more than 2 concurrent blocks in the
                // timeline
                Assert(!Layer->HasNextHot);
                
                // NOTE(pjs): Make sure that Hot comes before NextHot
                if (Layer->Hot.Range.Min < Block.Range.Min)
                {
                    Layer->NextHot = Block;
                }
                else
                {
                    Layer->NextHot = Layer->Hot;
                    Layer->Hot = Block;
                }
                Layer->HasNextHot = true;
                
                frame_range BlendRange = {};
                BlendRange.Min = Layer->NextHot.Range.Min;
                BlendRange.Max = Layer->Hot.Range.Max;
                Layer->NextHotOpacity = FrameToPercentRange(System->CurrentFrame, BlendRange);
            }
            else
            {
                Layer->Hot = Block;
                Layer->NextHotOpacity = 0.0f;
                Layer->HasHot = true;
            }
        }
    }
    
    return Result;
}

internal void
AnimationSystem_Update(animation_system* System, r32 DeltaTime)
{
    if (!System->TimelineShouldAdvance) { return; }
    if (!AnimationFadeGroup_ShouldRender(System->ActiveFadeGroup)) { return; }
    
    AnimationFadeGroup_Update(&System->ActiveFadeGroup, DeltaTime);
    
    animation* ActiveAnim = AnimationSystem_GetActiveAnimation(System);
    // TODO(Peter): Revisit this. This implies that the framerate of the animation system
    // is tied to the framerate of the simulation. That seems correct to me, but I'm not sure
    System->CurrentFrame += 1;
    
    // Loop back to the beginning
    if (System->CurrentFrame > ActiveAnim->PlayableRange.Max)
    {
        switch (System->RepeatMode)
        {
            case AnimationRepeat_Single:
            {
                System->CurrentFrame = 0;
            }break;
            
            case AnimationRepeat_Loop:
            {
                // TODO(pjs):
            }break;
            
            InvalidDefaultCase;
        }
    }
}

inline bool
AnimationSystem_NeedsRender(animation_system System)
{
    bool Result = (System.CurrentFrame != System.LastUpdatedFrame);
    return Result;
}

#define FOLDHAUS_ANIMATION
#endif // FOLDHAUS_ANIMATION