#pragma once
#include "macros.hpp"
#include "types.hpp"
#include "print.hpp"
#include "bucket_allocator.hpp"
#include "arraylist.hpp"
#include "stacktrace.hpp"

namespace Scheduler {

    // NOTE(Felix): since we want to be able to interpolate any data in
    //   principle, and the animation needs the start and end values, but the
    //   size of the stuff we want to interpolate may vary, we just give it a
    //   small chunk of memory to be stored
    typedef s64 Data_Block[22];


    typedef void (*Closure_F)(Data_Block);
    typedef void (*Lambda_F)();

    typedef f32  (*Shaper_F)(f32 t);
    typedef void (*Interpolator_F)(void* from, f32 t, void* to, void* interpolant);

    enum struct Interpolation_Type : u8 {
        Lerp = 1 << 7,
        Ease_In,
        Ease_Out,
        Ease_Middle,
        Ease_In_And_Out
    };

    enum struct Interpolant_Type : u8 {
        F32 = 1 << 7,
    };


    struct Scheduled_Animation_Create_Info {
        float seconds_to_start;
        float seconds_to_end;

        void* interpolant;
        Interpolant_Type interpolant_type;

        void* from;
        void* to;

        Interpolation_Type interpolation_type = Interpolation_Type::Lerp;
        const char* name = "";
    };


    enum struct Function_Type {
        Closure,
        Lambda
    };

    struct Action_Create_Info {
        Function_Type type;
        union {
            Lambda_F  lambda;
            Closure_F closure;
        };
        void* param      = nullptr;
        u32   param_size = 0;
        const char* name = "";
    };

    struct Scheduled_Action_Create_Info {
        float seconds_to_run;
        Action_Create_Info action;
    };

    struct Action {
        Function_Type type;
        union {
            Lambda_F  lambda;
            Closure_F closure;
        };
        Data_Block    param;
        Action*       next;
        u64           creation_stamp;
        bool          already_ran;
#ifdef FTB_INTERNAL_DEBUG
        const char* name;
#endif
    };

    struct Scheduled_Action {
        f32    seconds_to_run;
        Action action;
    };

    struct Scheduled_Animation {
        Interpolation_Type interpolation_type;
        Interpolant_Type   interpolant_type;

        f32 seconds_to_start;
        f32 seconds_to_end;

        void* interpolant;

        Data_Block from;
        Data_Block to;

        Action* next;
#ifdef FTB_INTERNAL_DEBUG
        const char* name;
#endif
    };

    enum struct Schedulee_Type : u8 {
        None,
        Action,
        Animation,
    };

    struct Action_Or_Animation {
        Schedulee_Type type;
        union {
            Action* action;
            Scheduled_Animation* animation;
        };
    };

    // For user defined shapers t -> t
    Shaper_F       _shapers[127];
    // Interpolators for user types
    Interpolator_F _interpolators[127];
    size_t         _interpolatee_sizes[127];

    // Per reset cycle:
    // PING
    Bucket_Allocator<Scheduled_Animation> active_animations_1;
    Bucket_Allocator<Scheduled_Action>    scheduled_actions_1;
    Bucket_Allocator<Action>              chained_actions_1;
    // PONG
    Bucket_Allocator<Scheduled_Animation> active_animations_2;
    Bucket_Allocator<Scheduled_Action>    scheduled_actions_2;
    Bucket_Allocator<Action>              chained_actions_2;

    Bucket_Allocator<Scheduled_Animation>* active_animations;
    Bucket_Allocator<Scheduled_Action>*    scheduled_actions;
    Bucket_Allocator<Action>*              chained_actions;

    Bucket_Allocator<Scheduled_Animation>* future_active_animations;
    Bucket_Allocator<Scheduled_Action>*    future_scheduled_actions;
    Bucket_Allocator<Action>*              future_chained_actions;

    // Per Tick:
    // if something is deleted while iterating over them
    Array_List<Scheduled_Animation*> _animations_marked_for_deletion;
    Array_List<Scheduled_Action*>       _actions_marked_for_deletion;

    Array_List<Action*> _chained_actions_to_be_run_after_iteration;

    bool _is_iterating = false;
    bool _should_reset = false;
    bool _should_stop_iterating = false;
    u64 _action_stamp_counter = 0;

    auto init() -> void {
        active_animations_1.alloc();
        scheduled_actions_1.alloc();
        chained_actions_1.alloc();

        active_animations_2.alloc();
        scheduled_actions_2.alloc();
        chained_actions_2.alloc();

        active_animations = &active_animations_1;
        scheduled_actions = &scheduled_actions_1;
        chained_actions   = &chained_actions_1;

        future_active_animations = &active_animations_2;
        future_scheduled_actions = &scheduled_actions_2;
        future_chained_actions   = &chained_actions_2;


        _animations_marked_for_deletion.alloc();
        _actions_marked_for_deletion.alloc();
        _chained_actions_to_be_run_after_iteration.alloc(20);
    }

    auto deinit() -> void {
        active_animations_1.dealloc();
        scheduled_actions_1.dealloc();
        chained_actions_1.dealloc();

        active_animations_2.dealloc();
        scheduled_actions_2.dealloc();
        chained_actions_2.dealloc();

        _animations_marked_for_deletion.dealloc();
        _actions_marked_for_deletion.dealloc();
        _chained_actions_to_be_run_after_iteration.dealloc();
    }

    auto register_shaper(Shaper_F f, Interpolation_Type t) {
        _shapers[(u8)t] = f;
    }

    auto register_interpolator(Interpolator_F f, Interpolant_Type t, size_t size_of_interpolant) {
        _interpolatee_sizes[(u8)t] = size_of_interpolant;
        _interpolators[(u8)t] = f;
    }

    auto schedule_animation(Scheduled_Animation_Create_Info aci) -> Scheduled_Animation* {
        Scheduled_Animation* anim;
        if (_should_reset) {
            anim = future_active_animations->allocate();
        } else {
            anim = active_animations->allocate();
        }

        anim->next = nullptr;

#ifdef FTB_INTERNAL_DEBUG
       anim->name = aci.name;
#endif

        anim->interpolation_type = aci.interpolation_type;
        anim->interpolant_type   = aci.interpolant_type;

        anim->seconds_to_start = aci.seconds_to_start;
        anim->seconds_to_end   = aci.seconds_to_end;

        anim->interpolant = aci.interpolant;

        u32 data_size;
        switch(anim->interpolant_type) {
            case Interpolant_Type::F32:  data_size = sizeof(f32); break;
            default: {
                data_size = _interpolatee_sizes[(u8)(anim->interpolant_type)];
                panic_if(data_size == 0, "Interpolatee (%d) size was 0 (was it initialized correctly)?",
                         anim->interpolant_type);
            }
        }

        memcpy(&anim->from, aci.from, data_size);
        memcpy(&anim->to,   aci.to,   data_size);

        return anim;
    }

    auto advance_single_animation(Scheduled_Animation* anim) -> void {
        // if not yet started, skip
        if (anim->seconds_to_start > 0)
            return;

        // otherwise run it:
        f32 perf_diff = anim->seconds_to_end - anim->seconds_to_start;
        f32 perf_inside = -anim->seconds_to_start;
        f64 t = 1.0 * perf_inside / perf_diff;

        switch (anim->interpolation_type) {
            case Interpolation_Type::Lerp: break;
            case Interpolation_Type::Ease_In: {
                t *= t;
            } break;
            case Interpolation_Type::Ease_Out: {
                t = -(t * (t - 2));
            } break;
            case Interpolation_Type::Ease_In_And_Out: {
                // NOTE(Felix): yes -- Mon Dec  7 11:47:34 2020
                t = (t < 0.5) ?
                    +2 * t * t :
                    -2 * (t * (t - 2)) - 1;
            } break;
            case Interpolation_Type::Ease_Middle: {
                // t = (t < 0.5) ?
                //     -2 * t * (t - 1) :
                //     +2 * t * (t - 1) + 1;
                t = 4.0f / 5.0f * t*t*t - 6.0f/5.0f *t*t + 7.0f/5.0f * t;
            } break;
            default: {
                // try user supported shaper
                Shaper_F shaper = _shapers[(u8)anim->interpolant_type];

                panic_if(shaper == nullptr,
                         "Shaper function for type (%d) was nullptr (was it initialized correctly)?",
                         anim->interpolation_type);

                t = shaper(t);
            }
        }

        switch(anim->interpolant_type) {
            case Interpolant_Type::F32: {
                f32 from = *((f32*)&anim->from);
                f32 to   = *((f32*)&anim->to);
                *((f32*)anim->interpolant) = from + (to - from) * t;
            } break;
            default: {
                // try user supported interpolator
                Interpolator_F interpolator = _interpolators[(u8)anim->interpolant_type];

                panic_if(interpolator == nullptr,
                         "Interpolator function for type (%d) was nullptr (was it initialized correctly)?",
                         anim->interpolant_type);

                interpolator(&anim->from, t, &anim->to, anim->interpolant);
            }
        }
    }

    auto _init_action(Action* action, Action_Create_Info aci) -> void {
        action->next = nullptr;
#ifdef FTB_INTERNAL_DEBUG
        action->name = aci.name;
#endif
        action->creation_stamp = _action_stamp_counter;

        ++_action_stamp_counter;
        action->already_ran = false;

        if (aci.param) {
            if(aci.param_size > sizeof(Data_Block)) {
                panic("%llu (sizeof(Data_Block)) < %u (aci.param_size)",
                      sizeof(Data_Block), aci.param_size);
            }
            action->type = Function_Type::Closure;
            action->closure = aci.closure;
            memcpy(&action->param, aci.param, aci.param_size);
        } else {
            action->type = Function_Type::Lambda;
            action->lambda = aci.lambda;
            memset(&action->param, 0, sizeof(Data_Block));
        }

        if      (aci.type == Function_Type::Lambda)  action->lambda  = aci.lambda;
        else if (aci.type == Function_Type::Closure) action->closure = aci.closure;

    }

    auto schedule_action(Scheduled_Action_Create_Info aci) -> Scheduled_Action* {
        Scheduled_Action* scheduled_action;
        if (_should_reset) {
            scheduled_action = future_scheduled_actions->allocate();
        } else {
            scheduled_action = scheduled_actions->allocate();
        }

        scheduled_action->seconds_to_run = aci.seconds_to_run;
        _init_action(&scheduled_action->action, aci.action);
        debug_log("scheduling action %s %d", aci.action.name, scheduled_action->action.creation_stamp);
        return scheduled_action;
    }


    auto _actually_reset() {
        debug_log("HARD RESET SCHEDULER");
        _should_reset = false;
        active_animations->clear();
        scheduled_actions->clear();
        chained_actions->clear();
        _animations_marked_for_deletion.clear();
        _actions_marked_for_deletion.clear();

        // swap ping pong
        Bucket_Allocator<Scheduled_Animation>* t_active_animations = active_animations;
        Bucket_Allocator<Scheduled_Action>*    t_scheduled_actions = scheduled_actions;
        Bucket_Allocator<Action>*              t_chained_actions   = chained_actions;

        active_animations = future_active_animations;
        scheduled_actions = future_scheduled_actions;
        chained_actions   = future_chained_actions;

        future_active_animations = t_active_animations;
        future_scheduled_actions = t_scheduled_actions;
        future_chained_actions   = t_chained_actions;
    }

    auto reset() -> void {
        if (_is_iterating) {
            debug_log("SOFT RESET Scheduler");
            _should_reset = true;
            future_active_animations->clear();
            future_scheduled_actions->clear();
            future_chained_actions->clear();
        }
        else
            _actually_reset();
    }

    auto chain_action(Scheduled_Animation* existing_animation, Action_Create_Info aci) -> Action* {
        Action* chain_action;
        if (_should_reset) {
            chain_action = future_chained_actions->allocate();
        } else {
            chain_action = chained_actions->allocate();
        }

        _init_action(chain_action, aci);

        existing_animation->next = chain_action;
        return chain_action;
    }

    auto chain_action(Action* existing_action, Action_Create_Info aci) -> Action* {
        Action* chain_action;
        if (_should_reset) {
            chain_action = future_chained_actions->allocate();
        } else {
            chain_action = chained_actions->allocate();
        }

        _init_action(chain_action, aci);

        existing_action->next = chain_action;
        return chain_action;
    }

    inline auto chain_action(Action_Or_Animation aoa, Action_Create_Info aci) -> Action* {
        if (aoa.type == Schedulee_Type::Action)
            return chain_action(aoa.action, aci);
        else if (aoa.type == Schedulee_Type::Animation)
            return chain_action(aoa.animation, aci);
        else if (aoa.type == Schedulee_Type::None) {
            Scheduled_Action* sa = schedule_action({
                .seconds_to_run = 0.0f,
                .action { aci }
            });
            return &sa->action;
        } else {
            panic("unknown Schedulee type");
            return nullptr;
        }
    }

    inline auto execute_action(Action* action) -> void {
        debug_log("running action %s %d", action->name, action->creation_stamp);

        action->already_ran = true;
        if (action->type == Function_Type::Closure) {
            action->closure(action->param);
        } else {
            action->lambda();
        }

        debug_log("finished running action %s %d", action->name, action->creation_stamp);
    }

    auto handle_chained_action(Action* action) -> void {
        debug_log("Handling chained actions");
        while (action) {
            debug_log("RUNNING CHAINED %s %d", action->name, action->creation_stamp);
            execute_action(action);

            debug_log("DELETING action %s %d", action->name, action->creation_stamp);
            chained_actions->free_object(action);
            action = action->next;

            if (_should_stop_iterating) break;
        }
        debug_log("Chained actions done");
    }

    auto run_pending_actions_and_reset() -> void {
        Auto_Array_List<Action*> pending_actions(16);

        debug_log("%{color<}Running pending actions:", console_cyan);
        scheduled_actions->for_each([&](Scheduled_Action* s_action) {
            if (!s_action->action.already_ran) {
                pending_actions.append(&s_action->action);
            }
        });

        active_animations->for_each([&](Scheduled_Animation* s_animation) {
            if (s_animation->next && !s_animation->next->already_ran) {
                pending_actions.append(s_animation->next);
            }
        });

        qsort(pending_actions.data,
              pending_actions.count,
              sizeof(pending_actions.data[0]),
              [] (const void* a1, const void* a2) -> int {
                  return (*((Action**)(a1)))->creation_stamp - (*((Action**)(a2)))->creation_stamp;
              });

        for (auto action : pending_actions) {
            execute_action(action);
        }

        debug_log("pending_actions done%{>color}");
        _should_stop_iterating = true;
        reset();
    }

    auto update_all(f32 delta_time) -> void {

        // advance animations and collect due actions
        {
            active_animations->for_each([=](Scheduled_Animation* anim) {
                anim->seconds_to_start -= delta_time;
                anim->seconds_to_end   -= delta_time;

                advance_single_animation(anim);

                if (anim->seconds_to_end <= 0) {
                    // NOTE(Felix): if already finished snap the value to its target
                    //   and delete it
                    switch (anim->interpolant_type) {
                        case Interpolant_Type::F32:        *(f32*)anim->interpolant =       *(f32*)anim->to; break;
                        default: {
                            size_t interpolantee_size = _interpolatee_sizes[(u8)anim->interpolant_type];
                            panic_if(interpolantee_size == 0,
                                     "Interpolatee (%d) size was 0 (was it initialized correctly)?",
                                     anim->interpolant_type);

                            memcpy(anim->interpolant, anim->to, interpolantee_size);
                        }
                    }

                    _animations_marked_for_deletion.append(anim);
                    // NOTE(Felix): Don't actually run the next here, queue it
                    //   up for after the iteration, see note below.
                    if (anim->next) {
                        _chained_actions_to_be_run_after_iteration.append(anim->next);
                    }
                }
            });
            scheduled_actions->for_each([=](Scheduled_Action* action) {
                action->seconds_to_run -= delta_time;
                if (action->seconds_to_run <= 0) {
                    _chained_actions_to_be_run_after_iteration.append(&action->action);
                    _actions_marked_for_deletion.append(action);
                }
            });
        }


        // NOTE(Felix): The reason why we iterate over the chained actions like
        //   this: Imagine the following scenario: We schedule two animations
        //   that take the same time to run should run in parallel. So what you
        //   do for the first animation is put their parenting action (not the
        //   unparenting action) as the last action in the current game state
        //   and schedule their animation and then chain the unparenting action
        //   to the animation. The gamestate however only knows about the
        //   parenting action, so that the next thing that is scheduled runs
        //   parallel to it. For the second animation, the parenting action is
        //   scheduled onto the parenting action of the first animation, the
        //   animation is scheduled, and then also the unparenting action is
        //   chained to the animation. This time we set the Game_State
        //   last_scheduled to the unparenting action, so that no further
        //   animation will happen in parallel. Now imagine we chain some
        //   animation to the game state, that involves the animation of the
        //   first object. It can happen, when iterating through the animations,
        //   that we iterate first over the second animation, would then run
        //   their chained actions, in which we would animate the first object.
        //   This is bad, as they are not finished yet, their unparenting action
        //   did not run yet. Now we "solve" this by iterating breadth first
        //   over the actions.
        if (_chained_actions_to_be_run_after_iteration.count > 1) {
            qsort(_chained_actions_to_be_run_after_iteration.data,
                  _chained_actions_to_be_run_after_iteration.count,
                  sizeof(_chained_actions_to_be_run_after_iteration.data[0]),
                  [] (const void* a1, const void* a2) -> int {
                      return (*((Action**)(a1)))->creation_stamp - (*((Action**)(a2)))->creation_stamp;
                  });
        }
        // excute all due actions:
        {
            _is_iterating = true;
            _should_stop_iterating = false;
            for (Action* action : _chained_actions_to_be_run_after_iteration) {
                if (action->already_ran) continue;

                execute_action(action);

                if (_should_stop_iterating) break;

                handle_chained_action(action->next);

                if (_should_stop_iterating) break;
            }
            _is_iterating = false;
            _chained_actions_to_be_run_after_iteration.clear();
        }


        // NOTE(Felix): if Scheduler::reset was called in an action (happens
        //   when scheduling a level switch), then don't actually reset
        //   everyting, but only set _should_reset. Because if we would actually
        //   clear all the bucket allocators, we would then anyway call
        //   free_object on them down when we process the _marked_for_deletion
        //   things, so we would have stuff in the free list that is not
        //   actually allocated
        if (_should_reset) {
            _actually_reset();
        } else {
            // NOTE(Felix): Don't free stuff from the bucket_allocators while
            //   iterating over them, as this appends the pointers to the free_list,
            //   which then is no longer sorted, which destroys the mechanism to
            //   check if a bucket is active or freed, so for_each will be called
            //   for buckets that are no longer alive. -Felix Dec 18 2020
            for (auto anim : _animations_marked_for_deletion) {
                active_animations->free_object(anim);
            }
            for (auto action : _actions_marked_for_deletion) {
                scheduled_actions->free_object(action);
            }
            _animations_marked_for_deletion.clear();
            _actions_marked_for_deletion.clear();
        }
    }
}