#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

#include "debug.h"
#include "code.h"
#include "mem.h"
#include "desc.h"

// For compressing the source code a bit

#define follow_thunk(thunk) if (thunk->desc == (Desc*) __FORWARD_PTR__) thunk = thunk->_forward_ptr;

#define forward_thunk(thunk, frame_ptr) \
        Thunk* dst = get_dst(frame_ptr); \
        if(dst != NULL) \
        { \
            dst->desc = (Desc*) __FORWARD_PTR__; \
            dst->_forward_ptr = thunk; \
        }

#define arg_from_thunk(desc, arg) \
        if(((FunEntry*) (desc))->strictness & argmask) \
        { \
            push_a(eval(arg)); \
        } \
        else \
        { \
            push_a(arg); \
        } \
        argmask <<= 1;

#define arg_from_code(descarg, arg) \
        if(((FunEntry*) (descarg))->strictness & argmask) \
        { \
            Thunk* phl = alloc_b(); \
            phl->desc = (Desc*) __STACK_PLACEHOLDER__; \
            push_a(phl); \
            exec(arg, frame_ptr, stack_top_a, stack_top_b); \
        } \
        else \
        { \
            push_a(create_thunk(arg, frame_ptr)); \
        } \
        argmask <<= 1;


struct Thunk* create_thunk(Code* expr, int frame_ptr)
{
    assert(expr != NULL);
    
    // TODO: check over application
    // TODO: enforce strictness in ADT/Record
        
    switch (expr->type) {
    case CT_APP:
    {
        Thunk* thunk = createF(((AppEntry*) expr)->f);

        assert(thunk->desc->arity == expr->nr_args);

        for (int i = 0; i < expr->nr_args; i++) {
            thunk->_args[i] = create_thunk(((AppEntry*) expr)->args[i], frame_ptr);
        }

        return thunk;                    
    }
    case CT_APP_DYN:
    {
        Thunk* basethunk = local(frame_ptr, ((AppEntry*)expr)->var.index);
        if(!((AppEntry*)expr)->var.base.strict) basethunk = eval(basethunk);

        Desc* slice =
                get_slice(basethunk->desc->type == FT_SLICE ?
                          ((SliceEntry*) basethunk->desc)->forward_ptr : basethunk->desc, basethunk->desc->arity + expr->nr_args);

        Thunk* thunk = createF(slice);

        assert(thunk->desc->arity == basethunk->desc->arity + expr->nr_args);            

        for (int i = 0; i < basethunk->desc->arity; i++) {
            thunk->_args[i] = basethunk->_args[i];
        }

        for (int i = 0; i < expr->nr_args; i++) {
            thunk->_args[basethunk->desc->arity + i] 
                    = create_thunk(((AppEntry*) expr)->args[i], frame_ptr);
        }

        return thunk;
    }
    case CT_VAR:
        return local(frame_ptr, ((VarEntry*) expr)->index);
    case CT_VAR_STRICT: 
    {
        Thunk* arg = local(frame_ptr, ((VarEntry*) expr)->index);
        
        if(arg->desc->unboxable)
        {
            return createT(arg);
        }
        else
        {
            return arg;
        }
    }
    case CT_THUNK:
        return &((ThunkEntry*) expr)->thunk;
    case CT_SELECT:
    case CT_IF:
        // Only here to avoid intervalum check at switch 
        abort("Unexpected code type");
    }
}

void exec(Code* expr, int frame_ptr, int root_frame_ptr, int root_frame_ptr_b)
{
    while(1)
    {
        assert(expr != NULL);
        assert(stack_top_a < STACK_SIZE_A);

        // TODO: check over application
        // TODO: enforce strictness in ADT/Record
        
        switch (expr->type) {
        case CT_APP:
        {
            Desc* slice = ((AppEntry*) expr)->f;

            switch (slice->type) {
            case FT_PRIM:
            {
                for (int i = 0; i < expr->nr_args; i++) {
                    push_a(alloc_b());                        
                    exec(((AppEntry*) expr)->args[i], frame_ptr, stack_top_a, stack_top_b);
                }

                ((PrimEntry*) slice)->exec(root_frame_ptr);
                destroy_stack_frame(root_frame_ptr);
                destroy_stack_frame_b(root_frame_ptr_b);
                return;
            }
            case FT_FUN:
            {
                int new_frame_ptr = stack_top_a;
                int argmask = 1;

                for (int i = 0; i < expr->nr_args; i++) {
                    arg_from_code(slice, ((AppEntry*) expr)->args[i]);
                }

                expr = ((FunEntry*) slice)->body;
                frame_ptr = new_frame_ptr;
                continue;
            }
            case FT_SLICE:
            case FT_ADT:
            case FT_RECORD:
            {
                Thunk* thunk = updateF(get_dst(root_frame_ptr), slice);

                assert(thunk->desc->arity == expr->nr_args);

                for (int i = 0; i < expr->nr_args; i++) {
                    thunk->_args[i] 
                            = create_thunk(((AppEntry*) expr)->args[i], frame_ptr);
                }

                set_return(root_frame_ptr, thunk);
                destroy_stack_frame(root_frame_ptr);
                destroy_stack_frame_b(root_frame_ptr_b);
                return;                    
            }
            case FT_BOXED_LIT:
                abort("Literal unexpected here");
            case FT_CAF:
            case FT_CAF_REDUCED:
                not_implemented("CAF");
            }
        }                        
        case CT_APP_DYN:
        {
            Thunk* basethunk = local(frame_ptr, ((AppEntry*)expr)->var.index);
            if(!((AppEntry*)expr)->var.base.strict) basethunk = eval(basethunk);

            Desc* slice =
                    get_slice(basethunk->desc->type == FT_SLICE ?
                              ((SliceEntry*) basethunk->desc)->forward_ptr : basethunk->desc, basethunk->desc->arity + expr->nr_args);

            switch(slice->type) {
            case FT_PRIM:
            {
                for (int i = 0; i < basethunk->desc->arity; i++) {
                    push_a(eval(basethunk->_args[i]));
                }

                for (int i = 0; i < expr->nr_args; i++) {
                    push_a(alloc_b());
                    exec(((AppEntry*) expr)->args[i], frame_ptr, stack_top_a, stack_top_b);
                } 

                ((PrimEntry*) slice)->exec(root_frame_ptr);
                destroy_stack_frame(root_frame_ptr);
                destroy_stack_frame_b(root_frame_ptr_b);                
                return;                    
            }
            case FT_FUN:
            {
                int new_frame_ptr = stack_top_a;                    
                int argmask = 1;

                for (int i = 0; i < basethunk->desc->arity; i++) {
                    arg_from_thunk(slice, basethunk->_args[i])
                }

                for (int i = 0; i < expr->nr_args; i++) {
                    arg_from_code(slice, ((AppEntry*) expr)->args[i]);    
                } 

                expr = ((FunEntry*) slice)->body;
                frame_ptr = new_frame_ptr;
                continue;                    
            }
            case FT_SLICE:
            case FT_ADT:
            case FT_RECORD:
            {
                Thunk* thunk = updateF(get_dst(root_frame_ptr), slice);

                assert(thunk->desc->arity == basethunk->desc->arity + expr->nr_args);            

                for (int i = 0; i < basethunk->desc->arity; i++) {
                    thunk->_args[i] = basethunk->_args[i];
                }

                for (int i = 0; i < expr->nr_args; i++) {
                    thunk->_args[basethunk->desc->arity + i] 
                            = create_thunk(((AppEntry*) expr)->args[i], frame_ptr);
                }

                set_return(root_frame_ptr, thunk);
                destroy_stack_frame(root_frame_ptr);
                destroy_stack_frame_b(root_frame_ptr_b);
                return;                    
            }
            case FT_BOXED_LIT:
                abort("Literal unexpected here");                
            case FT_CAF:
            case FT_CAF_REDUCED:
                not_implemented("CAF");
            }
        }
        case CT_VAR_STRICT:
        {
            Thunk* arg = local(frame_ptr, ((VarEntry*) expr)->index);
            
            assert(is_hnf(arg));

            if(arg->desc->unboxable)
            {
                arg = updateT(get_dst(root_frame_ptr), arg);
            }
            else
            {
                forward_thunk(arg, root_frame_ptr);
            }
            
            set_return(root_frame_ptr, arg);
            destroy_stack_frame(root_frame_ptr);
            destroy_stack_frame_b(root_frame_ptr_b);            
            return;                    
        }
        case CT_VAR:
        {
            Thunk* thunk = local(frame_ptr, ((VarEntry*) expr)->index);

            follow_thunk(thunk);
            forward_thunk(thunk, root_frame_ptr);            
            set_return(root_frame_ptr, thunk);

            switch(thunk->desc->type) {
            case FT_FUN:
            {
                // Destroy stack frame before eval, it is not needed any more
                // Greatly reduces stack usage
                destroy_stack_frame(root_frame_ptr);
                destroy_stack_frame_b(root_frame_ptr_b);  
                frame_ptr = stack_top_a;
                // Here frame_ptr == root_frame_ptr

                int argmask = 1;

                for (int i = 0; i < thunk->desc->arity; i++) {
                    arg_from_thunk(thunk->desc, thunk->_args[i]);
                }

                expr = ((FunEntry*) thunk->desc)->body;
                continue;
            }
            case FT_PRIM:
            {

                for (int i = 0; i < thunk->desc->arity; i++) {
                    push_a(eval(thunk->_args[i]));
                }

                ((PrimEntry*) thunk->desc)->exec(root_frame_ptr);
                
                destroy_stack_frame(root_frame_ptr);
                destroy_stack_frame_b(root_frame_ptr_b);
                return;
            }
            case FT_CAF:
            case FT_CAF_REDUCED:
                not_implemented("CAF");            
            case FT_SLICE:
            case FT_ADT:
            case FT_RECORD:
            case FT_BOXED_LIT:
                destroy_stack_frame(root_frame_ptr);
                destroy_stack_frame_b(root_frame_ptr_b);
                return;
            }            
        }
        case CT_THUNK:
        {
            Thunk* thunk = &((ThunkEntry*) expr)->thunk;            
            forward_thunk(thunk, root_frame_ptr);            
            set_return(root_frame_ptr, thunk);
            destroy_stack_frame(root_frame_ptr);
            destroy_stack_frame_b(root_frame_ptr_b);
            return;               
        }
        case CT_SELECT:
        {
            push_a(NULL);
            exec(((SelectEntry*) expr)->expr, frame_ptr, stack_top_a, stack_top_b);
            Thunk* pattern = pop_a();

            assert(is_hnf(pattern));
            assert(pattern->desc->type == FT_ADT);            

            bool handled = false;
            
            for (int i = 0; i < expr->nr_cases; i++) {
                SelectCaseEntry* caseEntry = &((SelectEntry*) expr)->cases[i];
                
                if (caseEntry->type == SC_CONS) {
                    // Pattern match
                    if ((Desc*) caseEntry->cons != pattern->desc) continue;

                    // Put the constructor arguments to the stack if matches
                    for (int i = 0; i < pattern->desc->arity; i++) {
                        push_a(pattern->_args[i]);
                    }                  
                }
                else if (caseEntry->type == SC_LIT) {
                    printf("Exec: Unhandled entry type in CT_SELECT (SC_LIT)");
                    exit(-1);
                }
                
                // must be SC_DEFAULT now
                handled = true;
                expr = caseEntry->body;
                break;
            }

            if(handled) continue;
            
            printf("Exec: no select cases matches");
            print(pattern, false);
            exit(-1);
        }
        case CT_IF:
        {        
            push_a(alloc_b());
            exec(((IfEntry*) expr)->cond, frame_ptr, stack_top_a, stack_top_b);
            Thunk* cond = pop_a();
            
            if (readB(cond)) {
                expr = ((IfEntry*) expr)->texpr;
                continue;                
            }
            else {
                expr = ((IfEntry*) expr)->fexpr;
                continue;     
            }
        }
        }
    }
}

struct Thunk* eval(Thunk* thunk) {
    assert(thunk != NULL);    
    
    follow_thunk(thunk);
    
    switch(thunk->desc->type) {
    case FT_FUN:
    {
        push_a(thunk);
        int frame_ptr = stack_top_a;
        int argmask = 1;
        
        for (int i = 0; i < thunk->desc->arity; i++) {
            arg_from_thunk(thunk->desc, thunk->_args[i]);
        }
        
        exec(((FunEntry*) thunk->desc)->body, frame_ptr, frame_ptr, stack_top_b);
        thunk = pop_a();
        return thunk;
    }
    case FT_PRIM:
    {
        push_a(thunk);
        int frame_ptr = stack_top_a;

        for (int i = 0; i < thunk->desc->arity; i++) {
            push_a(eval(thunk->_args[i]));
        }

        ((PrimEntry*) thunk->desc)->exec(frame_ptr);        
        
        stack_top_a = frame_ptr;        
        thunk = pop_a();
        return thunk;
    }
    case FT_CAF:
    case FT_CAF_REDUCED:
        not_implemented("CAF");            
    case FT_SLICE:
    case FT_ADT:
    case FT_RECORD:
    case FT_BOXED_LIT:
        return thunk;
    }
}