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

#include "utils/Functions.h"
#include "vm/Operation.h"
#include "vm/Script.h"

void sError(Script* sc, const char* format, ...) {
    va_list args;
    va_start(args, format);
    vsnprintf(sc->error, SCRIPT_ERROR_SIZE, format, args);
    va_end(args);
}

static void sCannotSetValueType(Script* sc) {
    sError(sc, "cannot set value type");
}

static bool sRead(Script* sc, void* buffer, int length) {
    if(sc->readIndex + length > sc->code->length) {
        sError(sc, "cannot read expected %d bytes of data from bytecode",
               length);
        return true;
    }
    memcpy(buffer, sc->code->code + sc->readIndex, (size_t)length);
    sc->readIndex += length;
    return false;
}

static Operation sReadOperation(Script* sc) {
    unsigned char c;
    if(sRead(sc, &c, 1)) {
        return OP_NOTHING;
    }
    return (Operation)c;
}

static Value* sPeekStack(Script* sc, ValueType type) {
    if(sc->stackIndex <= 0) {
        sError(sc, "stack underflow");
        return NULL;
    }
    ValueType stackType = vGetType(sc->stack[sc->stackIndex - 1]);
    if(stackType != type) {
        sError(sc, "expected %s on stack but got %s", vtGetName(type),
               vtGetName(stackType));
        return NULL;
    }
    return sc->stack + (sc->stackIndex - 1);
}

bool sPopInt32(Script* sc, int32* i) {
    Value* v = sPeekStack(sc, VT_INT);
    if(v == NULL) {
        return true;
    }
    *i = v->data.intValue;
    sc->stackIndex--;
    return false;
}

bool sPopFloat(Script* sc, float* f) {
    Value* v = sPeekStack(sc, VT_FLOAT);
    if(v == NULL) {
        return true;
    }
    *f = v->data.floatValue;
    sc->stackIndex--;
    return false;
}

static bool sReadInt32(Script* sc, int32* i) {
    return sRead(sc, i, sizeof(int32));
}

static bool sReadFloat(Script* sc, float* f) {
    return sRead(sc, f, sizeof(float));
}

static Value* sPushStack(Script* sc, int values) {
    if(sc->stackIndex + values > SCRIPT_STACK_SIZE) {
        sError(sc, "stack overflow");
        return NULL;
    }
    Value* v = sc->stack + sc->stackIndex;
    for(int i = 0; i < values; i++) {
        if(vSetType(v + i, VT_NOT_SET)) {
            sCannotSetValueType(sc);
            return NULL;
        }
    }
    sc->stackIndex += values;
    return v;
}

bool sPushInt32(Script* sc, int32 i) {
    Value* v = sPushStack(sc, 1);
    if(vSetType(v, VT_INT)) {
        sCannotSetValueType(sc);
        return true;
    }
    v->data.intValue = i;
    return false;
}

bool sPushFloat(Script* sc, float f) {
    Value* v = sPushStack(sc, 1);
    if(vSetType(v, VT_FLOAT)) {
        sCannotSetValueType(sc);
        return true;
    }
    v->data.floatValue = f;
    return false;
}

static void sPushInt32Value(Script* sc) {
    int32 value = 0;
    if(!sReadInt32(sc, &value)) {
        sPushInt32(sc, value);
    }
}

static void sPushFloatValue(Script* sc) {
    float value = 0;
    if(!sReadFloat(sc, &value)) {
        sPushFloat(sc, value);
    }
}

#define ZERO_CHECK(name)                                                       \
    if(values[0] == 0) {                                                       \
        sError(sc, name " by 0");                                              \
        return;                                                                \
    }

#define OP_BASE(type, Type, RType, op, check)                                  \
    {                                                                          \
        type values[2];                                                        \
        if(!sPop##Type(sc, values) && !sPop##Type(sc, values + 1)) {           \
            check;                                                             \
            sPush##RType(sc, values[1] op values[0]);                          \
        }                                                                      \
    }

#define CHECKED_NUMBER_OP(type, Type, op, check)                               \
    OP_BASE(type, Type, Type, op, check)
#define NUMBER_OP(type, Type, op) CHECKED_NUMBER_OP(type, Type, op, )
#define BOOL_OP(type, Type, op) OP_BASE(type, Type, Int32, op, )
#define DIVISION(type, Type)                                                   \
    CHECKED_NUMBER_OP(type, Type, /, ZERO_CHECK("division"));
#define MODULE(type, Type)                                                     \
    CHECKED_NUMBER_OP(type, Type, %, ZERO_CHECK("module"));

#define INVERT_SIGN(type, Type)                                                \
    {                                                                          \
        type value = 0;                                                        \
        if(!sPop##Type(sc, &value)) {                                          \
            sPush##Type(sc, -value);                                           \
        }                                                                      \
    }

static void sReserveBytes(Script* sc) {
    int32 values = 0;
    int32 offset = 0;
    if(sReadInt32(sc, &values) || sReadInt32(sc, &offset)) {
        return;
    }
    int32 oldIndex = sc->stackVarIndex;
    sc->stackVarIndex = sc->stackIndex - offset;
    sPushStack(sc, values - offset);
    sPushInt32(sc, oldIndex);
}

static void sGlobalReserveBytes(Script* sc) {
    int32 values = 0;
    if(sReadInt32(sc, &values)) {
        return;
    }
    sc->stackVarIndex = sc->stackIndex;
    if(values >= 0) {
        sPushStack(sc, values);
    } else {
        sc->stackIndex += values;
        if(sc->stackIndex < 0) {
            sError(sc, "invalid global free %d", values);
        }
    }
}

static void sNot(Script* sc) {
    int32 value = 0;
    if(!sPopInt32(sc, &value)) {
        sPushInt32(sc, !value);
    }
}

static void sBitNotInt32(Script* sc) {
    int32 value = 0;
    if(!sPopInt32(sc, &value)) {
        sPushInt32(sc, ~value);
    }
}

static void sLine(Script* sc) {
    sRead(sc, &sc->line, 2);
}

static void sGoTo(Script* sc) {
    int32 gotoIndex;
    if(!sReadInt32(sc, &gotoIndex)) {
        sc->readIndex = gotoIndex;
    }
}

static void sGoSub(Script* sc) {
    int32 gotoIndex;
    int32 offset;
    if(sReadInt32(sc, &gotoIndex) || sReadInt32(sc, &offset)) {
        return;
    }
    int index = sc->stackIndex - offset - 1;
    if(index < 0 || index >= SCRIPT_STACK_SIZE) {
        sError(sc, "invalid gosub offset");
        return;
    } else if(vGetType(sc->stack[index]) != VT_INT) {
        sError(sc, "gosub expects an int got %s",
               vtGetName(vGetType(sc->stack[index])));
        return;
    }
    sc->stack[index].data.intValue = sc->readIndex;
    sc->readIndex = gotoIndex;
}

static void sReturn(Script* sc) {
    int32 values = 0;
    int32 varIndex = 0;
    if(sReadInt32(sc, &values) || sPopInt32(sc, &varIndex)) {
        return;
    }
    sc->stackVarIndex = varIndex;
    if(sc->stackIndex < values) {
        sError(sc, "invalid return index");
        return;
    }
    sc->stackIndex -= values;
    if(sPopInt32(sc, &sc->readIndex) || sc->readIndex < 0) {
        sError(sc, "read index is corrupt");
    }
}

static void sReturnPointer(Script* sc) {
    Value* v = sPeekStack(sc, VT_ARRAY);
    if(v == NULL) {
        return;
    }
    sc->stackIndex--;
    sReturn(sc);
    Value* p = sPushStack(sc, 1);
    if(p != NULL) {
        *p = *v;
    }
}

#define RETURN(type, Type)                                                     \
    {                                                                          \
        type value;                                                            \
        if(!sPop##Type(sc, &value)) {                                          \
            sReturn(sc);                                                       \
            sPush##Type(sc, value);                                            \
        }                                                                      \
    }

static void sIfGoTo(Script* sc) {
    int32 gotoIndex = 0;
    int32 value = false;
    if(!sReadInt32(sc, &gotoIndex) && !sPopInt32(sc, &value) && !value) {
        sc->readIndex = gotoIndex;
    }
}

static void sPeekFalseGoTo(Script* sc) {
    int32 gotoIndex = 0;
    if(sReadInt32(sc, &gotoIndex)) {
        return;
    }
    Value* v = sPeekStack(sc, VT_INT);
    if(v != NULL && v->data.intValue == 0) {
        sc->readIndex = gotoIndex;
    }
}

static void sPeekTrueGoTo(Script* sc) {
    int32 gotoIndex = 0;
    if(sReadInt32(sc, &gotoIndex)) {
        return;
    }
    Value* v = sPeekStack(sc, VT_INT);
    if(v != NULL && v->data.intValue != 0) {
        sc->readIndex = gotoIndex;
    }
}

static void sNewArray(Script* sc) {
    int32 length = 0;
    int32 size = 0;
    if(sReadInt32(sc, &size) || sPopInt32(sc, &length)) {
        return;
    }
    Value* p = sPushStack(sc, 1);
    if(vSetType(p, VT_ARRAY) || vSetOffset(p, 0)) {
        sCannotSetValueType(sc);
        return;
    }
    p->data.intValue = asAllocate(&sc->arrays, size, length);
    if(p->data.intValue == -1) {
        sError(sc, "out of memory");
    } else if(p->data.intValue == -2) {
        sError(sc, "bad allocation");
    }
}

static void sLength(Script* sc) {
    Value* v = sPeekStack(sc, VT_ARRAY);
    if(v == NULL) {
        return;
    }
    sc->stackIndex--;

    SnuviArray* a = asGet(&sc->arrays, v->data.intValue);
    if(a == NULL) {
        sError(sc, "invalid heap pointer %d", v->data.intValue);
        return;
    }
    sPushInt32(sc, a->length);
}

static void sDereference(Script* sc) {
    int32 address = 0;
    if(sReadInt32(sc, &address)) {
        return;
    }
    Value* v = sPushStack(sc, 1);
    if(vSetType(v, VT_POINTER) || vSetOffset(v, address + sc->stackVarIndex)) {
        sCannotSetValueType(sc);
        return;
    }
    v->data.intValue = -1;
}

static void sGlobalDereference(Script* sc) {
    int32 address = 0;
    if(sReadInt32(sc, &address)) {
        return;
    }
    Value* v = sPushStack(sc, 1);
    if(vSetType(v, VT_POINTER) || vSetOffset(v, address)) {
        sCannotSetValueType(sc);
        return;
    }
    v->data.intValue = -1;
}

static void sDuplicateReference(Script* sc) {
    Value* v = sPeekStack(sc, VT_POINTER);
    if(v != NULL) {
        Value* copy = sPushStack(sc, 1);
        if(copy != NULL) {
            *copy = *v;
        }
    }
}

static void sAddReference(Script* sc) {
    int32 size = 0;
    int32 add = 0;
    if(sReadInt32(sc, &size) || sPopInt32(sc, &add)) {
        return;
    }
    Value* v = sPeekStack(sc, VT_POINTER);
    if(v != NULL) {
        if(vSetOffset(v, vGetOffset(*v) + add * size)) {
            sCannotSetValueType(sc);
        }
    } else {
        sc->error[0] = '\0';
        v = sPeekStack(sc, VT_ARRAY);
        if(vSetType(v, VT_POINTER) ||
           vSetOffset(v, vGetOffset(*v) + add * size)) {
            sCannotSetValueType(sc);
        }
    }
}

static void sPushStructReference(Script* sc) {
    int32 address = 0;
    if(sReadInt32(sc, &address)) {
        return;
    }
    Value* v = sPushStack(sc, 1);
    if(v != NULL) {
        int index = address + sc->stackVarIndex;
        if(index < 0 || index >= SCRIPT_STACK_SIZE) {
            sError(sc, "invalid struct reference address");
            return;
        }
        *v = sc->stack[index];
    }
}

static Value* sLoadFromPointer(Script* sc, Value* p, ValueType wantedType) {
    int32 offset = vGetOffset(*p);
    if(p->data.intValue < 0) {
        if(offset < 0 || offset >= SCRIPT_STACK_SIZE) {
            sError(sc, "invalid offset");
            return NULL;
        }
        Value* v = sc->stack + offset;
        ValueType type = vGetType(*v);
        if(type != wantedType && type != VT_NOT_SET) {
            sError(sc, "pointer did not point to %s but %s", vtGetName(type),
                   vtGetName(type));
            return NULL;
        }
        return v;
    }
    SnuviArray* a = asGet(&sc->arrays, p->data.intValue);
    if(a == NULL) {
        sError(sc, "invalid heap pointer %d", p->data.intValue);
        return NULL;
    }
    if(offset >= a->realLength) {
        sError(sc, "invalid heap pointer offset %d %d", offset, a->realLength);
        return NULL;
    }
    return a->data + offset;
}

SnuviArray* sGetArray(Script* sc) {
    Value* v = sPeekStack(sc, VT_ARRAY);
    if(v == NULL) {
        return NULL;
    }
    sc->stackIndex--;
    return asGet(&sc->arrays, v->data.intValue);
}

Value* sPopStructPointer(Script* sc, ValueType type) {
    Value* v = sPeekStack(sc, VT_POINTER);
    if(v == NULL) {
        return NULL;
    }
    sc->stackIndex--;
    return sLoadFromPointer(sc, v, type);
}

static void sStoreInt32(Script* sc) {
    int32 i = 0;
    if(sPopInt32(sc, &i)) {
        return;
    }
    Value* v = sPeekStack(sc, VT_POINTER);
    if(v == NULL) {
        return;
    }
    sc->stackIndex--;
    v = sLoadFromPointer(sc, v, VT_INT);
    if(vSetType(v, VT_INT)) {
        sCannotSetValueType(sc);
        return;
    }
    v->data.intValue = i;
}

static void sStoreFloat(Script* sc) {
    float f = 0;
    if(sPopFloat(sc, &f)) {
        return;
    }
    Value* v = sPeekStack(sc, VT_POINTER);
    if(v == NULL) {
        return;
    }
    sc->stackIndex--;
    v = sLoadFromPointer(sc, v, VT_FLOAT);
    if(vSetType(v, VT_FLOAT)) {
        sCannotSetValueType(sc);
        return;
    }
    v->data.floatValue = f;
}

static void sStoreArray(Script* sc) {
    Value* array = sPeekStack(sc, VT_ARRAY);
    if(array == NULL) {
        return;
    }
    sc->stackIndex--;
    Value* v = sPeekStack(sc, VT_POINTER);
    if(v == NULL) {
        return;
    }
    sc->stackIndex--;
    v = sLoadFromPointer(sc, v, VT_ARRAY);
    if(v != NULL) {
        *v = *array;
    }
}

static void sLoadInt32(Script* sc) {
    Value* v = sPeekStack(sc, VT_POINTER);
    if(v == NULL) {
        return;
    }
    sc->stackIndex--;
    v = sLoadFromPointer(sc, v, VT_INT);
    if(v != NULL) {
        sPushInt32(sc, v->data.intValue);
    }
}

static void sLoadFloat(Script* sc) {
    Value* v = sPeekStack(sc, VT_POINTER);
    if(v == NULL) {
        return;
    }
    sc->stackIndex--;
    v = sLoadFromPointer(sc, v, VT_FLOAT);
    if(v != NULL) {
        sPushFloat(sc, v->data.floatValue);
    }
}

static void sLoadArray(Script* sc) {
    Value* v = sPeekStack(sc, VT_POINTER);
    if(v == NULL) {
        return;
    }
    sc->stackIndex--;
    v = sLoadFromPointer(sc, v, VT_ARRAY);
    if(v != NULL) {
        Value* array = sPushStack(sc, 1);
        if(array != NULL) {
            *array = *v;
        }
    }
}

static void sEqualArrays(Script* sc, bool wanted) {
    Value* a = sPeekStack(sc, VT_ARRAY);
    if(a == NULL) {
        return;
    }
    sc->stackIndex--;
    Value* b = sPeekStack(sc, VT_ARRAY);
    if(b == NULL) {
        return;
    }
    sc->stackIndex--;
    sPushInt32(sc, (vGetOffset(*a) == vGetOffset(*b) &&
                    a->data.intValue == b->data.intValue) == wanted);
}

static void sCall(Script* sc) {
    int32 function = 0;
    if(sReadInt32(sc, &function)) {
        return;
    }
    if(gfsCall(sc, function)) {
        sError(sc, "invalid function call");
    }
}

static void sPushText(Script* sc) {
    int32 length;
    if(sReadInt32(sc, &length)) {
        return;
    }
    if(length < 0 || length > 65535) {
        sError(sc, "too large string");
        return;
    }
    Value* p = sPushStack(sc, 1);
    if(vSetType(p, VT_ARRAY) || vSetOffset(p, 0)) {
        sCannotSetValueType(sc);
        return;
    }
    p->data.intValue = asAllocate(&sc->arrays, 1, length);
    if(p->data.intValue == -1) {
        sError(sc, "out of memory");
        return;
    } else if(p->data.intValue == -2) {
        sError(sc, "bad allocation");
        return;
    }
    SnuviArray* a = asGet(&sc->arrays, p->data.intValue);
    if(a == NULL) {
        sError(sc, "cannot find text array");
        return;
    }
    for(int i = 0; i < length; i++) {
        sReadInt32(sc, &(a->data[i].data.intValue));
        if(vSetType(a->data + i, VT_INT)) {
            sCannotSetValueType(sc);
            return;
        }
    }
}

static Value* sChangeBase(Script* sc, char* c) {
    if(sRead(sc, c, sizeof(char))) {
        return NULL;
    }
    Value* p = sPeekStack(sc, VT_POINTER);
    if(p == NULL) {
        return NULL;
    }
    sc->stackIndex--;
    return sLoadFromPointer(sc, p, VT_INT);
}

static void sChange(Script* sc) {
    char c;
    Value* v = sChangeBase(sc, &c);
    if(v != NULL) {
        v->data.intValue += c;
    }
}

static void sPushBeforeChange(Script* sc) {
    char c;
    Value* v = sChangeBase(sc, &c);
    if(v != NULL) {
        sPushInt32(sc, v->data.intValue);
        v->data.intValue += c;
    }
}

static void sPushAfterChange(Script* sc) {
    char c;
    Value* v = sChangeBase(sc, &c);
    if(v != NULL) {
        v->data.intValue += c;
        sPushInt32(sc, v->data.intValue);
    }
}

static void sFloatToInt32(Script* sc) {
    Value* v = sPeekStack(sc, VT_FLOAT);
    if(vSetType(v, VT_INT)) {
        sCannotSetValueType(sc);
        return;
    }
    v->data.intValue = (int)v->data.floatValue;
}

static void sInt32ToFloat(Script* sc) {
    Value* v = sPeekStack(sc, VT_INT);
    if(vSetType(v, VT_FLOAT)) {
        sCannotSetValueType(sc);
        return;
    }
    v->data.floatValue = (float)v->data.intValue;
}

#define CASE_NUMBER_OP(name, op)                                               \
    case OP_##name##_INT: NUMBER_OP(int32, Int32, op); return;                 \
    case OP_##name##_FLOAT:                                                    \
        NUMBER_OP(float, Float, op);                                           \
        return;
#define CASE_BOOL_OP(name, op)                                                 \
    case OP_##name##_INT: BOOL_OP(int32, Int32, op); return;                   \
    case OP_##name##_FLOAT:                                                    \
        BOOL_OP(float, Float, op);                                             \
        return;
#define CASE_TYPE(TYPE, Type, type)                                            \
    case OP_RETURN_##TYPE: RETURN(type, Type); return;                         \
    case OP_EQUAL_##TYPE: BOOL_OP(type, Type, ==); return;                     \
    case OP_NOT_EQUAL_##TYPE: BOOL_OP(type, Type, !=); return;

static void sConsumeInstruction(Script* sc) {
    Operation op = sReadOperation(sc);
    switch(op) {
        CASE_NUMBER_OP(ADD, +);
        CASE_NUMBER_OP(SUB, -);
        CASE_NUMBER_OP(MUL, *);
        CASE_BOOL_OP(LESS, <);
        CASE_BOOL_OP(LESS_EQUAL, <=);
        CASE_BOOL_OP(GREATER, >);
        CASE_BOOL_OP(GREATER_EQUAL, >=);
        CASE_TYPE(INT, Int32, int32);
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wfloat-equal"
        CASE_TYPE(FLOAT, Float, float);
        case OP_DIV_FLOAT: DIVISION(float, Float); return;
#pragma GCC diagnostic pop
        case OP_DIV_INT: DIVISION(int32, Int32); return;
        case OP_STORE_INT: sStoreInt32(sc); return;
        case OP_STORE_FLOAT: sStoreFloat(sc); return;
        case OP_LOAD_INT: sLoadInt32(sc); return;
        case OP_LOAD_FLOAT: sLoadFloat(sc); return;
        case OP_PUSH_PRE_CHANGE_INT: sPushAfterChange(sc); return;
        case OP_PUSH_POST_CHANGE_INT: sPushBeforeChange(sc); return;
        case OP_CHANGE_INT: sChange(sc); return;
        case OP_FLOAT_TO_INT: sFloatToInt32(sc); return;
        case OP_INT_TO_FLOAT: sInt32ToFloat(sc); return;
        case OP_BIT_AND_INT: NUMBER_OP(int32, Int32, &); return;
        case OP_BIT_OR_INT: NUMBER_OP(int32, Int32, |); return;
        case OP_BIT_XOR_INT: NUMBER_OP(int32, Int32, ^); return;
        case OP_LEFT_SHIFT_INT: NUMBER_OP(int32, Int32, <<); return;
        case OP_RIGHT_SHIFT_INT: NUMBER_OP(int32, Int32, >>); return;
        case OP_NOTHING: return;
        case OP_PUSH_INT: sPushInt32Value(sc); return;
        case OP_PUSH_FLOAT: sPushFloatValue(sc); return;
        case OP_PUSH_TEXT: sPushText(sc); return;
        case OP_MOD_INT: MODULE(int32, Int32); return;
        case OP_INVERT_SIGN_INT: INVERT_SIGN(int32, Int32); return;
        case OP_INVERT_SIGN_FLOAT: INVERT_SIGN(float, Float); return;
        case OP_NOT: sNot(sc); return;
        case OP_AND: BOOL_OP(int32, Int32, &&); return;
        case OP_OR: BOOL_OP(int32, Int32, ||); return;
        case OP_BIT_NOT_INT: sBitNotInt32(sc); return;
        case OP_LINE: sLine(sc); return;
        case OP_GOTO: sGoTo(sc); return;
        case OP_IF_GOTO: sIfGoTo(sc); return;
        case OP_PEEK_FALSE_GOTO: sPeekFalseGoTo(sc); return;
        case OP_PEEK_TRUE_GOTO: sPeekTrueGoTo(sc); return;
        case OP_GOSUB: sGoSub(sc); return;
        case OP_RETURN: sReturn(sc); return;
        case OP_RETURN_POINTER: sReturnPointer(sc); return;
        case OP_RESERVE: sReserveBytes(sc); return;
        case OP_GRESERVE: sGlobalReserveBytes(sc); return;
        case OP_DEREFERENCE_VAR: sDereference(sc); return;
        case OP_DEREFERENCE_GVAR: sGlobalDereference(sc); return;
        case OP_LOAD_ARRAY: sLoadArray(sc); return;
        case OP_DUPLICATE_REFERENCE: sDuplicateReference(sc); return;
        case OP_ADD_REFERENCE: sAddReference(sc); return;
        case OP_PUSH_STRUCT_REFERENCE: sPushStructReference(sc); return;
        case OP_NEW: sNewArray(sc); return;
        case OP_LENGTH: sLength(sc); return;
        case OP_STORE_ARRAY: sStoreArray(sc); return;
        case OP_EQUAL_POINTER: sEqualArrays(sc, true); return;
        case OP_NOT_EQUAL_POINTER: sEqualArrays(sc, false); return;
        case OP_CALL: sCall(sc); return;
    }
    sError(sc, "unknown operation %d", (int)op);
}

static bool sHasData(Script* sc) {
    return sc->readIndex < sc->code->length;
}

Script* sInit(ByteCode* code) {
    Script* sc = (Script*)malloc(sizeof(Script));
    sc->error[0] = '\0';
    sc->code = code;
    sc->readIndex = 0;
    sc->stackIndex = 0;
    sc->stackVarIndex = 0;
    sc->line = 0;
    asInit(&sc->arrays);
    return sc;
}

void sDelete(Script* sc) {
    bcDelete(sc->code);
    asDelete(&sc->arrays);
    free(sc);
}

void sRun(Script* sc) {
    while(sHasData(sc)) {
        sConsumeInstruction(sc);
        if(sc->error[0] != '\0') {
            return;
        }
    }
}