#include "Code.h"

#include <stdio.h>
#include <string.h>

#include "Code.h"
#include "Constants.h"
#include "Memory.h"

void codeInit(Code* c) {
    *c = (Code){};
    bufferInit(&c->code);
}

void codeDestroy(Code* c) {
    bufferDestroy(&c->code);
    memoryFree(c->stack);
    *c = (Code){};
}

void codeReset(Code* c) {
    bufferReset(&c->code);
}

#define POP_VALUE(name)     \
    Value name;             \
    if(iPopValue(c, &name)) \
    return true

#define INT_VALUE(value) ((Value){.type = VT_INT32, .data = (value)})
#define CSTRING_VALUE(value)                               \
    ((Value){.type = VT_CONSTANT_STRING, .data = (value)})

#define SET_ERROR(format, ...)                \
    snprintf(                                 \
        c->error.text, sizeof(c->error.text), \
        format __VA_OPT__(, ) __VA_ARGS__)

[[nodiscard]] static bool codeReadI32(Code* c, i32* i) {
    return bufferReadI32(&c->code, i);
}

[[nodiscard]] static const char* codeReadConstantString(Code* c) {
    return bufferReadString(&c->code);
}

static void codeSetPosition(Code* c, size_t pos) {
    c->code.readIndex = pos;
}

static i32 codeGetPosition(Code* c) {
    return (i32)c->code.readIndex;
}

static bool iPushValue(Code* c, Value v) {
    while(c->stackIndex >= c->maxStackSize) {
        size_t newSize = c->maxStackSize <= 0 ? 16 : (c->maxStackSize * 5) / 4;
        if(newSize >= MAX_STACK_VALUES) {
            SET_ERROR("Stack overflow");
            return true;
        }
        Value* newValues = memoryAllocate(sizeof(Value) * newSize);
        if(newValues == nullptr) {
            SET_ERROR("Out of memory for stack");
            return true;
        }
        memcpy(newValues, c->stack, sizeof(Value) * c->stackIndex);
        memoryFree(c->stack);
        c->stack = newValues;
        c->maxStackSize = newSize;
    }
    c->stack[c->stackIndex++] = v;
    return false;
}

static bool iPopValue(Code* c, Value* v) {
    if(c->stackIndex <= 0) {
        SET_ERROR("Pop on empty stack");
        return true;
    }
    *v = c->stack[--c->stackIndex];
    return false;
}

static bool iAdd(Code* c) {
    POP_VALUE(a);
    POP_VALUE(b);
    return iPushValue(c, INT_VALUE(a.data + b.data));
}

static bool iPushConstantString(Code* c) {
    const char* s = codeReadConstantString(c);
    i32 address = (i32)((const u8*)s - c->code.data);
    return iPushValue(c, CSTRING_VALUE(address));
}

static bool iPushInt(Code* c) {
    i32 i = 0;
    if(codeReadI32(c, &i)) {
        SET_ERROR("PushInt without value");
        return true;
    }
    return iPushValue(c, INT_VALUE(i));
}

static bool iPrint(Code* c) {
    POP_VALUE(a);
    switch(a.type) {
        case VT_INT32: printf("%d", a.data); break;
        case VT_CONSTANT_STRING: printf("%s", c->code.data + a.data); break;
    }
    return false;
}

static bool iPrintNewline() {
    putchar('\n');
    return false;
}

static bool iJump(Code* c) {
    i32 jumpPos = 0;
    if(codeReadI32(c, &jumpPos)) {
        SET_ERROR("Jump without position");
        return true;
    }
    codeSetPosition(c, (size_t)jumpPos);
    return false;
}

static bool iJumpIf(Code* c) {
    POP_VALUE(a);
    i32 jumpPos = 0;
    if(codeReadI32(c, &jumpPos)) {
        SET_ERROR("JumpIf without position");
        return true;
    }
    if(a.data == 0) {
        codeSetPosition(c, (size_t)jumpPos);
    }
    return false;
}

static bool iJumpSub(Code* c) {
    i32 jumpPos = 0;
    if(codeReadI32(c, &jumpPos)) {
        SET_ERROR("JumpSub without position");
        return true;
    } else if(iPushValue(c, INT_VALUE(codeGetPosition(c)))) {
        return true;
    }
    codeSetPosition(c, (size_t)jumpPos);
    return false;
}

static bool iReturn(Code* c) {
    POP_VALUE(a);
    codeSetPosition(c, (size_t)a.data);
    return false;
}

static bool iReadVariable(Code* c) {
    i32 address = 0;
    if(codeReadI32(c, &address)) {
        SET_ERROR("ReadVariable without address");
        return true;
    } else if((size_t)address >= c->stackIndex) {
        SET_ERROR("ReadVariable with invalid address");
        return true;
    }
    return iPushValue(c, c->stack[address]);
}

static bool iSetVariable(Code* c) {
    i32 address = 0;
    if(codeReadI32(c, &address)) {
        SET_ERROR("SetVariable without address");
        return true;
    } else if((size_t)address >= c->stackIndex) {
        SET_ERROR("SetVariable with invalid address");
        return true;
    }
    POP_VALUE(a);
    c->stack[address] = a;
    return false;
}

static bool iPushStackVariables(Code* c) {
    i32 amount = 0;
    if(codeReadI32(c, &amount)) {
        SET_ERROR("PushStackVariables without amount");
        return true;
    }
    Value v = INT_VALUE(0);
    while(amount > 0) {
        if(iPushValue(c, v)) {
            return true;
        }
        amount--;
    }
    return false;
}

static bool execute(Code* c, Instruction command) {
    switch(command) {
        case ADD: return iAdd(c);
        case PUSH_CONSTANT_STRING: return iPushConstantString(c);
        case PUSH_INT64: return iPushInt(c);
        case PRINT: return iPrint(c);
        case PRINT_NEWLINE: return iPrintNewline();
        case JUMP: return iJump(c);
        case JUMP_ON_0: return iJumpIf(c);
        case JUMP_SUB: return iJumpSub(c);
        case RETURN: return iReturn(c);
        case READ_VARIABLE: return iReadVariable(c);
        case SET_VARIABLE: return iSetVariable(c);
        case PUSH_STACK_VARIABLES: return iPushStackVariables(c);
        case STOP: return true;
    }
    return false;
}

void codeRun(Code* c) {
    while(true) {
        Instruction i = STOP;
        if(bufferReadU8(&c->code, &i) || execute(c, i)) {
            return;
        }
    }
}

bool codeHasRunError(const Code* code) {
    return hasError(&code->error);
}

const char* codeGetRunError(const Code* code) {
    return code->error.text;
}