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

#include <llvm-c/Core.h>
#include <llvm-c/Analysis.h>
#include <llvm-c/BitWriter.h>

#include "y.tab.h"
#include "ast.h"
#include "stack.h"

extern FILE *yyin;
Stack *stack;
Node *rootNode;

typedef struct VariableMapValue
{
    char *name;
    LLVMValueRef variable;
} VariableMapValue;

VariableMapValue *namedVariables;
uint32_t namedVariableCount;

static LLVMValueRef CompileExpression(
    LLVMModuleRef module,
    LLVMBuilderRef builder,
    LLVMValueRef function,
    Node *binaryExpression
);

static void AddNamedVariable(char *name, LLVMValueRef variable)
{
    VariableMapValue mapValue;
    mapValue.name = name;
    mapValue.variable = variable;

    namedVariables = realloc(namedVariables, namedVariableCount + 1);
    namedVariables[namedVariableCount] = mapValue;

    namedVariableCount += 1;
}

static LLVMValueRef FindVariableByName(char *name)
{
    uint32_t i;

    for (i = 0; i < namedVariableCount; i += 1)
    {
        if (strcmp(namedVariables[i].name, name) == 0)
        {
            return namedVariables[i].variable;
        }
    }

    return NULL;
}

static LLVMTypeRef WraithTypeToLLVMType(PrimitiveType type)
{
    switch (type)
    {
        case Int:
            return LLVMInt64Type();

        case UInt:
            return LLVMInt64Type();
    }

    return NULL;
}

static LLVMValueRef CompileNumber(
    LLVMModuleRef module,
    LLVMBuilderRef builder,
    LLVMValueRef function,
    Node *numberExpression
)
{
    return LLVMConstInt(LLVMInt64Type(), numberExpression->value.number, 0);
}

static LLVMValueRef CompileBinaryExpression(
    LLVMModuleRef module,
    LLVMBuilderRef builder,
    LLVMValueRef function,
    Node *binaryExpression
) {
    LLVMValueRef left = CompileExpression(module, builder, function, binaryExpression->children[0]);
    LLVMValueRef right = CompileExpression(module, builder, function, binaryExpression->children[1]);

    switch (binaryExpression->operator.binaryOperator)
    {
        case Add:
            return LLVMBuildAdd(builder, left, right, "tmp");
    }

    return NULL;
}

static LLVMValueRef CompileExpression(
    LLVMModuleRef module,
    LLVMBuilderRef builder,
    LLVMValueRef function,
    Node *expression
) {
    switch (expression->syntaxKind)
    {
        case BinaryExpression:
            return CompileBinaryExpression(module, builder, function, expression);

        case Identifier:
            return FindVariableByName(expression->value.string);

        case Number:
            return CompileNumber(module, builder, function, expression);
    }

    printf("Error: expected expression\n");
    return NULL;
}

static void CompileReturn(LLVMModuleRef module, LLVMBuilderRef builder, LLVMValueRef function, Node *returnStatemement)
{
    LLVMBuildRet(builder, CompileExpression(module, builder, function, returnStatemement->children[0]));
}

static void CompileStatement(LLVMModuleRef module, LLVMBuilderRef builder, LLVMValueRef function, Node *statement)
{
    switch (statement->syntaxKind)
    {
        case Return:
            CompileReturn(module, builder, function, statement);
            break;
    }
}

static void CompileFunction(LLVMModuleRef module, Node *functionDeclaration)
{
    uint32_t i;
    Node *functionSignature = functionDeclaration->children[0];
    Node *functionBody = functionDeclaration->children[1];
    LLVMTypeRef paramTypes[functionSignature->children[2]->childCount];

    for (i = 0; i < functionSignature->children[2]->childCount; i += 1)
    {
        paramTypes[i] = WraithTypeToLLVMType(functionSignature->children[2]->children[i]->children[0]->type);
    }

    LLVMTypeRef functionType = LLVMFunctionType(WraithTypeToLLVMType(functionSignature->children[1]->type), paramTypes, functionSignature->children[2]->childCount, 0);

    LLVMValueRef function = LLVMAddFunction(module, functionSignature->children[0]->value.string, functionType);

    for (i = 0; i < functionSignature->children[2]->childCount; i += 1)
    {
        LLVMValueRef argument = LLVMGetParam(function, i);
        AddNamedVariable(functionSignature->children[2]->children[i]->children[1]->value.string, argument);
    }

    LLVMBasicBlockRef entry = LLVMAppendBasicBlock(function, "entry");

    LLVMBuilderRef builder = LLVMCreateBuilder();
    LLVMPositionBuilderAtEnd(builder, entry);

    for (i = 0; i < functionBody->childCount; i += 1)
    {
        CompileStatement(module, builder, function, functionBody->children[i]);
    }
}

static void Compile(LLVMModuleRef module, Node *node)
{
    uint32_t i;

    switch (node->syntaxKind)
    {
        case FunctionDeclaration:
            CompileFunction(module, node);
            break;
    }

    for (i = 0; i < node->childCount; i += 1)
    {
        Compile(module, node->children[i]);
    }
}

int main(int argc, char *argv[])
{
    if (argc < 2)
    {
        printf("Please provide a file.\n");
        return 1;
    }

    namedVariables = NULL;
    namedVariableCount = 0;

    stack = CreateStack();

    FILE *fp = fopen(argv[1], "r");
    yyin = fp;
    yyparse(fp, stack);
    fclose(fp);

    PrintTree(rootNode, 0);

    LLVMModuleRef module = LLVMModuleCreateWithName("my_module");

    Compile(module, rootNode);

    char *error = NULL;
    LLVMVerifyModule(module, LLVMAbortProcessAction, &error);
    LLVMDisposeMessage(error);

    if (LLVMWriteBitcodeToFile(module, "test.bc") != 0) {
        fprintf(stderr, "error writing bitcode to file\n");
    }

    return 0;
}