#include "type_checker.h"
#include "scope.h"
#include <stdio.h>
#include <stdlib.h>

#define TYPE_PANIC(format, ...) {\
    fprintf(\
        stderr,\
        "ccc: type error: " format "\n" __VA_OPT__(,)\
        __VA_ARGS__);\
    exit(1);\
}

static struct ast* ast_ref;
static struct scope* scope;

static void type_check_expr(struct expr_node* node);
static void type_check_stmt(struct stmt_node* node);
static void type_check_group(struct group_node* node);

static const char* get_type_name(const struct type* type) {
    switch (type->type) {
        case TP_DATA:
            return type->data.data_type->name;
        case TP_PTR:
            /* TODO: this is a stub */
            return type->pointer.data_type->name;
    }
    TYPE_PANIC("unhandled type of type case");
}

static void assert_cast_compatible(
    const struct type* lval_type,
    const struct type* rval_type
) {
    /* TODO: impl */
    /* TODO: we should also insert cast nodes eventually */
    if (false) {
        TYPE_PANIC(
            "cannot assign value of type '%s' to '%s'",
            get_type_name(lval_type),
            get_type_name(rval_type));
    }
}

static void enter_scope(struct scope* child_scope) {
    if (child_scope == NULL ||
            child_scope->next_out != scope)
        TYPE_PANIC("enter_scope: scopes are misaligned");

    scope = child_scope;
}

static void exit_scope(struct scope* child_scope) {
    if (child_scope != scope || child_scope->next_out == NULL)
        TYPE_PANIC("exit_scope: scopes are misaligned");

    scope = child_scope->next_out;
}

static struct type* allocate_data_type(
    const struct data_type* data_type,
    bool is_unsigned
) {
    if (is_unsigned && data_type->is_floating)
        TYPE_PANIC("floating type '%s' cannot be unsigned", data_type->name);

    struct type* type = ccc_alloc(sizeof(struct type));
    type->type = TP_DATA;
    type->data.data_type = data_type;
    type->data.is_signed = !is_unsigned;
    return type;
}

static struct type* allocate_pointer_type(
    const struct data_type* data_type,
    integral_t ptr_level
) {
    struct type* type = ccc_alloc(sizeof(struct type));
    type->type = TP_PTR;
    type->pointer.data_type = data_type;
    type->pointer.ptr_level = ptr_level;
    return type;
}

static struct type* copy_type(const struct type* source_type) {
    struct type* type = ccc_alloc(sizeof(struct type));
    *type = *source_type;
    return type;
}

static struct type* resolve_var_ref(struct var_ref_node* node) {
    if (node->def_ref->type == NULL)
        TYPE_PANIC("variable '%s' has undefined type.", node->def_ref->name);
    return copy_type(node->def_ref->type);
}

static void type_check_var_decl(struct var_decl_node* node) {
    node->def_ref->type = &node->type;
    if (node->initial_value != NULL) {
        type_check_expr(node->initial_value);
        assert_cast_compatible(&node->type, node->initial_value->resolved_type);
    }
}

static struct type* resolve_assign(struct assign_node* node) {
    switch (node->lval->type) {
        case EXPR_VAR_REF:
            break;
        default:
            TYPE_PANIC("expression is not assignable");
    }

    type_check_expr(node->lval);
    type_check_expr(node->rval);
    const struct type* lval_type = node->lval->resolved_type;
    const struct type* rval_type = node->rval->resolved_type;

    assert_cast_compatible(lval_type, rval_type);
    return copy_type(lval_type);
}

static struct type* resolve_call(struct call_node* node) {
    struct decl_list_node* arg_decl = node->called_fn_ref->args;
    struct expr_list_node* arg_eval = node->args;
    while (arg_decl != NULL && arg_eval != NULL) {
        if (arg_decl->decl->initial_value != NULL)
            TYPE_PANIC("C does not support default arguments");

        type_check_var_decl(arg_decl->decl);
        const struct type* decl_type =
            arg_decl->decl->def_ref->type;
        type_check_expr(arg_eval->expr);
        const struct type* eval_type = arg_eval->expr->resolved_type;
        assert_cast_compatible(decl_type, eval_type);

        arg_decl = arg_decl->next;
        arg_eval = arg_eval->next;
    }
    if (arg_decl != NULL || arg_eval != NULL)
        TYPE_PANIC(
            "mismatched argument count in call to '%s'",
            node->called_fn_ref->name);

    return copy_type(&node->called_fn_ref->return_type);
}

static struct type* resolve_unary(struct unary_node* node) {
    type_check_expr(node->expr);
    /* TODO: delegate by individual operation to prohibit shit like -"yes" */
    return copy_type(node->expr->resolved_type);
}

static struct type* resolve_binary(struct binary_node* node) {
    /* TODO: math rules and such lol */
    type_check_expr(node->lhs);
    type_check_expr(node->rhs);
    assert_cast_compatible(node->lhs->resolved_type, node->rhs->resolved_type);
    return copy_type(node->lhs->resolved_type);
}

static void type_check_expr(struct expr_node* node) {
    switch (node->type) {
        case EXPR_INT_LIT:
            node->resolved_type = allocate_data_type(integral_type, false);
            break;
        case EXPR_FLOAT_LIT:
            node->resolved_type = allocate_data_type(floating_type, false);
            break;
        case EXPR_CHAR_LIT:
            node->resolved_type = allocate_data_type(character_type, false);
            break;
        case EXPR_STR_LIT:
            node->resolved_type = allocate_pointer_type(character_type, 1);
            break;
        case EXPR_VAR_REF:
            node->resolved_type = resolve_var_ref(&node->inner.var_ref);
            break;
        case EXPR_ASSIGN:
            node->resolved_type = resolve_assign(&node->inner.assign);
            break;
        case EXPR_CALL:
            node->resolved_type = resolve_call(&node->inner.call);
            break;
        case EXPR_UNARY:
            node->resolved_type = resolve_unary(&node->inner.unary);
            break;
        case EXPR_BINARY:
            node->resolved_type = resolve_binary(&node->inner.binary);
            break;
    }
}

static void type_check_return(struct return_node* node) {
    if (node->ret_val != NULL) type_check_expr(node->ret_val);
}

static void type_check_if(struct if_node* node) {
    enter_scope(node->scope);

    type_check_expr(node->cond);
    type_check_stmt(node->true_branch);
    if (node->false_branch != NULL) type_check_stmt(node->false_branch);

    exit_scope(node->scope);
}

static void type_check_expr_list(struct expr_list_node* node) {
    for (; node != NULL; node = node->next) type_check_expr(node->expr);
}

static void type_check_loop_init(struct loop_init_node* node) {
    switch (node->type) {
        case INIT_EXPR_LIST:
            type_check_expr_list(node->expr_list);
            break;
        case INIT_DECL:
            type_check_var_decl(node->decl);
            break;
    }
}

static void type_check_loop(struct loop_node* node) {
    enter_scope(node->scope);

    if (node->init != NULL) type_check_loop_init(node->init);
    if (node->cond != NULL) type_check_expr(node->cond);
    if (node->incr != NULL) type_check_expr(node->incr);
    type_check_stmt(node->body);

    exit_scope(node->scope);
}

static void type_check_stmt(struct stmt_node* node) {
    switch (node->type) {
        case STMT_EMPTY:
            break;
        case STMT_EXPR:
            type_check_expr(&node->inner.expr);
            break;
        case STMT_VAR_DECL:
            type_check_var_decl(&node->inner.var_decl);
            break;
        case STMT_RETURN:
            type_check_return(&node->inner.return_);
            break;
        case STMT_GROUP:
            type_check_group(&node->inner.group);
            break;
        case STMT_IF:
            type_check_if(&node->inner.if_);
            break;
        case STMT_LOOP:
            type_check_loop(&node->inner.loop);
            break;
    }
}

static void type_check_group(struct group_node* node) {
    enter_scope(node->scope);

    struct stmt_node* stmt = node->head;
    while (stmt != NULL) {
        type_check_stmt(stmt);
        stmt = stmt->next;
    }

    exit_scope(node->scope);
}

static void type_check_fn_decl(struct fn_decl_node* node) {
    enter_scope(node->scope);

    for (struct decl_list_node* arg_decl = node->args;
            arg_decl != NULL;
            arg_decl = arg_decl->next)
        type_check_var_decl(arg_decl->decl);

    type_check_group(&node->body);

    exit_scope(node->scope);
}

static void type_check_root(struct root_node* node) {
    switch (node->type) {
        case ROOT_FN_DECL:
            type_check_fn_decl(&node->inner.fn_decl);
            break;
    }
}

void type_check(struct ast* ast) {
    ast_ref = ast;
    scope = ast->root_scope;

    struct root_node* node = ast->root_node;
    while (node != NULL) {
        type_check_root(node);
        node = node->next;
    }

    ast_ref = NULL;
    scope = NULL;
}