#include "parser.h"
#include "lexer.h"
#include "scope.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#define PARSER_PANIC(format, ...) {\
    fprintf(\
        stderr,\
        "ccc: parse error: %s: line %lu, column %lu: " format "\n",\
        tok.PATH,\
        tok.LINE,\
        tok.COL __VA_OPT__(,)\
        __VA_ARGS__);\
    exit(1);\
}

static struct token tok;
static struct scope* scope;

static void* protected_alloc(size_t sz) {
    void* ptr = calloc(1, sz);
    if (ptr == NULL) {
        fprintf(stderr, "ccc: out of memory\n");
        exit(1);
    }
    return ptr;
}

static void unexpected_token(enum token_type expected) {
    /* TODO: print what token was expected */
    PARSER_PANIC("unexpected token");
}

/* TODO: reorganize the lexer to make peek cheaper */
static void peek_or_panic() {
    if (!lexer_peek(&tok))
        PARSER_PANIC("unexpected EOF");
}

static void expect(enum token_type expected) {
    if (!lexer_pop(&tok))
        PARSER_PANIC("unexpected EOF");

    if (tok.type != expected) unexpected_token(expected);
}

static void expect_kw(const char* kw) {
    if (!lexer_pop(&tok))
        PARSER_PANIC("unexpected EOF, expected %s", kw);

    if (tok.type != TK_IDENT)
        PARSER_PANIC("unexpected token, expected %s", kw);

    if (strcmp(kw, tok.data.ident) != 0)
        PARSER_PANIC(
            "unexpected identifier %s, expected %s", tok.data.ident, kw);

    /* string won't go in the AST, discard it */
    free(tok.data.ident);
    tok.data.ident = NULL;
}

static void parse_type(struct type_node* p_node) {
    /* TODO: modifiers, void rules, arrays, etc. */
    /* TODO: struct, union, enum */
    expect(TK_IDENT);
    struct type_def type_def;
    if (!scope_get_type(scope, &type_def, tok.data.ident))
        PARSER_PANIC("unknown type name: %s", tok.data.ident);

    p_node->def = type_def;

    peek_or_panic();
    p_node->ptr_level = 0;
    while (tok.type == TK_STAR) {
        expect(TK_STAR);
        p_node->ptr_level++;
        peek_or_panic();
    }
}

static void parse_expr(struct expr_node* p_node);

static void parse_literal(struct expr_node* p_node) {
    peek_or_panic();

    switch (tok.type) {
        case TK_INT_LIT:
            expect(TK_INT_LIT);
            p_node->type = EXPR_INT_LIT;
            p_node->as._int_lit.val = tok.data.int_lit;
            break;
        case TK_CHAR_LIT:
            expect(TK_CHAR_LIT);
            p_node->type = EXPR_CHAR_LIT;
            p_node->as._char_lit.val = tok.data.char_lit;
            break;
        default:
            PARSER_PANIC("invalid literal type");
    }
}

static void parse_var_ref(struct var_ref_node* p_node) {
    expect(TK_IDENT);
    p_node->ident = tok.data.ident;
}

static void expr_to_lval(struct lval_node* l_node, struct expr_node* e_node) {
    switch (e_node->type) {
        case EXPR_VAR_REF:
            *l_node = (struct lval_node) {
                .type = LVAL_VAR_REF,
                .as._var_ref = e_node->as._var_ref,
            };
            return;
        default:
            PARSER_PANIC("expression is not assignable");
    }
}

static void parse_expr_assign(struct expr_node* p_node) {
    expr_to_lval(&p_node->as._assign.lval, p_node);
    p_node->type = EXPR_ASSIGN;
    p_node->as._assign.rval = protected_alloc(sizeof(struct expr_node));

    expect(TK_ASSIGN);
    parse_expr(p_node->as._assign.rval);
}

static void parse_arg_evals(struct expr_node** pp_arg) {
    for (;;) {
        *pp_arg = protected_alloc(sizeof(struct expr_node));
        parse_expr(*pp_arg);
        pp_arg = &((*pp_arg)->next);

        peek_or_panic();
        if (tok.type == TK_RPAREN) break;
        expect(TK_COMMA);
    }
}

static void parse_expr_call(struct expr_node* p_node) {
    switch (p_node->type) {
        case EXPR_VAR_REF:
            struct var_def var_def;
            if (!scope_get_var(scope, &var_def, p_node->as._var_ref.ident))
                PARSER_PANIC(
                    "%s is not a known function", p_node->as._var_ref.ident);

            if (var_def.loc.type != STO_FN)
                PARSER_PANIC("called object is not a function");

            p_node->as._call.called_fn = var_def.loc.decl;
            break;
        default:
            PARSER_PANIC("expression is not callable");
    }

    p_node->type = EXPR_CALL;
    p_node->as._call.args_head = NULL;

    expect(TK_LPAREN);
    peek_or_panic();
    if (tok.type != TK_RPAREN) parse_arg_evals(&p_node->as._call.args_head);
    expect(TK_RPAREN);
}

static void parse_expr(struct expr_node* p_node) {
    peek_or_panic();
    switch (tok.type) {
        case TK_LPAREN:
            expect(TK_LPAREN);
            parse_expr(p_node);
            expect(TK_RPAREN);
            break;
        case TK_INT_LIT:
        case TK_CHAR_LIT:
        case TK_FLOAT_LIT:
        case TK_STR_LIT:
            parse_literal(p_node);
            break;
        case TK_IDENT:
            p_node->type = EXPR_VAR_REF;
            parse_var_ref(&p_node->as._var_ref);
            break;
        default:
            PARSER_PANIC("expected expression");
    }

    peek_or_panic();
    if (tok.type == TK_ASSIGN)
        parse_expr_assign(p_node);
    else if (tok.type == TK_LPAREN)
        parse_expr_call(p_node);
}

static void parse_var_decl(struct var_decl_node* p_node) {
    parse_type(&p_node->type);
    expect(TK_IDENT);
    p_node->ident = tok.data.ident;
}

static void parse_stmt(struct stmt_node* p_node);

static void parse_return(struct return_node* p_node) {
    expect_kw("return");

    peek_or_panic();
    if (tok.type == TK_SEMI) {
        p_node->ret_val = NULL;
        return;
    }

    p_node->ret_val = protected_alloc(sizeof(struct expr_node));
    parse_expr(p_node->ret_val);
}

static void parse_group(struct group_node* p_node) {
    expect(TK_LCURLY);

    struct stmt_node** pp_node = &p_node->body_head;
    for (;;) {
        peek_or_panic();
        if (tok.type == TK_RCURLY) break;

        *pp_node = protected_alloc(sizeof(struct stmt_node));
        parse_stmt(*pp_node);
        pp_node = &((*pp_node)->next);
    }

    expect(TK_RCURLY);
}

static void parse_stmt_assign(struct stmt_node* p_node) {
    peek_or_panic();
    if (tok.type != TK_ASSIGN) return;

    switch (p_node->type) {
        case STMT_VAR_DECL:
            p_node->as._expr.as._assign.lval = (struct lval_node) {
                .type = LVAL_VAR_DECL,
                .as._var_decl = p_node->as._var_decl,
            };
            break;
        default:
            return;
    }

    p_node->type = STMT_EXPR;
    p_node->as._expr.type = EXPR_ASSIGN;
    p_node->as._expr.as._assign.rval =
        protected_alloc(sizeof(struct expr_node));

    expect(TK_ASSIGN);
    parse_expr(p_node->as._expr.as._assign.rval);
}

static void parse_stmt(struct stmt_node* p_node) {
    peek_or_panic();
    switch (tok.type) {
        case TK_SEMI:
            p_node->type = STMT_EMPTY;
            break;
        case TK_LCURLY:
            p_node->type = STMT_GROUP;
            parse_group(&p_node->as._group);
            return;
        case TK_IDENT:
            if (strcmp(tok.data.ident, "return") == 0) {
                p_node->type = STMT_RETURN;
                parse_return(&p_node->as._return);
                break;
            } else if (scope_get_type(scope, NULL, tok.data.ident)) {
                p_node->type = STMT_VAR_DECL;
                parse_var_decl(&p_node->as._var_decl);
                break;
            }
        default:
            p_node->type = STMT_EXPR;
            parse_expr(&p_node->as._expr);
    }

    parse_stmt_assign(p_node);
    expect(TK_SEMI);
}

static void parse_arg_decls(struct var_decl_node** pp_arg) {
    for (;;) {
        *pp_arg = protected_alloc(sizeof(struct var_decl_node));
        parse_var_decl(*pp_arg);
        pp_arg = &((*pp_arg)->next);

        peek_or_panic();
        if (tok.type == TK_RPAREN) break;
        expect(TK_COMMA);
    }
}

static void parse_fn_decl(struct fn_decl_node* p_node) {
    parse_type(&p_node->return_type);

    expect(TK_IDENT);
    p_node->name = tok.data.ident;

    expect(TK_LPAREN);

    peek_or_panic();
    if (tok.type != TK_RPAREN) parse_arg_decls(&p_node->args_head);

    expect(TK_RPAREN);

    parse_group(&p_node->body);

    scope_define_var(scope, (struct var_def) {
        .name = p_node->name,
        .loc = {
            .type = STO_FN,
            .decl = p_node,
        },
    });
}

static bool parse_root(struct root_node* p_node) {
    if (!lexer_peek(&tok)) return false;

    p_node->type = ROOT_FN_DECL;
    parse_fn_decl(&p_node->as._fn_decl);
    return true;
}

struct root_node* parse(const char* path) {
    lexer_load(path);
    scope_push(&scope);
    scope_install_default_types(scope);

    struct root_node* root;
    struct root_node** p_node = &root;

    for (;;) {
        *p_node = protected_alloc(sizeof(struct root_node));
        if (!parse_root(*p_node)) {
            free(*p_node);
            *p_node = NULL;
            break;
        }
        p_node = &((*p_node)->next);
    }

    scope_pop(&scope);
    lexer_close();
    return root;
}