#include <stdbool.h>

enum expr_form {
    expr_ident,
    expr_int_lit,
    expr_bool_lit,
    expr_string_lit,
    expr_list_lit,
    expr_tuple_lit,
    expr_fun_app,
    expr_match,
    expr_let,
};

struct expr;
struct pattern;
struct decl;
struct decl_list;

struct expr_list {
    struct expr *elem;
    struct expr_list *next;
};

struct expr_list_builder {
    struct expr_list *head;
    struct expr_list *last;
};

void expr_list_append(struct expr_list_builder *b, struct expr *elem);
void free_expr_list(struct expr_list *l);

struct func_app {
    struct expr *fun;
    struct expr_list *args;
};

/* List of case alternatives in a match expression */
struct case_list {
    struct pattern *pat;
    struct expr *body;

    struct case_list *next;
};

struct case_list_builder {
    struct case_list *head;
    struct case_list *last;
};

void case_list_append(struct case_list_builder *b, struct pattern *pat, struct expr *body);
void free_case_list(struct case_list *l);

struct match_expr {
    struct expr *cond;
    struct case_list *alts;
};

struct let_expr {
    struct decl_list *local_decls;
    struct expr *body;
};

struct expr {
    enum expr_form form;
    union {
        /* Useful for identifiers, string and integers */
        char *lexeme;
        bool bool_lit;
        struct expr_list *list;
        /* A tuple is represented as a non empty list */
        struct expr_list *tuple;
        struct func_app func_app;
        struct match_expr match;
        struct let_expr let;
    };
};

struct expr *make_ident_expr(char *lexeme);
struct expr *make_int_lit(char *lexeme);
struct expr *make_bool_lit(bool b);
struct expr *make_string_lit(char *lexeme);
struct expr *make_list_lit(struct expr_list *list);
struct expr *make_tuple_lit(struct expr_list *list);
struct expr *make_func_app(struct expr *fun, struct expr_list *args);
struct expr *make_match_expr(struct expr *cond, struct case_list *alts);
struct expr *make_let_expr(struct decl_list *decls, struct expr *body);

void free_expr(struct expr *e);