typedef enum {
    TOKEN_WORD,
    TOKEN_PIPE,
    TOKEN_REDIRECT_IN,
    TOKEN_REDIRECT_OUT,
    TOKEN_REDIRECT_APPEND,
    TOKEN_HEREDOC,
    TOKEN_EOF
} token_type_t;

typedef struct s_token {
    token_type_t type;
    char *value;
    struct s_token *next;
} t_token;

t_token *tokenize(const char *input) {
    t_token *head = NULL;
    t_token *current = NULL;

    // Implementation details...
}