diff --git a/src/crf_trainer.c b/src/crf_trainer.c
new file mode 100644
index 00000000..9a027966
--- /dev/null
+++ b/src/crf_trainer.c
@@ -0,0 +1,191 @@
+#include "crf_trainer.h"
+
+void crf_trainer_destroy(crf_trainer_t *self) {
+    if (self == NULL) return;
+
+    const char *key;
+    uint32_t id;
+
+    if (self->features != NULL) {
+        kh_foreach(self->features, key, id, {
+            free((char *)key);
+        })
+        kh_destroy(str_uint32, self->features);
+    }
+
+    if (self->prev_tag_features != NULL) {
+        kh_foreach(self->prev_tag_features, key, id, {
+            free((char *)key);
+        })
+        kh_destroy(str_uint32, self->prev_tag_features);
+    }
+
+    if (self->classes != NULL) {
+        kh_foreach(self->classes, key, id, {
+            free((char *)key);
+        })
+        kh_destroy(str_uint32, self->classes);
+    }
+
+    if (self->class_strings != NULL) {
+        cstring_array_destroy(self->class_strings);
+    }
+
+    if (self->context != NULL) {
+        crf_context_destroy(self->context);
+    }
+
+    free(self);
+}
+
+crf_trainer_t *crf_trainer_new(size_t num_classes)  {
+    crf_trainer_t *trainer = malloc(sizeof(crf_trainer_t));
+    if (trainer == NULL) return NULL;
+
+    trainer->num_classes = num_classes;
+
+    trainer->features = kh_init(str_uint32);
+    if (trainer->features == NULL) {
+        goto exit_trainer_created;
+    }
+
+    trainer->prev_tag_features = kh_init(str_uint32);
+    if (trainer->prev_tag_features == NULL) {
+        goto exit_trainer_created;
+    }
+
+    trainer->classes = kh_init(str_uint32);
+    if (trainer->classes == NULL) {
+        goto exit_trainer_created;
+    }
+
+    trainer->class_strings = cstring_array_new();
+    if (trainer->class_strings == NULL) {
+        goto exit_trainer_created;
+    }
+    
+    trainer->context = crf_context_new(CRF_CONTEXT_VITERBI | CRF_CONTEXT_MARGINALS, num_classes, CRF_CONTEXT_DEFAULT_NUM_ITEMS);
+    if (trainer->context == NULL) {
+        goto exit_trainer_created;
+    }
+
+    return trainer;
+
+exit_trainer_created:
+    crf_trainer_destroy(trainer);
+    return NULL;
+
+}
+
+bool crf_trainer_get_class_id_exists(crf_trainer_t *self, char *class_name, uint32_t *class_id, bool add_if_missing, bool *exists) {
+    khiter_t k;
+
+    if (class_name == NULL) {
+        log_error("class_name was NULL\n");
+        return false;
+    }
+
+    khash_t(str_uint32) *classes = self->classes;
+
+    k = kh_get(str_uint32, classes, class_name);
+    if (k != kh_end(classes)) {
+        *class_id = kh_value(classes, k);
+        *exists = true;
+        return true;
+    } else if (add_if_missing) {
+        uint32_t new_id = (uint32_t)kh_size(classes);
+        int ret;
+        char *key = strdup(class_name);
+        if (key == NULL) {
+            return false;
+        }
+        k = kh_put(str_uint32, classes, key, &ret);
+        if (ret < 0) {
+            return false;
+        }
+        kh_value(classes, k) = new_id;
+        *class_id = new_id;
+        *exists = false;
+        cstring_array_add_string(self->class_strings, class_name);
+        return true;
+    }
+    return false;
+}
+
+inline bool crf_trainer_get_class_id(crf_trainer_t *self, char *class_name, uint32_t *class_id, bool add_if_missing) {
+    bool exists;
+    return crf_trainer_get_class_id_exists(self, class_name, class_id, add_if_missing, &exists);
+}
+
+crf_trainer_t *crf_trainer_new_classes(cstring_array *classes)  {
+    if (classes == NULL) return NULL;
+    size_t num_classes = cstring_array_num_strings(classes);
+    crf_trainer_t *trainer = crf_trainer_new(num_classes);
+    if (trainer == NULL) return NULL;
+
+    size_t i;
+    char *class_name;
+    uint32_t class_id;
+    bool add_if_missing = true;
+
+    cstring_array_foreach(classes, i, class_name, {
+        bool exists;
+        if (!crf_trainer_get_class_id_exists(trainer, class_name, &class_id, add_if_missing, &exists)) {
+            crf_trainer_destroy(trainer);
+            return NULL;
+        }
+
+        if (exists) {
+            log_error("Duplicate class: %s\n", class_name);
+            crf_trainer_destroy(trainer);
+            return NULL;
+        }
+    })
+    return trainer;
+}
+
+bool crf_trainer_hash_to_id(khash_t(str_uint32) *features, char *feature, uint32_t *feature_id, bool *exists) {
+    if (feature == NULL) {
+        log_error("feature was NULL\n");
+        return false;
+    }
+
+    if (features == NULL) {
+        log_error("features hashtable was NULL\n");
+        return false;
+    }
+
+    if (str_uint32_hash_to_id_exists(features, feature, feature_id, exists)) {
+        return true;
+    }
+
+    return false;
+}
+
+
+inline bool crf_trainer_hash_feature_to_id_exists(crf_trainer_t *self, char *feature, uint32_t *feature_id, bool *exists) {
+    return crf_trainer_hash_to_id(self->features, feature, feature_id, exists);
+}
+
+inline bool crf_trainer_hash_feature_to_id(crf_trainer_t *self, char *feature, uint32_t *feature_id) {
+    bool exists;
+    return crf_trainer_hash_feature_to_id_exists(self, feature, feature_id, &exists);
+}
+
+
+inline bool crf_trainer_hash_prev_tag_feature_to_id_exists(crf_trainer_t *self, char *feature, uint32_t *feature_id, bool *exists) {
+    return crf_trainer_hash_to_id(self->prev_tag_features, feature, feature_id, exists);
+}
+
+inline bool crf_trainer_hash_prev_tag_feature_to_id(crf_trainer_t *self, char *feature, uint32_t *feature_id) {
+    bool exists;
+    return crf_trainer_hash_feature_to_id_exists(self, feature, feature_id, &exists);
+}
+
+inline bool crf_trainer_get_feature_id(crf_trainer_t *self, char *feature, uint32_t *feature_id) {
+    return str_uint32_hash_get(self->features, feature, feature_id);
+}
+
+inline bool crf_trainer_get_prev_tag_feature_id(crf_trainer_t *self, char *feature, uint32_t *feature_id) {
+    return str_uint32_hash_get(self->prev_tag_features, feature, feature_id);
+}
diff --git a/src/crf_trainer.h b/src/crf_trainer.h
new file mode 100644
index 00000000..498aad8e
--- /dev/null
+++ b/src/crf_trainer.h
@@ -0,0 +1,38 @@
+#ifndef CRF_TRAINER_H
+#define CRF_TRAINER_H
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "collections.h"
+#include "crf_context.h"
+#include "string_utils.h"
+#include "tokens.h"
+#include "trie.h"
+#include "trie_utils.h"
+
+typedef struct crf_trainer {
+    uint32_t num_classes;
+    khash_t(str_uint32) *features;
+    khash_t(str_uint32) *prev_tag_features;
+    khash_t(str_uint32) *classes;
+    cstring_array *class_strings;
+    crf_context_t *context;
+} crf_trainer_t;
+
+
+crf_trainer_t *crf_trainer_new(size_t num_classes);
+void crf_trainer_destroy(crf_trainer_t *self);
+
+bool crf_trainer_get_class_id(crf_trainer_t *self, char *class_name, uint32_t *class_id, bool add_if_missing);
+bool crf_trainer_hash_feature_to_id(crf_trainer_t *self, char *feature, uint32_t *feature_id);
+bool crf_trainer_hash_feature_to_id_exists(crf_trainer_t *self, char *feature, uint32_t *feature_id, bool *exists);
+
+bool crf_trainer_hash_prev_tag_feature_to_id(crf_trainer_t *self, char *feature, uint32_t *feature_id);
+bool crf_trainer_hash_prev_tag_feature_to_id_exists(crf_trainer_t *self, char *feature, uint32_t *feature_id, bool *exists);
+
+
+bool crf_trainer_get_feature_id(crf_trainer_t *self, char *feature, uint32_t *feature_id);
+bool crf_trainer_get_prev_tag_feature_id(crf_trainer_t *self, char *feature, uint32_t *feature_id);
+
+#endif
\ No newline at end of file