diff --git a/Makefile b/Makefile
index 41a4190..16bdfcc 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 SRC := $(wildcard src/*.c)
 CFLAGS := -lcrypto -lm -lz
 
-DEBUG = false
+DEBUG ?= false
 ifeq ($(DEBUG), true)
 	DEBUG_FLAG = -DDEBUG -ggdb
 endif
diff --git a/src/cgit.c b/src/cgit.c
deleted file mode 100644
index 6cd387d..0000000
--- a/src/cgit.c
+++ /dev/null
@@ -1,12 +0,0 @@
-// Requirements
-// commit
-// branching
-// revert
-// pull/push
-
-#include <stdio.h>
-
-int main(int argc, char** argv) {
-    printf("%s", "Hello World!\n");
-    return 0;
-}
\ No newline at end of file
diff --git a/src/commit.c b/src/commit.c
new file mode 100644
index 0000000..c33c812
--- /dev/null
+++ b/src/commit.c
@@ -0,0 +1,148 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "commit.h"
+#include "fs.h"
+#include "includes.h"
+#include "objects.h"
+#include "tree.h"
+#include "types.h"
+
+int commit_from_object(struct commit *commit, struct object *object)
+{
+    char tmp[object->size + 1];
+    memcpy(tmp, object->content, object->size);
+    tmp[object->size] = '\0';
+    char *current_line = strtok(tmp, "\n");
+    commit->tree = malloc(strlen(current_line) + 1);
+    sprintf(commit->tree, "%s", current_line);
+
+    current_line = strtok(NULL, "\n");
+    commit->parent = malloc(strlen(current_line) + 1);
+    sprintf(commit->parent, "%s", current_line);
+
+    current_line = strtok(NULL, "\n");
+    commit->author = malloc(strlen(current_line) + 1);
+    sprintf(commit->author, "%s", current_line);
+    return 0;
+}
+
+int commit_to_object(struct commit *commit, struct object *object)
+{
+    object->object_type = COMMIT;
+    object->size = strlen(commit->tree) + 2;
+    object->content = malloc(object->size);
+    sprintf(object->content, "%s\n", commit->tree);
+
+    object->size += strlen(commit->parent) + 1;
+    object->content = realloc(object->content, object->size);
+    strncat(object->content, commit->parent, strlen(commit->parent));
+    strcat(object->content, "\n");
+
+    object->size += strlen(commit->author);
+    object->content = realloc(object->content, object->size);
+    strncat(object->content, commit->author, strlen(commit->author));
+
+    object->size --;
+}
+
+void free_commit(struct commit *commit)
+{
+    if (commit->author != NULL)
+        free(commit->author);
+    
+    if (commit->parent != NULL)
+        free(commit->parent);
+
+    if (commit->tree != NULL)
+        free(commit->tree);
+}
+
+int commit()
+{
+    struct tree index = {0};
+    load_index(&index);
+
+    struct object last_commit = {0};
+    struct commit commit = {0};
+    char last_commit_checksum[DIGEST_LENGTH * 2 + 1] = {0};
+    struct tree commit_tree = {0};
+    get_last_commit(&last_commit);
+    if (last_commit.size != 0) {
+        hash_object(&last_commit, last_commit_checksum);
+        commit_from_object(&commit, &last_commit);
+
+        struct object last_commit_tree = {0};
+        read_object(commit.tree, &last_commit_tree);
+        get_tree(last_commit_tree.content, &commit_tree);
+        free_object(&last_commit_tree);
+    }
+    free_object(&last_commit);
+
+    struct entry *current = index.first_entry;
+    while(current != NULL)
+    {
+        size_t entry_size = DIGEST_LENGTH * 2 + 2 + strlen(current->filename);
+        char tmp[entry_size + 1];
+        sprintf(tmp, "%s %s\n", current->checksum, current->filename);
+        
+        struct object object = {0};
+        blob_from_file(current->filename, &object);
+
+        add_object_to_tree(&commit_tree, current->filename, &object);
+
+        free_object(&object);
+        current = current->next;
+    }
+
+    if (commit.author == NULL)
+    {
+        char* author = "Antonin";
+        commit.author = malloc(strlen(author) + 1);
+        sprintf(commit.author, "%s", author);
+    }
+
+
+    commit.parent = realloc(commit.parent, DIGEST_LENGTH * 2 + 1);
+    if (last_commit.size == 0)
+    {
+        sprintf(commit.parent, "%s", " ");
+    } else
+    {
+        sprintf(commit.parent, "%s", last_commit_checksum);
+    }
+
+    struct object commit_tree_obj = {0};
+    tree_to_object(&commit_tree, &commit_tree_obj);
+    char *commit_tree_checksum = malloc(DIGEST_LENGTH * 2 + 1);
+    hash_object(&commit_tree_obj, commit_tree_checksum);
+    write_object(&commit_tree_obj);
+
+    if(commit.tree != NULL)
+    {
+        free(commit.tree);
+    }
+    commit.tree = commit_tree_checksum;
+
+    debug_print("Author: %s", commit.author);
+    debug_print("Parent: %s", commit.parent);
+    debug_print("Tree: %s", commit.tree);
+
+    struct object commit_obj = {0};
+    commit_to_object(&commit, &commit_obj);
+    write_object(&commit_obj);
+    char commit_checksum[DIGEST_LENGTH * 2 + 1];
+    hash_object(&commit_obj, commit_checksum);
+
+    update_head(commit_checksum);
+
+    free_commit(&commit);
+    free_object(&commit_obj);
+    free_tree(&commit_tree);
+    free_object(&commit_tree_obj);
+    free_tree(&index);
+    
+    memset(&index, 0, sizeof(struct tree));
+    save_index(&index);
+}
\ No newline at end of file
diff --git a/src/commit.h b/src/commit.h
new file mode 100644
index 0000000..aa1fa46
--- /dev/null
+++ b/src/commit.h
@@ -0,0 +1,6 @@
+#ifndef COMMIT_H
+#define COMMIT_H 1
+
+int commit();
+
+#endif // COMMIT_H
\ No newline at end of file
diff --git a/src/fs.c b/src/fs.c
index a7f83c0..325a1bf 100644
--- a/src/fs.c
+++ b/src/fs.c
@@ -11,7 +11,7 @@
 
 #include "fs.h"
 #include "includes.h"
-#include "index.h"
+#include "tree.h"
 #include "objects.h"
 #include "utils.h"
 
@@ -27,99 +27,41 @@ int index_exist()
     return stat(INDEX_FILE, &buffer) == 0;
 }
 
-void dump_index(struct index *index)
+int heads_dir_exist()
 {
-    printf("index:\n");
-    printf("\tentries_size: %ld\n", index->entries_size);
-    printf("\tentries:\n");
-    struct entry *current = index->first_entry;
-    for(int i = 0; i < index->entries_size; i ++)
-    {
-        printf("\t\tfilename: %s, checksum: %s\n", current->filename, current->checksum);
-        current = current->next;
-    }
+    struct stat buffer;
+    return stat(HEADS_DIR, &buffer) == 0; 
 }
 
-int load_index(struct index *index)
+int head_file_exist(size_t *head_size)
 {
-    if(!local_repo_exist() || !index_exist())
-    {
-        return REPO_NOT_INITIALIZED;
-    }
-
-    FILE* index_file = fopen(INDEX_FILE, "r");
     struct stat buffer;
-    stat(INDEX_FILE, &buffer);
+    int result = stat(HEAD_FILE, &buffer) == 0;
+    *head_size = buffer.st_size;
+    return result;
+}
 
-    char* file_content = calloc(sizeof(char), buffer.st_size + 1);
-    fread(file_content, buffer.st_size, 1, index_file);
-    fclose(index_file);
-
-    char* current_line;
-    current_line = strtok(file_content, "\n");
-    index->entries_size = strtol(current_line, NULL, 10);
-    
-    for(int i = 0; i < index->entries_size; i++)
-    {
-        current_line = strtok(NULL, "\n");
-        int j = 0;
-        while(current_line[j] != ' ')
-        {
-            j++;
-        }
-
-        char* checksum = calloc(sizeof(char), j + 1);
-        char* filename = calloc(sizeof(char), strlen(current_line) - j);
-        strncat(checksum, current_line, j);
-        strncat(filename, current_line + j + 1, strlen(current_line) - j);
-
-        struct entry *entry = malloc(sizeof(struct entry));
-        entry->checksum = checksum;
-        entry->filename = filename;
-        entry->next = NULL;
-
-        if(i == 0)
-        {
-            index->first_entry = entry;
-        } else 
-        {
-            entry->previous = index->last_entry;
-            index->last_entry->next = entry;
-        }
-        index->last_entry = entry;
-        debug_print("checksum: %s, filename: %s", entry->checksum, entry->filename);
+int blob_from_file(char *filename, struct object *object)
+{
+    FILE* file = fopen(filename, "r");
+    if (file == NULL) {
+        error_print("File %s not found", filename);
+        return FILE_NOT_FOUND;
     }
 
-    free(file_content);
+    struct stat file_info;
+    if (stat(filename, &file_info) != 0)
+        return -1;
+    
+    object->object_type = str_to_object_type("blob");
+    object->size = file_info.st_size;
+    object->content = realloc(object->content, object->size);
+    fread(object->content, 1, object->size, file);
+    fclose(file);
 
     return FS_OK;
 }
 
-int save_index(struct index *index)
-{
-    if(!local_repo_exist())
-    {
-        return REPO_NOT_INITIALIZED;
-    }
-
-    FILE *index_file = fopen(INDEX_FILE, "w");
-    if(index_exist == NULL)
-    {
-        return FS_ERROR;
-    }
-
-    fprintf(index_file, "%li\n", index->entries_size);
-
-    struct entry *current = index->first_entry;
-    for(int i = 0; i < index->entries_size; i++)
-    {
-        fprintf(index_file, "%s %s\n", current->checksum, current->filename);
-        current = current->next;
-    }
-
-    fclose(index_file);
-}
-
 int write_object(struct object *obj)
 {
     if(!local_repo_exist())
@@ -129,12 +71,12 @@ int write_object(struct object *obj)
     int result = FS_OK;
 
     struct stat buffer;
-    if (stat(OBJECTS_REPO, &buffer) != 0)
+    if (stat(OBJECTS_DIR, &buffer) != 0)
     {
-        mkdir(OBJECTS_REPO, DEFAULT_DIR_MODE);
+        mkdir(OBJECTS_DIR, DEFAULT_DIR_MODE);
     }
     
-    DIR *objects_dir = opendir(OBJECTS_REPO);
+    DIR *objects_dir = opendir(OBJECTS_DIR);
     int objects_dir_fd = dirfd(objects_dir);
 
     char checksum[DIGEST_LENGTH * 2];
@@ -178,15 +120,17 @@ int read_object(char *checksum, struct object *obj)
     int result = FS_OK;
 
     struct stat buffer;
-    if (stat(OBJECTS_REPO, &buffer) != 0)
+    if (stat(OBJECTS_DIR, &buffer) != 0)
     {
         error_print("Object dir does not exist");
         return OBJECT_DOES_NOT_EXIST;
     }
 
-    DIR *objects_dir = opendir(OBJECTS_REPO);
+    DIR *objects_dir = opendir(OBJECTS_DIR);
     int objects_dir_fd = dirfd(objects_dir);
 
+    fstatat(objects_dir_fd, checksum, &buffer, 0);
+    char file_content[buffer.st_size];
     int save_file_fd = openat(objects_dir_fd, checksum, O_RDONLY, DEFAULT_FILE_MODE);    
     if (save_file_fd == -1)
     {
@@ -195,55 +139,141 @@ int read_object(char *checksum, struct object *obj)
             error_print("Object %s does not exist", checksum);
             defer(OBJECT_DOES_NOT_EXIST);
         }
+        error_print("Cannot open file %s", checksum);
         defer(FS_ERROR);
     }
-    fstatat(objects_dir_fd, checksum, &buffer, 0);
-    char* file_content = malloc(buffer.st_size);
 
     FILE *save_file = fdopen(save_file_fd, "r");
     fread(file_content, 1, buffer.st_size, save_file);
     fclose(save_file);
 
-    int res = uncompress_object(obj, file_content, buffer.st_size);
-    if(res != Z_OK)
-    {
-        defer(COMPRESSION_ERROR);
-    }
-    
-    free(file_content);
+    result = uncompress_object(obj, file_content, buffer.st_size);
 
 defer:
     closedir(objects_dir);
     return result;
 }
 
-int main(void)
+int load_tree(char* checksum, struct tree *tree)
 {
-    struct index index = {0};
-    load_index(&index);
+    struct object object;
+    int res = read_object(checksum, &object);
+    if (res != FS_OK)
+        return res;
 
-    // struct object obj = {0};
-    // obj.content = "Hello, world!\n";
-    // obj.size = strlen(obj.content);
-    // obj.object_type = "blob";
+    if (object.object_type != TREE)
+    {
+        error_print("Object %s is not a tree", checksum);
+        return WRONG_OBJECT_TYPE;
+    }
 
-    // return write_object(&obj);
-
-    // read_object("af5626b4a114abcb82d63db7c8082c3c4756e51b", &obj);
-
-    // debug_print("Object type is \"%s\"", obj.object_type);
-    // debug_print("Content size is %li", obj.size);
-    // debug_print("Content is %.*s", (int)obj.size, obj.content);
-
-    // free_object(&obj);
-
-    add_to_index(&index, "src/fs.c");
-
-    dump_index(&index);
-
-    save_index(&index);
-
-    free_index(&index);
+    get_tree(object.content, tree);
+    free_object(&object);
 
+    return 0;
+}
+
+int load_index(struct tree *index)
+{
+    if(!local_repo_exist() || !index_exist())
+    {
+        return REPO_NOT_INITIALIZED;
+    }
+
+    FILE* index_file = fopen(INDEX_FILE, "r");
+    struct stat buffer;
+    stat(INDEX_FILE, &buffer);
+
+    char* file_content = calloc(buffer.st_size + 1, sizeof(char));
+    fread(file_content, buffer.st_size, 1, index_file);
+    fclose(index_file);
+
+    get_tree(file_content, index);
+
+    free(file_content);
+
+    return FS_OK;
+}
+
+int save_index(struct tree *tree)
+{
+    if(!local_repo_exist())
+    {
+        return REPO_NOT_INITIALIZED;
+    }
+
+    FILE *index_file = fopen(INDEX_FILE"_cpy", "w");
+    if(index_exist == NULL)
+    {
+        return FS_ERROR;
+    }
+
+    struct object object;
+    tree_to_object(tree, &object);
+
+    fwrite(object.content, object.size, 1, index_file);
+    fclose(index_file);
+    free_object(&object);
+}
+
+int get_last_commit(struct object *commit)
+{
+    size_t head_size = 0;
+    if(!local_repo_exist() || !head_file_exist(&head_size) || !heads_dir_exist)
+    {
+        return REPO_NOT_INITIALIZED;
+    }
+
+    if(head_size == 0) return 0;
+
+    FILE *head_file = NULL;
+    head_file = fopen(HEAD_FILE, "r");
+    char head_path[head_size];
+    fread(head_path, head_size, 1, head_file);
+    fclose(head_file);
+
+    struct stat buffer = {0};
+    if (stat(head_path, &buffer) != 0) return 0;
+
+    char commit_checksum[buffer.st_size + 1];
+    memset(commit_checksum, 0, buffer.st_size + 1);
+    head_file = fopen(head_path, "r");
+    fread(commit_checksum, buffer.st_size, 1, head_file);
+    fclose(head_file);
+
+    int res = read_object(commit_checksum, commit);
+    if (res != 0) return FS_ERROR;
+
+    if (commit->object_type != COMMIT) return WRONG_OBJECT_TYPE;
+
+    return 0;
+}
+
+int update_head(char *new_head)
+{
+    size_t head_size = 0;
+    if(!local_repo_exist() || !head_file_exist(&head_size) || !heads_dir_exist)
+    {
+        return REPO_NOT_INITIALIZED;
+    }
+
+    FILE *file;
+
+    if(head_size != 0) {
+        FILE *head_file = fopen(HEAD_FILE, "r");
+        char branch[head_size];
+        fread(branch, head_size, 1, head_file);
+        fclose(head_file);
+        file = fopen(branch, "w");        
+    } else 
+    {
+        FILE *head_file = fopen(HEAD_FILE, "w");
+        fprintf(head_file, "%s/master", HEADS_DIR);
+        fclose(head_file);
+        file = fopen(HEADS_DIR"/master", "w");
+    }
+
+    fwrite(new_head, strlen(new_head), 1, file);
+    fclose(file);
     return 0;
 }
\ No newline at end of file
diff --git a/src/fs.h b/src/fs.h
index d28898a..f170f11 100644
--- a/src/fs.h
+++ b/src/fs.h
@@ -1,11 +1,14 @@
 #ifndef FS_H
 #define FS_H 1
 
-#include "objects.h"
+#include "types.h"
 
 #define LOCAL_REPO ".cgit"
 #define INDEX_FILE LOCAL_REPO"/index"
-#define OBJECTS_REPO LOCAL_REPO"/objects"
+#define OBJECTS_DIR LOCAL_REPO"/objects"
+#define REFS_DIR LOCAL_REPO"/refs"
+#define HEADS_DIR REFS_DIR"/heads"
+#define HEAD_FILE LOCAL_REPO"/HEAD"
 #define DEFAULT_DIR_MODE 0755
 #define DEFAULT_FILE_MODE 0444
 
@@ -15,13 +18,20 @@
 #define REPO_NOT_INITIALIZED (-10)
 #define OBJECT_ALREADY_EXIST (-20)
 #define OBJECT_DOES_NOT_EXIST (-21)
-#define FILE_NOT_FOUND (-22)
-#define ENTRY_NOT_FOUND (-23)
+#define WRONG_OBJECT_TYPE (-22)
+#define FILE_NOT_FOUND (-30)
+#define ENTRY_NOT_FOUND (-31)
 
 int local_repo_exist();
 int index_exist();
 
+int blob_from_file(char *filename, struct object *object);
 int write_object(struct object *obj);
 int read_object(char *checksum, struct object *obj);
+int save_index(struct tree *tree);
+int load_index(struct tree *index);
+int load_tree(char* checksum, struct tree *tree);
+int update_head(char *new_head);
+int get_last_commit(struct object *commit);
 
 #endif // FS_H
diff --git a/src/includes.h b/src/includes.h
index c5eb143..a584971 100644
--- a/src/includes.h
+++ b/src/includes.h
@@ -1,6 +1,8 @@
 #ifndef INCLUDES_H
 #define INCLUDES_H
 
+#define DIGEST_LENGTH 20
+
 #ifdef DEBUG
 #define debug_print(X, ...) \
     printf("[DEBUG] %s:%d: ", __FILE__, __LINE__); \
diff --git a/src/index.c b/src/index.c
deleted file mode 100644
index 42c266f..0000000
--- a/src/index.c
+++ /dev/null
@@ -1,133 +0,0 @@
-#include <stdlib.h>
-#include <string.h>
-
-#include "index.h"
-#include "includes.h"
-#include "fs.h"
-
-void free_entry(struct entry *entry)
-{
-    if (entry->checksum != NULL)
-        free(entry->checksum);
-    
-    if (entry->filename != NULL)
-        free(entry->filename);
-
-}
-
-void free_index(struct index *index)
-{
-    struct entry *current = index->first_entry;
-    struct entry *next;
-    while(current != NULL)
-    {
-        free_entry(current);
-        next = current->next;
-        free(current);
-        current = next;   
-    }
-}
-
-struct entry *find_entry(struct index *index, char* filename)
-{
-    struct entry *current = index->first_entry;
-    for (int i = 0; i < index->entries_size; i ++)
-    {
-        if (strncmp(filename, current->filename, strlen(filename)) == 0) {
-            return current;
-        }
-        current = current->next;
-    }
-
-    return NULL;
-}
-
-int add_to_index(struct index *index, char *filename)
-{
-    if(!local_repo_exist() || !index_exist())
-    {
-        return REPO_NOT_INITIALIZED;
-    }
-    
-    int result = FS_OK;
-    int new = 0;
-
-    struct entry *entry = find_entry(index, filename);
-    if (entry == NULL)
-    {
-        new = 1;
-        entry = calloc(sizeof(struct entry), 1);
-    } else {
-        free_entry(entry);
-    }
-
-    struct object object = {0};
-    if (blob_from_file(filename, &object) != 0)
-    {
-        return FILE_NOT_FOUND;
-    }
-
-    entry->filename = calloc(sizeof(char), strlen(filename) + 1);
-    strncat(entry->filename, filename, strlen(filename));
-    entry->checksum = calloc(sizeof(char), DIGEST_LENGTH * 2 + 1);
-    hash_object(&object, entry->checksum);
-    int res = write_object(&object);
-    if (res != FS_OK && res != OBJECT_ALREADY_EXIST)
-    {
-        defer(FS_ERROR);
-    }
-    
-    if(new)
-    {
-        if(index->entries_size == 0)
-        {
-            index->first_entry = entry;
-            index->last_entry = entry;
-        } else
-        {
-            entry->previous = index->last_entry;
-            index->last_entry->next = entry;
-            index->last_entry = entry;
-        }
-        index->entries_size = index->entries_size + 1;
-    }
-
-defer:
-    free_object(&object);
-    return result;
-}
-
-int remove_from_index(struct index *index, char *filename)
-{
-    if (!local_repo_exist() || !index_exist())
-    {
-        return REPO_NOT_INITIALIZED;
-    }
-
-    struct entry *entry = find_entry(index, filename);
-    if (entry == NULL)
-    {
-        return ENTRY_NOT_FOUND;
-    }
-
-    if(index->first_entry == entry)
-    {
-        index->first_entry = entry->next;
-    } else 
-    {
-        entry->previous->next = entry->next;
-    }
-
-    if (index->last_entry == entry)
-    {
-        index->last_entry = entry->previous;
-    } else 
-    {
-        entry->next->previous = entry->previous;
-    }
-
-    index->entries_size = index->entries_size - 1;
-    free_entry(entry);
-    free(entry);
-    return FS_OK;
-}
\ No newline at end of file
diff --git a/src/index.h b/src/index.h
deleted file mode 100644
index 74f632e..0000000
--- a/src/index.h
+++ /dev/null
@@ -1,28 +0,0 @@
-#ifndef INDEX_H
-#define INDEX_H
-
-#include <stddef.h>
-
-// Index file should follow the format
-// number of entries\n
-// entry1\n
-// entry2\n
-// ...
-struct entry {
-    char *checksum;
-    char *filename;
-    struct entry *previous;
-    struct entry *next;
-};
-
-struct index {
-    size_t entries_size;
-    struct entry *first_entry;
-    struct entry *last_entry;
-};
-
-void free_index(struct index *index);
-int add_to_index(struct index *index, char *filename);
-int remove_from_index(struct index *index, char *filename);
-
-#endif // INDEX_H
\ No newline at end of file
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..8230ccb
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,37 @@
+// Requirements
+// commit
+// branching
+// revert
+// pull/push
+
+#include <stdio.h>
+
+#include "commit.h"
+
+int main(int argc, char** argv) {
+    // struct object obj = {0};
+    // obj.content = "Hello, world!\n";
+    // obj.size = strlen(obj.content);
+    // obj.object_type = "blob";
+
+    // return write_object(&obj);
+
+    // read_object("af5626b4a114abcb82d63db7c8082c3c4756e51b", &obj);
+
+    // debug_print("Object type is \"%s\"", obj.object_type);
+    // debug_print("Content size is %li", obj.size);
+    // debug_print("Content is %.*s", (int)obj.size, obj.content);
+
+    // free_object(&obj);
+
+    // add_to_index(&index, "src/fs.c");
+    // add_to_index(&index, "src/test/foo");
+    // add_to_index(&index, ".gitignore");
+    // add_to_index(&index, "src/fs.h");
+
+    // dump_index(&tree);
+
+    commit();
+
+    return 0;
+}
\ No newline at end of file
diff --git a/src/objects.c b/src/objects.c
index afb35fe..54bd223 100644
--- a/src/objects.c
+++ b/src/objects.c
@@ -11,9 +11,28 @@
 #include "utils.h"
 #include "objects.h"
 
+char *object_type_str[3] = {
+    "blob", 
+    "tree",
+    "commit",
+};
+
+enum object_type str_to_object_type(char* str)
+{
+    if(strncmp("tree", str, 4) == 0)
+    {
+        return TREE;
+    } else if (strncmp("commit", str, 5) == 0)
+    {
+        return COMMIT;
+    }
+
+    return BLOB;
+}
+
 size_t header_size(struct object *obj)
 {
-    return strlen(obj->object_type) + 2 + decimal_len(obj->size);
+    return strlen(object_type_str[obj->object_type]) + 2 + decimal_len(obj->size);
 }
 
 size_t object_size(struct object *obj)
@@ -30,8 +49,9 @@ int full_object(struct object *obj, char *buffer, size_t buffer_size)
     assert(data_size <= buffer_size);
 
     char *writing = buffer;
-    memcpy(writing, obj->object_type, strlen(obj->object_type));
-    writing += strlen(obj->object_type);
+    char *type = object_type_str[obj->object_type];
+    memcpy(writing, type, strlen(type));
+    writing += strlen(type);
     memcpy(writing, " ", 1);
     writing ++;
     memcpy(writing, hr_size, strlen(hr_size));
@@ -86,8 +106,7 @@ int uncompress_object(struct object *obj, char* compressed, uLongf comp_size)
     char *content_type_tmp = strtok(deflated, " ");
 
     obj->size = content_size;
-    obj->object_type = malloc(strlen(content_type_tmp) + 1);
-    strncpy(obj->object_type, content_type_tmp, strlen(content_type_tmp) + 1);
+    obj->object_type = str_to_object_type(content_type_tmp);
     obj->content = malloc(obj->size);
     memcpy(obj->content, deflated + header_size, obj->size);
     free(deflated);
@@ -107,25 +126,6 @@ int compress_object(struct object *obj, char* compressed, uLongf *comp_size)
     return res;
 }
 
-int blob_from_file(char *filename, struct object *object)
-{
-    FILE* file = fopen(filename, "r");
-    if (file == NULL)
-        return -1;
-
-    struct stat file_info;
-    if (stat(filename, &file_info) != 0)
-        return -1;
-    
-    object->object_type = "blob";
-    object->size = file_info.st_size;
-    object->content = realloc(object->content, object->size);
-    fread(object->content, 1, object->size, file);
-    fclose(file);
-
-    return 0;
-}
-
 void free_object(struct object *obj)
 {
     if (obj->content != NULL)
diff --git a/src/objects.h b/src/objects.h
index 5023e53..42fe12f 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4,22 +4,16 @@
 #include <stddef.h>
 #include <zconf.h>
 
-#define DIGEST_LENGTH 20
+#include "types.h"
+
 #define HEADER_MAX_SIZE 20
 
-struct object
-{
-    char* content;
-    size_t size;
-    char* object_type;
-};
-
+enum object_type str_to_object_type(char* str);
 size_t object_size(struct object *obj);
 int full_object(struct object *obj, char* buffer, size_t buffer_size);
 int uncompress_object(struct object *obj, char* compressed, uLongf comp_size);
 int compress_object(struct object *obj, char* compressed, uLongf *comp_size);
 void hash_object(struct object *obj, char* result);
-int blob_from_file(char *filename, struct object *object);
 void free_object(struct object *obj);
 
 #endif // OBJECTS_H
diff --git a/src/tree.c b/src/tree.c
new file mode 100644
index 0000000..4912459
--- /dev/null
+++ b/src/tree.c
@@ -0,0 +1,248 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "tree.h"
+#include "includes.h"
+#include "fs.h"
+#include "objects.h"
+#include "utils.h"
+
+void free_entry(struct entry *entry)
+{
+    if (entry->checksum != NULL)
+        free(entry->checksum);
+    
+    if (entry->filename != NULL)
+        free(entry->filename);
+
+}
+
+void free_tree(struct tree *tree)
+{
+    struct entry *current = tree->first_entry;
+    struct entry *next;
+    while(current != NULL)
+    {
+        free_entry(current);
+        next = current->next;
+        free(current);
+        current = next;   
+    }
+}
+
+struct entry *find_entry(struct tree *tree, char* filename)
+{
+    struct entry *current = tree->first_entry;
+    for (int i = 0; i < tree->entries_size; ++i)
+    {
+        if (strcmp(filename, current->filename) == 0) {
+            return current;
+        }
+        current = current->next;
+    }
+
+    return NULL;
+}
+
+void get_tree(char* content, struct tree *tree)
+{
+    char* current_line;
+    current_line = strtok(content, "\n");
+    tree->entries_size = strtol(current_line, NULL, 10);
+    tree->first_entry = NULL;
+    tree->last_entry = NULL;
+
+    for(int i = 0; i < tree->entries_size; i++)
+    {
+        current_line = strtok(NULL, "\n");
+        int j = 0;
+        while(current_line[j] != ' ')
+        {
+            j++;
+        }
+
+        char* checksum = calloc(j + 1, sizeof(char));
+        char* filename = calloc(strlen(current_line) - j, sizeof(char));
+        strncat(checksum, current_line, j);
+        strncat(filename, current_line + j + 1, strlen(current_line) - j);
+
+        struct entry *entry = calloc(1, sizeof(struct entry));
+        entry->checksum = checksum;
+        entry->filename = filename;
+        entry->next = NULL;
+
+        if(i == 0)
+        {
+            tree->first_entry = entry;
+            tree->last_entry = entry;
+        } else 
+        {
+            entry->previous = tree->last_entry;
+            tree->last_entry->next = entry;
+        }
+        tree->last_entry = entry;
+    }
+}
+
+int add_to_tree(struct tree *tree, struct object *object, char *filename)
+{
+
+    int new = 0;
+    struct entry *entry = find_entry(tree, filename);
+    if (entry == NULL)
+    {
+        new = 1;
+        entry = calloc(sizeof(struct entry), 1);
+    } else {
+        free_entry(entry);
+    }
+
+    entry->filename = calloc(sizeof(char), strlen(filename) + 1);
+    strncat(entry->filename, filename, strlen(filename));
+    entry->checksum = calloc(sizeof(char), DIGEST_LENGTH * 2 + 1);
+    hash_object(object, entry->checksum);
+    // int res = write_object(object);
+    // if (res != FS_OK && res != OBJECT_ALREADY_EXIST)
+    // {
+    //     return res;
+    // }
+    
+    if(new)
+    {
+        if (tree->entries_size == 0)
+        {
+            tree->first_entry = entry;
+            tree->last_entry = entry;
+        } else
+        {
+            struct entry *current = tree->first_entry;
+            while (current != NULL && (strncmp(current->filename, entry->filename, strlen(entry->filename)) < 0))
+            {
+                current = current->next;
+            }
+
+            if (current == NULL)
+            {
+                tree->last_entry->next = entry;
+                entry->previous = tree->last_entry;
+                tree->last_entry = entry;
+            } else {
+                if(current == tree->first_entry)
+                {
+                    tree->first_entry = entry;
+                } else {
+                    current->previous->next = entry;
+                    entry->previous = current->previous;
+                }
+
+                entry->next = current;
+                current->previous = entry;
+            }
+        }
+        tree->entries_size ++;
+    }
+}
+
+int add_to_index(struct tree *index, char *filename)
+{
+    struct object object = {0};
+    if (blob_from_file(filename, &object) != FS_OK)
+    {
+        return FILE_NOT_FOUND;
+    }
+
+    add_to_tree(index, &object, filename);
+
+    free_object(&object);
+    return FS_OK;
+}
+
+int remove_from_index(struct tree *index, char *filename)
+{
+    if (!local_repo_exist() || !index_exist())
+    {
+        return REPO_NOT_INITIALIZED;
+    }
+
+    struct entry *entry = find_entry(index, filename);
+    if (entry == NULL)
+    {
+        return ENTRY_NOT_FOUND;
+    }
+
+    if(index->first_entry == entry)
+    {
+        index->first_entry = entry->next;
+    } else 
+    {
+        entry->previous->next = entry->next;
+    }
+
+    if (index->last_entry == entry)
+    {
+        index->last_entry = entry->previous;
+    } else 
+    {
+        entry->next->previous = entry->previous;
+    }
+
+    index->entries_size = index->entries_size - 1;
+    free_entry(entry);
+    free(entry);
+    return FS_OK;
+}
+
+int tree_to_object(struct tree *tree, struct object *object)
+{
+    object->object_type = TREE;
+    object->content = calloc(1, decimal_len(tree->entries_size) + 2);
+    object->size = decimal_len(tree->entries_size) + 2;
+    sprintf(object->content, "%li\n", tree->entries_size);
+
+    struct entry *current = tree->first_entry;
+    for(int i = 0; i < tree->entries_size; i++)
+    {
+        size_t entry_size = DIGEST_LENGTH * 2 + 2 + strlen(current->filename);
+        char tmp[entry_size + 1];
+        object->size = object->size + entry_size;
+        object->content = realloc(object->content, object->size);
+        sprintf(tmp, "%s %s\n", current->checksum, current->filename);
+        strncat(object->content, tmp, entry_size);
+        current = current->next;
+    }
+
+    object->size --;
+}
+
+int add_object_to_tree(struct tree *tree, char* filename, struct object *source)
+{
+    char top_folder_name[strlen(filename)];
+    char path_left[strlen(filename)];
+    int res = get_top_folder(filename, top_folder_name, path_left); 
+    if (res > 0)
+    {
+        struct tree subtree = {0};
+        struct object result = {0};
+        struct entry *top_folder = find_entry(tree, top_folder_name);
+        if(top_folder != NULL)
+        {
+            load_tree(top_folder->checksum, &subtree);
+            remove_from_index(tree, top_folder->filename);
+        }
+
+        add_to_tree(&subtree, source, path_left);
+
+        add_object_to_tree(&subtree, path_left, source);
+
+        tree_to_object(&subtree, &result);
+        write_object(&result);
+        remove_from_index(tree, filename);
+        add_to_tree(tree, &result, top_folder_name);
+        free_object(&result);
+        free_tree(&subtree);
+    } else {
+        add_to_tree(tree, source, filename);
+        write_object(source);
+    }
+}
diff --git a/src/tree.h b/src/tree.h
new file mode 100644
index 0000000..9e4824e
--- /dev/null
+++ b/src/tree.h
@@ -0,0 +1,22 @@
+#ifndef INDEX_H
+#define INDEX_H
+
+#include <stddef.h>
+#include "types.h"
+
+// Index file should follow the format
+// number of entries\n
+// entry1\n
+// entry2\n
+// ...
+
+void free_tree(struct tree *index);
+struct entry *find_entry(struct tree *index, char* filename);
+void get_tree(char* content, struct tree *tree);
+int add_to_tree(struct tree *tree, struct object *object, char *filename);
+int add_to_index(struct tree *index, char *filename);
+int remove_from_index(struct tree *index, char *filename);
+int tree_to_object(struct tree *tree, struct object *object);
+int add_object_to_tree(struct tree *tree, char* filename, struct object *source);
+
+#endif // INDEX_H
\ No newline at end of file
diff --git a/src/types.h b/src/types.h
new file mode 100644
index 0000000..1cb3b98
--- /dev/null
+++ b/src/types.h
@@ -0,0 +1,40 @@
+#ifndef TYPES_H
+#define TYPES_H 1
+
+#include <stddef.h>
+
+enum object_type
+{
+    BLOB,
+    TREE,
+    COMMIT
+};
+
+struct object
+{
+    char* content;
+    size_t size;
+    enum object_type object_type;
+};
+
+struct entry {
+    char *checksum;
+    char *filename;
+    struct entry *previous;
+    struct entry *next;
+};
+
+struct tree {
+    size_t entries_size;
+    struct entry *first_entry;
+    struct entry *last_entry;
+};
+
+struct commit
+{
+    char *tree;
+    char *parent;
+    char *author;
+};
+
+#endif // TYPES_H
\ No newline at end of file
diff --git a/src/utils.c b/src/utils.c
index 83b58af..780606d 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -1,4 +1,5 @@
 #include <math.h>
+#include <stdio.h>
 
 #include "utils.h"
 
@@ -9,3 +10,15 @@ int decimal_len(size_t size)
 
     return floor(log10(size)) + 1;
 }
+
+int get_top_folder(char* path, char* top_folder, char* left) 
+{
+    int i = 0;
+    for (;path[i] != '/' && path[i] != '\0'; i++);
+    if (path[i] == '\0') return 0;
+    path[i] = '\0';
+    sprintf(top_folder, "%s", path);
+    sprintf(left, "%s", path + i + 1);
+    path[i] = '/';
+    return 1;
+}
diff --git a/src/utils.h b/src/utils.h
index e4ef1e2..5ec5913 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -4,5 +4,6 @@
 #include <stddef.h>
 
 int decimal_len(size_t size);
+int get_top_folder(char* path, char* top_folder, char* left);
 
 #endif // UTILS_H
\ No newline at end of file