Count file diff by token, not by length of string (#63)

* 1.1.23

* 1.1.24

* feat(package.json): add @dqbd/tiktoken dependency

refactor(generateCommitMessageFromGitDiff.ts): add tokenCount function to count the number of tokens in a string
refactor(generateCommitMessageFromGitDiff.ts): change the way the length of INIT_MESSAGES_PROMPT is calculated to use tokenCount function
refactor(generateCommitMessageFromGitDiff.ts): change the way the length of diff is calculated to use tokenCount function

refactor(generateCommitMessageFromGitDiff.ts): rename function parameter from diff to fileDiff and update function calls accordingly
feat(generateCommitMessageFromGitDiff.ts): add tokenCount function to count tokens in fileDiff and use it to check if fileDiff is bigger than MAX_REQ_TOKENS

feat(utils): add tokenCount function to count the number of tokens in a string
refactor(utils/mergeStrings.ts): use tokenCount function to count the number of tokens in a string instead of checking the length of the concatenated string

---------

Co-authored-by: di-sukharev <dim.sukharev@gmail.com>

src/generateCommitMessageFromGitDiff.ts

@@ -6,6 +6,7 @@ import { api } from './api';
 import { getConfig } from './commands/config';
 import { mergeStrings } from './utils/mergeStrings';
 import { i18n, I18nLocals } from './i18n';
+import { tokenCount } from './utils/tokenCount';
 
 const config = getConfig();
 const translation = i18n[(config?.language as I18nLocals) || 'en'];
@@ -13,12 +14,10 @@ const translation = i18n[(config?.language as I18nLocals) || 'en'];
 const INIT_MESSAGES_PROMPT: Array<ChatCompletionRequestMessage> = [
   {
     role: ChatCompletionRequestMessageRoleEnum.System,
-    content: `You are to act as the author of a commit message in git. Your mission is to create clean and comprehensive commit messages in the conventional commit convention. I'll send you an output of 'git diff --staged' command, and you convert it into a commit message. ${
-      config?.emoji
-        ? 'Use Gitmoji convention to preface the commit'
-        : 'Do not preface the commit with anything'
-    }, use the present tense. ${
-      config?.description
+    content: `You are to act as the author of a commit message in git. Your mission is to create clean and comprehensive commit messages in the conventional commit convention. I'll send you an output of 'git diff --staged' command, and you convert it into a commit message. ${config?.emoji
+      ? 'Use Gitmoji convention to preface the commit'
+      : 'Do not preface the commit with anything'
+      }, use the present tense. ${config?.description
         ? 'Add a short description of what commit is about after the commit message. Don\'t start it with "This commit", just describe the changes.'
         : "Don't add any descriptions to the commit, only commit message."
     } Use ${translation.localLanguage} to answer.`
@@ -80,16 +79,16 @@ interface GenerateCommitMessageError {
 }
 
 const INIT_MESSAGES_PROMPT_LENGTH = INIT_MESSAGES_PROMPT.map(
-  (msg) => msg.content
-).join('').length;
+  (msg) => tokenCount(msg.content) + 4
+).reduce((a, b) => a + b, 0);
 
 const MAX_REQ_TOKENS = 3900 - INIT_MESSAGES_PROMPT_LENGTH;
 
 export const generateCommitMessageWithChatCompletion = async (
   diff: string
 ): Promise<string | GenerateCommitMessageError> => {
-  try {
-    if (diff.length >= MAX_REQ_TOKENS) {
+ try {
+    if (tokenCount(diff) >= MAX_REQ_TOKENS) {
       const commitMessagePromises = getCommitMsgsPromisesFromFileDiffs(diff);
 
       const commitMessages = await Promise.all(commitMessagePromises);
@@ -144,7 +143,7 @@ function getCommitMsgsPromisesFromFileDiffs(diff: string) {
   const commitMessagePromises = [];
 
   for (const fileDiff of mergedFilesDiffs) {
-    if (fileDiff.length >= MAX_REQ_TOKENS) {
+    if (tokenCount(fileDiff) >= MAX_REQ_TOKENS) {
       // if file-diff is bigger than gpt context — split fileDiff into lineDiff
       const messagesPromises = getMessagesPromisesByLines(fileDiff, separator);
 

src/utils/mergeStrings.ts

@@ -1,8 +1,9 @@
+import { tokenCount } from './tokenCount'
 export function mergeStrings(arr: string[], maxStringLength: number): string[] {
   const mergedArr: string[] = [];
   let currentItem: string = arr[0];
   for (const item of arr.slice(1)) {
-    if (currentItem.length + item.length <= maxStringLength) {
+    if (tokenCount(currentItem + item) <= maxStringLength) {
       currentItem += item;
     } else {
       mergedArr.push(currentItem);

src/utils/tokenCount.ts

@@ -0,0 +1,14 @@
+import { Tiktoken } from "@dqbd/tiktoken/lite"
+import cl100k_base from "@dqbd/tiktoken/encoders/cl100k_base.json" assert{type: "json"}
+
+export function tokenCount(content: string): number {
+    const encoding = new Tiktoken(
+        cl100k_base.bpe_ranks,
+        cl100k_base.special_tokens,
+        cl100k_base.pat_str
+    );
+    const tokens = encoding.encode(content);
+    encoding.free();
+
+    return tokens.length;
+}