From 1e9c17d09e2852d2e1c25268fd05541e4eec843f Mon Sep 17 00:00:00 2001
From: Severiano Badajoz <sbadajoz@chanzuckerberg.com>
Date: Thu, 28 May 2020 10:43:36 -0700
Subject: [PATCH] accurately compute largest possible string

---
 client/src/components/util/truncate.js | 94 ++++++++++++++++++++++----
 1 file changed, 82 insertions(+), 12 deletions(-)

diff --git a/client/src/components/util/truncate.js b/client/src/components/util/truncate.js
index c61e0ee8..5824dba5 100644
--- a/client/src/components/util/truncate.js
+++ b/client/src/components/util/truncate.js
@@ -31,26 +31,94 @@ export default class Truncate extends Component {
     return this.fontIsLoaded ? "Roboto Condensed" : "Helvetica Neue";
   }
 
+  computeLargestTruncatedString = (
+    str,
+    maxSize,
+    params,
+    length = str.length - 1,
+    lastLength = 0,
+    close = -1
+  ) => {
+    // Generate the truncated string with ellipses(not if full string)
+    const shortenedString =
+      length === str.length - 1
+        ? str
+        : `${str.slice(0, length)}…${str.slice(-length / 2)}`;
+    // Measure the size of that string
+    const renderedSize = pixelWidth(shortenedString, params);
+
+    // If that full length string is smaller than the maxSize don't return a truncated string
+    if (renderedSize < maxSize && length === str.length - 1) {
+      return null;
+    }
+    // Base case: If we've narrowed down to a length, return the closest string
+    if (length === lastLength) {
+      console.log("RETURNING", { length, lastLength, renderedSize });
+      return `${str.slice(0, close)}…${str.slice(-close / 2)}`;
+    }
+    // If the current size is longer than max
+    if (renderedSize > maxSize) {
+      console.log({
+        length,
+        lastLength,
+        renderedSize,
+        close,
+        size: "big",
+      });
+      // If we're only one off from the closest string so far, just return the closest string
+      if (length - close === 1) {
+        console.log("RETURNING", { length, lastLength, renderedSize });
+
+        return `${str.slice(0, close)}…${str.slice(-close / 2)}`;
+      }
+      // Otherwise recursively call with half the current length
+      return this.computeLargestTruncatedString(
+        str,
+        maxSize,
+        params,
+        length < lastLength
+          ? length / 2
+          : Math.floor(Math.floor((length - lastLength) / 2) + lastLength),
+        length,
+        close
+      );
+    }
+    // If the current size is smaller than the max
+    if (renderedSize < maxSize) {
+      console.log({
+        length,
+        lastLength,
+        renderedSize,
+        close,
+        size: "small",
+      });
+      // Save this length as the closest so far
+      close = length;
+      // Recursively call with a larger string
+      return this.computeLargestTruncatedString(
+        str,
+        maxSize,
+        params,
+        Math.floor((lastLength - length) / 2) + length,
+        length,
+        close
+      );
+    }
+    console.log("RETURNING", { length, lastLength, renderedSize });
+
+    return shortenedString;
+  };
+
   maybeTruncateString = (str, maxSize, fontSize, bold, italic) => {
     const activeFont = Truncate.getLoadedFont();
-
-    const renderedSize = pixelWidth(str, {
+    console.log({ activeFont });
+    return this.computeLargestTruncatedString(str, maxSize, {
       font: activeFont,
       size: fontSize,
       map: widthsMap,
       bold,
       italic,
     });
-    let truncatedString = null;
-    if (renderedSize > maxSize) {
-      const percentage = renderedSize / maxSize;
-      const newLength = str.length / percentage;
-      truncatedString = `${str.slice(0, newLength / 2)}…${str.slice(
-        -newLength / 2
-      )}`;
-    }
-
-    return truncatedString;
   };
 
   render() {
@@ -69,6 +137,8 @@ export default class Truncate extends Component {
         bold,
         italic
       );
+      console.log({ truncatedString });
+
       // Only make tooltip if string has to be truncated
       if (truncatedString) {
         // clone children, changing the children(text) to the truncated string