feat(strings): add tab conversion fns

thi-ng · Jan 8, 2021 · aefdd97 · aefdd97
1 parent 2a283c0
commit aefdd97
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diff --git a/packages/strings/src/index.ts b/packages/strings/src/index.ts
@@ -21,6 +21,7 @@ export * from "./repeat";
 export * from "./slugify";
 export * from "./splice";
 export * from "./split";
+export * from "./tabs";
 export * from "./trim";
 export * from "./truncate";
 export * from "./truncate-left";

diff --git a/packages/strings/src/tabs.ts b/packages/strings/src/tabs.ts
@@ -0,0 +1,94 @@
+import { repeat } from "./repeat";
+
+const nextTab = (x: number, tabSize: number) =>
+    Math.floor((x + tabSize) / tabSize) * tabSize;
+
+/**
+ * Multi-line version of {@link tabsToSpacesLine}.
+ *
+ * @example
+ * ```ts
+ * console.log(
+ *   tabsToSpaces("0\t1\t2", 10)
+ *   + "\n" +
+ *   tabsToSpaces("0\t45\t890\t\t6\t0")
+ *   + "\n" +
+ *   tabsToSpaces("^\t^\t^\t^\t^\t^")
+ * );
+ * // 0         1         2
+ * // 0   45  890     6   0
+ * // ^   ^   ^   ^   ^   ^
+ * ```
+ *
+ * @param src
+ * @param tabSize
+ */
+export const tabsToSpaces = (src: string, tabSize = 4) =>
+    src
+        .split(/\r?\n/g)
+        .map((line) => tabsToSpacesLine(line, tabSize))
+        .join("\n");
+
+/**
+ * Takes a single line string and converts all tab characters to spaces, using
+ * given `tabSize`.
+ *
+ * @param line
+ * @param tabSize
+ */
+export const tabsToSpacesLine = (line: string, tabSize = 4) => {
+    let res = "";
+    let words = line.split(/\t/g);
+    let n = words.length - 1;
+    for (let i = 0; i < n; i++) {
+        const w = words[i];
+        res += w;
+        res += repeat(" ", nextTab(res.length, tabSize) - res.length);
+    }
+    res += words[n];
+    return res;
+};
+
+/**
+ * Multi-line version of {@link spacesToTabsLine}.
+ *
+ * @param src
+ * @param tabSize
+ */
+export const spacesToTabs = (src: string, tabSize = 4) =>
+    src
+        .split(/\r?\n/g)
+        .map((line) => spacesToTabsLine(line, tabSize))
+        .join("\n");
+
+/**
+ * Takes a single line string and converts all tab characters to spaces, using
+ * given `tabSize`. Inverse op of {@link tabsToSpacesLine}.
+ *
+ * @param line
+ * @param tabSize
+ */
+export const spacesToTabsLine = (line: string, tabSize = 4) => {
+    const re = /\s{2,}/g;
+    let i = 0;
+    let res = "";
+    let m: RegExpExecArray | null;
+    while ((m = re.exec(line))) {
+        const numSpaces = m[0].length;
+        res += line.substring(i, m.index);
+        i = m.index;
+        const end = m.index + numSpaces;
+        while (i < end) {
+            const j = nextTab(i, tabSize);
+            if (j <= end) {
+                res += "\t";
+                i = j;
+            } else {
+                res += repeat(" ", end - i);
+                i = end;
+            }
+        }
+        i = end;
+    }
+    return res + line.substr(i);
+};