[backport] Add uri.relativeTo

Original: cca63f7

1 files changed, 40 insertions, 0 deletions

diff --git a/core/src/main/kotlin/Utilities/Uri.kt b/core/src/main/kotlin/Utilities/Uri.kt
new file mode 100644
index 00000000..5b520188
--- /dev/null
+++ b/core/src/main/kotlin/Utilities/Uri.kt
@@ -0,0 +1,40 @@
+package org.jetbrains.dokka
+
+import java.net.URI
+
+
+fun URI.relativeTo(uri: URI): URI {
+    // Normalize paths to remove . and .. segments
+    val base = uri.normalize()
+    val child = this.normalize()
+
+    fun StringBuilder.appendRelativePath() {
+        // Split paths into segments
+        var bParts = base.path.split('/').dropLastWhile { it.isEmpty() }
+        val cParts = child.path.split('/').dropLastWhile { it.isEmpty() }
+
+        // Discard trailing segment of base path
+        if (bParts.isNotEmpty() && !base.path.endsWith("/")) {
+            bParts = bParts.dropLast(1)
+        }
+
+        // Compute common prefix
+        val commonPartsSize = bParts.zip(cParts).count { (basePart, childPart) -> basePart == childPart }
+        bParts.drop(commonPartsSize).joinTo(this, separator = "") { "../" }
+        cParts.drop(commonPartsSize).joinTo(this, separator = "/")
+    }
+
+    return URI.create(buildString {
+        if (base.path != child.path) {
+            appendRelativePath()
+        }
+        child.rawQuery?.let {
+            append("?")
+            append(it)
+        }
+        child.rawFragment?.let {
+            append("#")
+            append(it)
+        }
+    })
+}
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