1 files changed, 75 insertions, 0 deletions
diff --git a/src/main/kotlin/Path.kt b/src/main/kotlin/Path.kt
new file mode 100644
index 0000000..0e209cf
--- /dev/null
+++ b/src/main/kotlin/Path.kt
@@ -0,0 +1,75 @@
+import util.expandWith
+
+sealed interface Path {
+	val parts: List<String>
+	fun toAbsolutePath(relativeTo: Absolute): Absolute {
+		return relativeTo.resolve(this)
+	}
+
+	fun resolve(path: Path): Path
+
+	companion object {
+		val root = Absolute(listOf())
+
+		fun ofShell(string: String, userHome: Absolute): Path =
+			ofShell(string.split("/"), userHome)
+
+		fun ofShell(vararg parts: String, userHome: Absolute): Path =
+			ofShell(parts.toList(), userHome)
+
+		fun of(vararg parts: String): Path =
+			of(parts.toList())
+
+		fun of(string: String): Path =
+			of(string.split("/"))
+
+		fun ofShell(parts: List<String>, userHome: Absolute): Path {
+			if (parts.firstOrNull() == "~")
+				return userHome.resolve(Relative(parts.subList(1, parts.size).filter { it.isNotEmpty() }))
+			return of(parts)
+		}
+
+		fun of(parts: List<String>): Path {
+			if (parts.isEmpty())
+				return root
+			if (parts[0] == "") // Starts with a /
+				return Absolute(parts.subList(1, parts.size).filter { it.isNotEmpty() })
+			return Relative(parts.filter { it.isNotEmpty() })
+		}
+	}
+
+	data class Relative internal constructor(override val parts: List<String>) : Path {
+		override fun resolve(path: Path): Path {
+			if (path is Absolute) return path
+			return Relative(this.parts + path.parts)
+		}
+	}
+
+	data class Absolute internal constructor(override val parts: List<String>) : Path {
+		override fun resolve(path: Path): Absolute {
+			if (path is Absolute) return path
+			return Absolute(this.parts + path.parts)
+		}
+
+		fun relativize(path: Path): Relative = when (path) {
+			is Relative -> path
+			is Absolute -> {
+				var commonPrefix = true
+				val partList = mutableListOf<String>()
+				var returns = 0
+				for ((idx, part) in path.parts.withIndex()) {
+					if (idx < this.parts.size) {
+						if (this.parts[idx] == part && commonPrefix) {
+							continue
+						} else {
+							commonPrefix = false
+							returns++
+						}
+					}
+					partList.add(part)
+				}
+				Relative(List(returns) { ".." } + partList)
+			}
+		}
+	}
+}