Implement toString() for objects (#4)

> Search for specific commit by hash or metadata and print its content.

To satisfy this final requirement, we need to have `toString()` implemented for version manager `Object`s which will allow them to be easily (and nicely) printed if needed (includes tests).

Reviewed-on: #4

src/main/kotlin/tinyvm/Tree.kt

@@ -15,9 +15,22 @@ class Tree(val nodes: Map<String, Node>) : Node("tree") {
             nodes.map { (name, node) ->
                 "${node.type} $name\u0000${node.hash()}"
             }.sorted().joinToString()
+
+    override fun toString(): String =
+        "tree ${hash()}\n" +
+            nodes.map { (name, node) ->
+                when (node) {
+                    is Tree -> "+$name/\n"
+                    is Blob -> "+$name\n"
+                } + node.toString().leftMargin()
+            }.sorted().joinToString("\n")
 }
 
 /**
  * A blob is a data container.
  */
-class Blob(override val data: String) : Node("blob")
+class Blob(override val data: String) : Node("blob") {
+    override fun toString(): String = "blob ${hash()}\n${data.leftMargin()}"
+}
+
+private fun String.leftMargin(): String = split('\n').joinToString("\n") { "| $it" }

src/test/kotlin/tinyvm/RepositoryTest.kt

@@ -18,22 +18,22 @@ internal class RepositoryTest {
                 tree =
                     Tree(
                         mapOf(
+                            "dir2" to
+                                Tree(
+                                    mapOf(
+                                        "test1.txt" to Blob("This is a second file"),
+                                    ),
+                                ),
                             "dir1" to
                                 Tree(
                                     mapOf(
                                         "test1.txt" to Blob("Hello World!"),
                                     ),
                                 ),
-                            "dir2" to
-                                Tree(
-                                    mapOf(
-                                        "test2.txt" to Blob("This is a second file"),
-                                    ),
-                                ),
                         ),
                     ),
                 author = Author("Gleb Koval", "gleb@koval.net"),
-                message = "Move test1.txt and add dir2/test2.txt",
+                message = "Move test1.txt to dir1 and add dir2/test1.txt",
                 timestamp = Instant.ofEpochSecond(50),
             ),
             Commit(
@@ -49,7 +49,7 @@ internal class RepositoryTest {
                             "dir2" to
                                 Tree(
                                     mapOf(
-                                        "test2.txt" to Blob("This is a second file"),
+                                        "test1.txt" to Blob("This is a second file"),
                                     ),
                                 ),
                             "README.md" to Blob("# This is a test repo!"),
@@ -117,4 +117,39 @@ internal class RepositoryTest {
         assertEquals(committed, repository.findCommit { it.message.matches("Move.*".toRegex()) })
         assertEquals(null, repository.getCommit("00000000000000000000"))
     }
+
+    @Test
+    fun `can display commit`() {
+        assertEquals(
+            """
+            commit 804c6f0c66da0ea0eab8ac29f23a627e03a962b2
+            tree aaebbb258bce30749fc302cbd161b78462252a32
+            author Gleb Koval <gleb@koval.net>
+            timestamp 0
+            
+            Add test1.txt
+            """.trimIndent(),
+            commits[0].toString(),
+        )
+    }
+
+    @Test
+    fun `can display tree`() {
+        assertEquals(
+            """
+            tree 048b8e267dd7a6c5d4849d59f6ff82e6ae948f13
+            +dir1/
+            | tree aaebbb258bce30749fc302cbd161b78462252a32
+            | +test1.txt
+            | | blob c57eff55ebc0c54973903af5f72bac72762cf4f4
+            | | | Hello World!
+            +dir2/
+            | tree 0e14cbdba02924cd63a58c2492fc3dd05dc682bd
+            | +test1.txt
+            | | blob da3fcc31cbc16fcbb7526d68771f77e7e7f02fb1
+            | | | This is a second file
+            """.trimIndent(),
+            commits[1].tree.toString(),
+        )
+    }
 }