merge: Add support for trace writing

This pull request extends the trace API to support writing new traces.

- Unify columns of different tables 
- Support column lookup via index
- Use index lookup in trace loader 
- Add property for describing partition keys
- Simplify TraceFormat SPI interface
- Add support for writing traces

**Breaking API Changes**

- `TraceFormat` SPI interface has been redesigned.

2 files changed, 86 insertions, 5 deletions

diff --git a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TableDetails.kt b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TableDetails.kt
new file mode 100644
index 00000000..1a9b9ee1
--- /dev/null
+++ b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TableDetails.kt
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.trace.spi
+
+import org.opendc.trace.Table
+import org.opendc.trace.TableColumn
+
+/**
+ * A class used by the [TraceFormat] interface for describing the metadata of a [Table].
+ *
+ * @param columns The available columns in the table.
+ * @param partitionKeys The table columns that act as partition keys for the table.
+ */
+public data class TableDetails(
+    val columns: List<TableColumn<*>>,
+    val partitionKeys: List<TableColumn<*>> = emptyList()
+)
diff --git a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TraceFormat.kt b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TraceFormat.kt
index 54029fcf..f2e610db 100644
--- a/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TraceFormat.kt
+++ b/opendc-trace/opendc-trace-api/src/main/kotlin/org/opendc/trace/spi/TraceFormat.kt
@@ -22,8 +22,9 @@
 
 package org.opendc.trace.spi
 
-import org.opendc.trace.Trace
-import java.net.URL
+import org.opendc.trace.TableReader
+import org.opendc.trace.TableWriter
+import java.nio.file.Path
 import java.util.*
 
 /**
@@ -36,11 +37,52 @@ public interface TraceFormat {
     public val name: String
 
     /**
-     * Open a new [Trace] with this provider.
+     * Construct an empty trace at [path].
      *
-     * @param url A reference to the trace.
+     * @param path The path where to create the empty trace.
+     * @throws IllegalArgumentException If [path] is invalid.
+     * @throws UnsupportedOperationException If the table does not support trace creation.
      */
-    public fun open(url: URL): Trace
+    public fun create(path: Path)
+
+    /**
+     * Return the name of the tables available in the trace at the specified [path].
+     *
+     * @param path The path to the trace.
+     * @return The list of tables available in the trace.
+     */
+    public fun getTables(path: Path): List<String>
+
+    /**
+     * Return the details of [table] in the trace at the specified [path].
+     *
+     * @param path The path to the trace.
+     * @param table The name of the table to obtain the details for.
+     * @throws IllegalArgumentException If [table] does not exist.
+     * @return The [TableDetails] for the specified [table].
+     */
+    public fun getDetails(path: Path, table: String): TableDetails
+
+    /**
+     * Open a [TableReader] for the specified [table].
+     *
+     * @param path The path to the trace to open.
+     * @param table The name of the table to open a [TableReader] for.
+     * @throws IllegalArgumentException If [table] does not exist.
+     * @return A [TableReader] instance for the table.
+     */
+    public fun newReader(path: Path, table: String): TableReader
+
+    /**
+     * Open a [TableWriter] for the specified [table].
+     *
+     * @param path The path to the trace to open.
+     * @param table The name of the table to open a [TableWriter] for.
+     * @throws IllegalArgumentException If [table] does not exist.
+     * @throws UnsupportedOperationException If the format does not support writing.
+     * @return A [TableWriter] instance for the table.
+     */
+    public fun newWriter(path: Path, table: String): TableWriter
 
     /**
      * A helper object for resolving providers.
@@ -49,6 +91,7 @@ public interface TraceFormat {
         /**
          * A list of [TraceFormat] that are available on this system.
          */
+        @JvmStatic
         public val installedProviders: List<TraceFormat> by lazy {
             val loader = ServiceLoader.load(TraceFormat::class.java)
             loader.toList()
@@ -57,6 +100,7 @@ public interface TraceFormat {
         /**
          * Obtain a [TraceFormat] implementation by [name].
          */
+        @JvmStatic
         public fun byName(name: String): TraceFormat? = installedProviders.find { it.name == name }
     }
 }