Adds macro compiler

src/main/java/com/amazon/ion/impl/macro/Macro.kt

@@ -1,23 +1,45 @@
 package com.amazon.ion.impl.macro
 
-import java.math.BigDecimal
-
 /**
  * Marker interface for Macros
  */
-sealed interface Macro
+sealed interface Macro {
+    val signature: List<Parameter>
+
+    data class Parameter(val variableName: String, val type: ParameterEncoding, val grouped: Boolean)
+
+    enum class ParameterEncoding(val ionTextName: String) {
+        Tagged("any"),
+        // TODO: List all of the possible tagless encodings
+    }
+}
 
 /**
- * Represents a template macro. A template macro is defined by a name, a signature, and a list of template expressions.
+ * Represents a template macro. A template macro is defined by a signature, and a list of template expressions.
+ * A template macro only gains a name and/or ID when it is added to a macro table.
  */
-data class TemplateMacro(val name: String, val f: BigDecimal, val signature: MacroSignature, val body: List<TemplateExpression>) : Macro
+data class TemplateMacro(override val signature: List<Macro.Parameter>, val body: List<TemplateBodyExpression>) : Macro {
+    private val cachedHashCode by lazy { signature.hashCode() * 31 + body.hashCode() }
+    override fun hashCode(): Int = cachedHashCode
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other !is TemplateMacro) return false
+        // Check the hashCode as a quick check before we dive into the actual data.
+        if (cachedHashCode != other.cachedHashCode) return false
+        if (signature != other.signature) return false
+        if (body != other.body) return false
+        return true
+    }
+}
 
 /**
  * Macros that are built in, rather than being defined by a template.
  */
-enum class SystemMacro : Macro {
-    Stream, // A stream is technically not a macro, but we can implement it as a macro that is the identity function.
-    Annotate,
-    MakeString,
+enum class SystemMacro(override val signature: List<Macro.Parameter>) : Macro {
+    // TODO: replace these placeholders
+    Stream(emptyList()), // A stream is technically not a macro, but we can implement it as a macro that is the identity function.
+    Annotate(emptyList()),
+    MakeString(listOf(Macro.Parameter("text", Macro.ParameterEncoding.Tagged, grouped = true))),
     // TODO: Other system macros
 }

src/main/java/com/amazon/ion/impl/macro/MacroCompiler.kt

@@ -0,0 +1,240 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package com.amazon.ion.impl.macro
+
+import com.amazon.ion.*
+import com.amazon.ion.impl.macro.TemplateBodyExpression.*
+import com.amazon.ion.util.confirm
+
+/**
+ * [MacroCompiler] wraps an [IonReader]. When directed to do so, it will take over advancing and getting values from the
+ * reader in order to read one [TemplateMacro].
+ *
+ * This is currently implemented using [IonReader], but it could be adapted to work with
+ * [IonReaderContinuableCore][com.amazon.ion.impl.IonReaderContinuableCore].
+ */
+class MacroCompiler(private val reader: IonReader) {
+    // TODO: Make sure that we can throw exceptions if there's an over-sized value.
+
+    /** The name of the macro that was read. Returns `null` if no macro name is available. */
+    var macroName: String? = null
+        private set // Only mutable internally
+
+    private val signature: MutableList<Macro.Parameter> = mutableListOf()
+    private val expressions: MutableList<TemplateBodyExpression> = mutableListOf()
+
+    /**
+     * Compiles a template macro definition from the reader. Caller is responsible for positioning the reader at—but not
+     * stepped into—the macro template s-expression.
+     *
+     * TODO: if we switch the macro compiler to use a continuable reader, change the return type of this
+     *       to a compiler state enum, and add a separate function to get the compiled macro once it is ready.
+     */
+    fun compileMacro(): TemplateMacro {
+        macroName = null
+        signature.clear()
+        expressions.clear()
+
+        confirm(reader.type == IonType.SEXP) { "macro compilation expects a sexp starting with the keyword `macro`" }
+        reader.confirmNoAnnotations("a macro definition sexp")
+        reader.readContainer {
+            confirm(reader.next() == IonType.SYMBOL && reader.stringValue() == "macro") { "macro compilation expects a sexp starting with the keyword `macro`" }
+
+            nextAndCheckType(IonType.SYMBOL, "macro name")
+            confirmNoAnnotations("macro name")
+            // TODO: Enforce 'identifier' syntax subset of symbol
+            //       Possibly add support for macro definitions without names?
+            macroName = symbolValue().assumeText()
+
+            nextAndCheckType(IonType.SEXP, "macro signature")
+            confirmNoAnnotations("macro signature")
+            readSignature()
+
+            forEachRemaining { compileTemplateBodyExpression(isQuoted = false) }
+        }
+        return TemplateMacro(signature.toList(), expressions.toList())
+    }
+
+    /**
+     * Reads the macro signature, populating parameters in [signature].
+     * Caller is responsible for making sure that the reader is positioned on (but not stepped into) the signature sexp.
+     */
+    private fun readSignature() {
+        reader.forEachInContainer {
+            when (it) {
+                IonType.SYMBOL -> addParameter(grouped = false)
+                IonType.LIST -> {
+                    confirmNoAnnotations(location = "grouped parameter enclosing list")
+                    readContainer {
+                        nextAndCheckType(IonType.SYMBOL, "parameter name")
+                        addParameter(grouped = true)
+                        confirm(next() == null) { "grouped parameter list must enclose only one variable name" }
+                    }
+                }
+                else -> throw IonException("parameter must be a symbol or a list; found ${reader.type}")
+            }
+        }
+    }
+
+    /**
+     * Adds a parameter to the macro signature.
+     * Caller is responsible for making sure that the reader is positioned on a parameter name.
+     */
+    private fun addParameter(grouped: Boolean) {
+        val annotations = reader.typeAnnotations
+        confirm(annotations.isEmptyOr(Macro.ParameterEncoding.Tagged.ionTextName)) { "unsupported parameter encoding ${annotations.toList()}" }
+        val parameterName = reader.symbolValue().assumeText()
+        confirm(signature.none { it.variableName == parameterName }) { "redeclaration of parameter '$parameterName'" }
+        signature.add(Macro.Parameter(parameterName, Macro.ParameterEncoding.Tagged, grouped))
+    }
+
+    /**
+     * Compiles the current value on the reader into a [TemplateBodyExpression] and adds it to [expressions].
+     * Caller is responsible for ensuring that the reader is positioned on a value.
+     *
+     * If called when the reader is not positioned on any value, throws [IllegalStateException].
+     */
+    private fun compileTemplateBodyExpression(isQuoted: Boolean) {
+        // TODO: Could typeAnnotations ever be an array of nulls?
+        // NOTE: `toList()` does not allocate for an empty list.
+        val annotations = reader.typeAnnotationSymbols.toList()
+
+        if (reader.isNullValue) {
+            expressions.add(NullValue(annotations, reader.type))
+        } else when (reader.type) {
+            IonType.BOOL -> expressions.add(BoolValue(annotations, reader.booleanValue()))
+            IonType.INT -> expressions.add(
+                when (reader.integerSize!!) {
+                    IntegerSize.INT,
+                    IntegerSize.LONG -> IntValue(annotations, reader.longValue())
+                    IntegerSize.BIG_INTEGER -> BigIntValue(annotations, reader.bigIntegerValue())
+                }
+            )
+            IonType.FLOAT -> expressions.add(FloatValue(annotations, reader.doubleValue()))
+            IonType.DECIMAL -> expressions.add(DecimalValue(annotations, reader.decimalValue()))
+            IonType.TIMESTAMP -> expressions.add(TimestampValue(annotations, reader.timestampValue()))
+            IonType.STRING -> expressions.add(StringValue(annotations, reader.stringValue()))
+            IonType.BLOB -> expressions.add(BlobValue(annotations, reader.newBytes()))
+            IonType.CLOB -> expressions.add(ClobValue(annotations, reader.newBytes()))
+            IonType.SYMBOL -> {
+                if (isQuoted) {
+                    expressions.add(SymbolValue(annotations, reader.symbolValue()))
+                } else {
+                    val name = reader.stringValue()
+                    reader.confirmNoAnnotations("on variable reference '$name'")
+                    val index = signature.indexOfFirst { it.variableName == name }
+                    confirm(index >= 0) { "variable '$name' is not recognized" }
+                    expressions.add(Variable(index))
+                }
+            }
+            IonType.LIST -> compileSequence(isQuoted) { start, end -> ListValue(annotations, start, end) }
+            IonType.SEXP -> {
+                if (isQuoted) {
+                    compileSequence(isQuoted = true) { start, end -> SExpValue(annotations, start, end) }
+                } else {
+                    reader.confirmNoAnnotations(location = "a macro invocation")
+                    compileMacroInvocation()
+                }
+            }
+            IonType.STRUCT -> compileStruct(annotations, isQuoted)
+            // IonType.NULL, IonType.DATAGRAM, null
+            else -> TODO("Unreachable.")
+        }
+    }
+
+    /**
+     * Compiles a struct in a macro template.
+     * When calling, the reader should be positioned at the struct, but not stepped into it.
+     * If this function returns normally, it will be stepped out of the struct.
+     * Caller will need to call [IonReader.next] to get the next value.
+     */
+    private fun compileStruct(annotations: List<SymbolToken>, isQuoted: Boolean) {
+        val start = expressions.size
+        expressions.add(Placeholder)
+        val templateStructIndex = mutableMapOf<String, ArrayList<Int>>()
+        reader.forEachInContainer {
+            expressions.add(FieldName(fieldNameSymbol))
+            fieldNameSymbol.text?.let {
+                val valueIndex = expressions.size
+                // Default is an array list with capacity of 1, since the most common case is that a field name occurs once.
+                templateStructIndex.getOrPut(it) { ArrayList(1) } += valueIndex
+            }
+            compileTemplateBodyExpression(isQuoted)
+        }
+        val end = expressions.lastIndex
+        expressions[start] = StructValue(annotations, start, end, templateStructIndex)
+    }
+
+    /**
+     * Compiles a list or sexp in a macro template.
+     * When calling, the reader should be positioned at the sequence, but not stepped into it.
+     * If this function returns normally, it will be stepped out of the sequence.
+     * Caller will need to call [IonReader.next] to get the next value.
+     */
+    private inline fun compileSequence(isQuoted: Boolean, newTemplateBodySequence: (Int, Int) -> TemplateBodyExpression) {
+        val seqStart = expressions.size
+        expressions.add(Placeholder)
+        reader.forEachInContainer { compileTemplateBodyExpression(isQuoted) }
+        val seqEnd = expressions.lastIndex
+        expressions[seqStart] = newTemplateBodySequence(seqStart, seqEnd)
+    }
+
+    /**
+     * Compiles a macro invocation in a macro template.
+     * When calling, the reader should be positioned at the sexp, but not stepped into it.
+     * If this function returns normally, it will be stepped out of the sexp.
+     * Caller will need to call [IonReader.next] to get the next value.
+     */
+    private fun compileMacroInvocation() {
+        reader.stepIn()
+        val macroRef = when (reader.next()) {
+            IonType.SYMBOL -> {
+                val macroName = reader.stringValue()
+                // TODO: Once we have a macro table, validate name exists in current macro table.
+                if (macroName == "quote") null else MacroRef.ByName(macroName)
+            }
+            // TODO: When we have an ID for the macro "quote", add handling for it here.
+            // TODO: Once we have a macro table, validate that id exists in current macro table.
+            IonType.INT -> MacroRef.ById(reader.longValue())
+            else -> throw IonException("macro invocation must start with an id (int) or identifier (symbol); found ${reader.type ?: "nothing"}\"")
+        }
+
+        if (macroRef == null) {
+            // It's the "quote" macro; skip compiling a macro invocation and just treat all contents as literals
+            reader.forEachRemaining { compileTemplateBodyExpression(isQuoted = true) }
+        } else {
+            val macroStart = expressions.size
+            expressions.add(Placeholder)
+            reader.forEachRemaining { compileTemplateBodyExpression(isQuoted = false) }
+            val macroEnd = expressions.lastIndex
+            expressions[macroStart] =
+                MacroInvocation(macroRef, macroStart, macroEnd)
+        }
+        reader.stepOut()
+    }
+
+    // Helper functions
+
+    /** Utility method for checking that annotations are empty or a single array with the given annotations */
+    private fun Array<String>.isEmptyOr(text: String): Boolean = isEmpty() || (size == 1 && this[0] == text)
+
+    /** Throws [IonException] if any annotations are on the current value in this [IonReader]. */
+    private fun IonReader.confirmNoAnnotations(location: String) {
+        confirm(typeAnnotations.isEmpty()) { "found annotations on $location" }
+    }
+
+    /** Moves to the next type and throw [IonException] if it is not the `expected` [IonType]. */
+    private fun IonReader.nextAndCheckType(expected: IonType, location: String) {
+        confirm(next() == expected) { "$location must be a $expected; found ${type ?: "nothing"}" }
+    }
+
+    /** Steps into a container, executes [block], and steps out. */
+    private inline fun IonReader.readContainer(block: IonReader.() -> Unit) { stepIn(); block(); stepOut() }
+
+    /** Executes [block] for each remaining value at the current reader depth. */
+    private inline fun IonReader.forEachRemaining(block: IonReader.(IonType) -> Unit) { while (next() != null) { block(type) } }
+
+    /** Steps into a container, executes [block] for each value at that reader depth, and steps out. */
+    private inline fun IonReader.forEachInContainer(block: IonReader.(IonType) -> Unit) = readContainer { forEachRemaining(block) }
+}

src/main/java/com/amazon/ion/impl/macro/TemplateBodyExpression.kt

@@ -0,0 +1,81 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package com.amazon.ion.impl.macro
+
+import com.amazon.ion.IonType
+import com.amazon.ion.SymbolToken
+import com.amazon.ion.Timestamp
+import java.math.BigDecimal
+import java.math.BigInteger
+
+/**
+ * Represents an expression in the body of a template.
+ *
+ * We cannot use [`IonValue`](com.amazon.ion.IonValue) for this because `IonValue` requires references to parent
+ * containers and to an IonSystem which makes it impractical for reading and writing macros definitions. Furthermore,
+ * there is information we need to capture that cannot be expressed in the IonValue model, such as macro invocations
+ * and variable references.
+ *
+ * A template body is compiled into a list of expressions, without nesting, for ease and efficiency of evaluating
+ * e-expressions. Because of this, the container types do not have other values nested in them; rather they contain a
+ * range that indicates which of the following expressions are part of that container.
+ */
+sealed interface TemplateBodyExpression {
+    // TODO: Special Forms (if_void, for, ...)?
+
+    /**
+     * A temporary placeholder that is used only while a macro is partially compiled.
+     */
+    object Placeholder : TemplateBodyExpression
+
+    // Scalars
+    data class NullValue(val annotations: List<SymbolToken> = emptyList(), val type: IonType) : TemplateBodyExpression
+    data class BoolValue(val annotations: List<SymbolToken> = emptyList(), val value: Boolean) : TemplateBodyExpression
+    data class IntValue(val annotations: List<SymbolToken> = emptyList(), val value: Long) : TemplateBodyExpression
+    data class BigIntValue(val annotations: List<SymbolToken> = emptyList(), val value: BigInteger) : TemplateBodyExpression
+    data class FloatValue(val annotations: List<SymbolToken> = emptyList(), val value: Double) : TemplateBodyExpression
+    data class DecimalValue(val annotations: List<SymbolToken> = emptyList(), val value: BigDecimal) : TemplateBodyExpression
+    data class TimestampValue(val annotations: List<SymbolToken> = emptyList(), val value: Timestamp) : TemplateBodyExpression
+    data class StringValue(val annotations: List<SymbolToken> = emptyList(), val value: String) : TemplateBodyExpression
+    data class SymbolValue(val annotations: List<SymbolToken> = emptyList(), val value: SymbolToken) : TemplateBodyExpression
+    // We must override hashcode and equals in the lob types because `value` is a `byte[]`
+    data class BlobValue(val annotations: List<SymbolToken> = emptyList(), val value: ByteArray) : TemplateBodyExpression {
+        override fun hashCode(): Int = annotations.hashCode() * 31 + value.contentHashCode()
+        override fun equals(other: Any?): Boolean = other is BlobValue && annotations == other.annotations && value.contentEquals(other.value)
+    }
+    data class ClobValue(val annotations: List<SymbolToken> = emptyList(), val value: ByteArray) : TemplateBodyExpression {
+        override fun hashCode(): Int = annotations.hashCode() * 31 + value.contentHashCode()
+        override fun equals(other: Any?): Boolean = other is ClobValue && annotations == other.annotations && value.contentEquals(other.value)
+    }
+
+    /**
+     * An Ion List that could contain variables or macro invocations.
+     *
+     * @property startInclusive the index of the first expression of the list (i.e. this instance)
+     * @property endInclusive the index of the last expression contained in the list
+     */
+    data class ListValue(val annotations: List<SymbolToken> = emptyList(), val startInclusive: Int, val endInclusive: Int) : TemplateBodyExpression
+
+    /**
+     * An Ion SExp that could contain variables or macro invocations.
+     */
+    data class SExpValue(val annotations: List<SymbolToken> = emptyList(), val startInclusive: Int, val endInclusive: Int) : TemplateBodyExpression
+
+    /**
+     * An Ion Struct that could contain variables or macro invocations.
+     */
+    data class StructValue(val annotations: List<SymbolToken> = emptyList(), val startInclusive: Int, val endInclusive: Int, val templateStructIndex: Map<String, List<Int>>) : TemplateBodyExpression
+
+    data class FieldName(val value: SymbolToken) : TemplateBodyExpression
+
+    /**
+     * A reference to a variable that needs to be expanded.
+     */
+    data class Variable(val signatureIndex: Int) : TemplateBodyExpression
+
+    /**
+     * A macro invocation that needs to be expanded.
+     */
+    data class MacroInvocation(val macro: MacroRef, val startInclusive: Int, val endInclusive: Int) : TemplateBodyExpression
+}