mirror of https://github.com/DanilaFe/abacus
30 lines
1.3 KiB
Kotlin
30 lines
1.3 KiB
Kotlin
package org.nwapw.abacus.context
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import org.nwapw.abacus.exception.ContextException
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import kotlin.reflect.KProperty
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/**
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* A delegate to search a hierarchy made up of [EvaluationContext].
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*
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* ChainSearchDelegate is a variable delegate written specifically for use in [EvaluationContext], because
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* of its hierarchical structure. Variables not found in the current context are searched
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* for in its parent, which continues recursively until the context being examined has no parent.
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* This class assists that logic, which is commonly re-used with different variable types, by calling
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* [valueGetter] on the current context, then its parent, etc.
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*
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* @param V the type of the property to search recursively.
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* @property valueGetter the getter lambda to access the value from the context.
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*/
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class ChainSearchDelegate<out V>(private val valueGetter: EvaluationContext.() -> V?) {
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operator fun getValue(selfRef: Any, property: KProperty<*>): V {
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var currentRef = selfRef as EvaluationContext
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var returnedValue = currentRef.valueGetter()
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while (returnedValue == null) {
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currentRef = currentRef.parent ?: break
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returnedValue = currentRef.valueGetter()
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}
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return returnedValue ?: throw ContextException("context chain does not contain value")
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}
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} |