PullDataFunctionHandler.kt

import org.javarosa.core.model.condition.EvaluationContext
import org.javarosa.core.model.condition.IFunctionHandler
import org.javarosa.xpath.XPathParseTool
import org.javarosa.xpath.expr.XPathExpression
import org.javarosa.xpath.expr.XPathFuncExpr

class PullDataFunctionHandler : IFunctionHandler {

    override fun getName(): String {
        return NAME
    }

    override fun getPrototypes(): List<Array<Class<Any>>> {
        return emptyList()
    }

    override fun rawArgs(): Boolean {
        return true
    }

    override fun realTime(): Boolean {
        return false
    }

    override fun eval(args: Array<Any>, ec: EvaluationContext): Any {
        val instanceId = XPathFuncExpr.toString(args[0])
        val child = XPathFuncExpr.toString(args[1])
        val filterChild = XPathFuncExpr.toString(args[2])
        val filterValue = XPathFuncExpr.toString(args[3])
        return createExpression(instanceId, child, filterChild, filterValue).eval(ec)
    }

    private fun createExpression(
        instanceId: String,
        child: String,
        filterChild: String,
        filterValue: String
    ): XPathExpression {
        return XPathParseTool.parseXPath(
            "instance('$instanceId')/root/item[$filterChild='$filterValue'][position() = 1]/$child"
        )
    }

    companion object {
        private const val NAME = "pulldata"
    }
}