SingleNamedColumnRowAdapter.kt

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package androidx.room.solver.query.result

import androidx.room.ext.L
import androidx.room.ext.RoomTypeNames
import androidx.room.ext.S
import androidx.room.ext.T
import androidx.room.ext.capitalize
import androidx.room.ext.stripNonJava
import androidx.room.solver.CodeGenScope
import androidx.room.solver.types.CursorValueReader
import androidx.room.vo.ColumnIndexVar
import com.squareup.javapoet.TypeName
import java.util.Locale

/**
 * Wraps a row adapter for a single item from a known column result.
 */
class SingleNamedColumnRowAdapter(
    val reader: CursorValueReader,
    val columnName: String,
) : QueryMappedRowAdapter(reader.typeMirror()) {
    override val mapping = SingleNamedColumnRowMapping(columnName)

    private val indexAdapter = object : IndexAdapter {

        private val indexVarNamePrefix =
            "_columnIndexOf${columnName.stripNonJava().capitalize(Locale.US)}"

        private lateinit var indexVarName: String

        override fun onCursorReady(cursorVarName: String, scope: CodeGenScope) {
            indexVarName = scope.getTmpVar(indexVarNamePrefix)
            scope.builder().addStatement(
                "final $T $L = $T.$L($L, $S)",
                TypeName.INT,
                indexVarName,
                RoomTypeNames.CURSOR_UTIL,
                "getColumnIndexOrThrow",
                cursorVarName,
                columnName
            )
        }

        override fun getIndexVars() = listOf(
            ColumnIndexVar(columnName, indexVarName)
        )
    }

    private lateinit var columnIndexVar: ColumnIndexVar

    override fun onCursorReady(
        indices: List<ColumnIndexVar>,
        cursorVarName: String,
        scope: CodeGenScope
    ) {
        columnIndexVar = indices.singleOrNull()
            ?: error("Expected a single resolved index var but got ${indices.size}")
    }

    override fun convert(outVarName: String, cursorVarName: String, scope: CodeGenScope) {
        reader.readFromCursor(outVarName, cursorVarName, columnIndexVar.indexVar, scope)
    }

    override fun getDefaultIndexAdapter() = indexAdapter

    data class SingleNamedColumnRowMapping(val usedColumn: String) : Mapping() {
        override val usedColumns = listOf(usedColumn)
    }
}