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package cdc.impex.exports;

import java.util.Map;
import java.util.function.Function;

import cdc.impex.templates.SheetTemplateInstance;
import cdc.issues.Issue;
import cdc.issues.IssuesHandler;
import cdc.util.lang.Checks;

/**
 * Interface implemented by classes that can extract workbook data to export.
 *
 * @author Damien Carbonne
 */
public interface WorkbookExporter extends SheetExporter {
    public static final WorkbookExporter QUIET_VOID = new CheckedWorkbookExporter();
    public static final WorkbookExporter VERBOSE_VOID = new VerboseWorkbookExporter(QUIET_VOID);

    /**
     * Invoked to notify the beginning of export.
     *
     * @param issuesHandler The issues handler that should be used by the application to
     *            generate new issues.
     */
    public default void beginExport(IssuesHandler issuesHandler) {
        // Ignore
    }

    /**
     * Invoked to notify the end of export.
     *
     * @param issuesHandler The issues handler that should be used by the application to
     *            generate new issues.
     */
    public default void endExport(IssuesHandler issuesHandler) {
        // Ignore
    }

    /**
     * Creates a delegating workbook exporter.
     * 
     * When the export of a sheet starts, an appropriate sheet exporter is selected,
     * if possible, among {@code delegates}.
     * If no appropriate sheet exporter is found, the default workbook exporter is used. The default will usually ignore things.
     *
     * @param def The default workbook exporter.

     *            It can be {@link #QUIET_VOID}, {@link #VERBOSE_VOID},
     *            or any other valid WorkbookExporter.
     * @param function The function that maps template names to the associated sheet exporters.
     * @return A new WorkbookExporter that delegates export if possible, or use the default workbook exporter otherwise.
     */
    public static WorkbookExporter fromDelegates(WorkbookExporter def,
                                                 Function function) {
        Checks.isNotNull(def, "def");
        Checks.isNotNull(function, "function");

        return new WorkbookExporter() {
            private SheetExporter delegate = null;

            private SheetExporter get() {
                return delegate == null ? def : delegate;
            }

            @Override
            public void beginExport(IssuesHandler issuesHandler) {
                def.beginExport(issuesHandler);
            }

            @Override
            public void beginSheetExport(SheetTemplateInstance templateInstance,
                                         IssuesHandler issuesHandler) {
                delegate = function.apply(templateInstance.getTemplate().getName());
                get().beginSheetExport(templateInstance, issuesHandler);
            }

            @Override
            public int getNumberOfRemainingRows() {
                return get().getNumberOfRemainingRows();
            }

            @Override
            public void exportRow(ExportRow row,
                                  IssuesHandler issuesHandler) {
                get().exportRow(row, issuesHandler);
            }

            @Override
            public void endSheetExport(SheetTemplateInstance templateInstance,
                                       IssuesHandler issuesHandler) {
                get().endSheetExport(templateInstance, issuesHandler);
            }

            @Override
            public void endExport(IssuesHandler issuesHandler) {
                def.endExport(issuesHandler);
            }
        };
    }

    public static WorkbookExporter fromDelegates(Function function) {
        return fromDelegates(QUIET_VOID, function);
    }

    /**
     * Creates a delegating workbook exporter.
     *
     * @param def The default workbook exporter.

     *            It can be {@link #QUIET_VOID}, {@link #VERBOSE_VOID},
     *            or any other valid WorkbookExporter.
     * @param map The map from template names to the associated sheet exporters.
     * @return A new WorkbookExporter that delegates export if possible, or use the default workbook exporter otherwise.
     */
    public static WorkbookExporter fromDelegates(WorkbookExporter def,
                                                 Map map) {
        return fromDelegates(def, map::get);
    }

    public static WorkbookExporter fromDelegates(Map map) {
        return fromDelegates(map::get);
    }
}