package org.example.web.report.jasper

import java.io.OutputStream
import java.util.Collection
import java.util.HashMap

import javax.servlet.http.HttpServletRequest
import javax.servlet.http.HttpServletResponse
import net.sf.jasperreports.engine.JRExporter
import net.sf.jasperreports.engine.JRExporterParameter
import net.sf.jasperreports.engine.JasperCompileManager
import net.sf.jasperreports.engine.JasperFillManager
import net.sf.jasperreports.engine.JasperPrint
import net.sf.jasperreports.engine.JasperReport
import net.sf.jasperreports.engine.data.JRBeanCollectionDataSource
import net.sf.jasperreports.engine.export.JRHtmlExporter
import net.sf.jasperreports.engine.export.JRHtmlExporterParameter
import net.sf.jasperreports.engine.export.JRPdfExporter
import net.sf.jasperreports.engine.export.JRXlsExporter
import net.sf.jasperreports.j2ee.servlets.BaseHttpServlet

object JasperReportGenerator {
  /**
   * Generates an Excel report using a specified report template and a
   * bean-collection data source for the report.
   *
   * @param reportPath Path to the JRXML file to use for generating the
   * report.
   * @param dataSource A {@link Collection} of objects to use as the
   * data source for the report.
   * @param response The {@link HttpServletResponse} to which the report
   * should be written.
   */
  def generateExcel(reportPath: String, dataSource: Collection[_], response: HttpServletResponse) {
    this.generate(reportPath, dataSource, new JRXlsExporter, None, response, Some("application/vnd.ms-excel"))
  }

  /**
   * Generates an HTML report using a specified report template and a
   * bean-collection data source for the report.
   *
   * @param reportPath Path to the JRXML file to use for generating the
   * report.
   * @param dataSource A {@link Collection} of objects to use as the
   * data source for the report.
   * @param request The current {@link HttpServletRequest}.
   * @param response The {@link HttpServletResponse} to which the report
   * should be written.
   */
  def generateHTML(reportPath: String, dataSource: Collection[_], request: HttpServletRequest, response: HttpServletResponse) {
    this.generate(reportPath, dataSource, new JRHtmlExporter, Some(request), response)
  }

  /**
   * Generates a PDF report using a specified report template and a
   * bean-collection data source for the report.
   *
   * @param reportPath Path to the JRXML file to use for generating the
   * report.
   * @param dataSource A {@link Collection} of objects to use as the
   * data source for the report.
   * @param response The {@link HttpServletResponse} to which the report
   * should be written.
   */
  def generatePDF(reportPath: String, dataSource: Collection[_], response: HttpServletResponse) {
    this.generate(reportPath, dataSource, new JRPdfExporter, None, response, Some("application/pdf"))
  }

  /**
   * Generates a compiled report using a specified report template and a
   * collection data source for the report.
   *
   * @param reportPath Path to the JRXML file to use for generating the
   * report.
   * @param dataSource A {@link Collection} of objects to use as the
   * data source for the report.
   * @param exporter A {@link JRExporter} to use to generate the report.
   * @param request The current {@link HttpServletRequest}.
   * @param response The {@link HttpServletResponse} to which the report
   * should be written.
   * @param contentType The HTTP response content type for the report.
   */
  private def generate(reportPath: String, dataSource: Collection[_], exporter: JRExporter, request: Option[HttpServletRequest], response: HttpServletResponse, contentType: Option[String] = None) {
    val output = response.getOutputStream

    try {
      this.prepare(this.print(JasperCompileManager.compileReport(this.load(reportPath)), dataSource), exporter, request, output)

      exporter.exportReport()

      contentType match {
        case Some(s) => response.setContentType(s)
        case _ =>
      }

      output.flush()
    } finally {
      output.close()
    }
  }

  /**
   * Loads a JRXML report template.
   *
   * @param reportPath Path to the JRXML file to load.
   * @return An {@link InputStream} that can be used to read the JRXML
   * report template.
   */
  private def load(reportPath: String) = this.getClass.getClassLoader.getResourceAsStream(reportPath)

  /**
   * Prepares to generate a report.
   *
   * @param print The report to prepare
   * @param exporter The exporter to use.
   * @param request The current {@link HttpServletRequest}.
   * @param output The {@link OutputStream} to which the report must be written.
   */
  private def prepare(print: JasperPrint, exporter: JRExporter, request: Option[HttpServletRequest], output: OutputStream) {
    request match {
      case Some(request) =>
        // Add the compiled report to the HTTP Session because any graphics
        // embedded in the report are generated by a Servlet that is invoked
        // after the web page has been rendered.
        request.getSession.setAttribute(BaseHttpServlet.DEFAULT_JASPER_PRINT_SESSION_ATTRIBUTE, print)

      case None =>
    }

    exporter.setParameter(JRExporterParameter.JASPER_PRINT, print)
    exporter.setParameter(JRExporterParameter.OUTPUT_STREAM, output)
    exporter.setParameter(JRHtmlExporterParameter.IMAGES_URI, "/report/graphics?image=")
    exporter.setParameter(JRHtmlExporterParameter.IS_USING_IMAGES_TO_ALIGN, false)

    exporter.exportReport()
  }

  /**
   * Merges a compiled report with data.
   *
   * @param report The compiled report to merge.
   * @param dataSource A {@link Collection} of objects to merge.
   * @return A {@link JasperPrint}.
   */
  private def print(report: JasperReport, dataSource: Collection[_]) = JasperFillManager.fillReport(report, new HashMap[String, Object], new JRBeanCollectionDataSource(dataSource))
}