// charts provides functions to create charts
// These are used to show statistics about users
// See userStatistics.go to see how input statistics are created

package createCharts

import "seekia/internal/statisticsDatum"

import goChart "github.com/wcharczuk/go-chart/v2"
import "github.com/wcharczuk/go-chart/v2/drawing"

import "image"
import "errors"

// Inputs:
//	-string: Chart title
//	-[]statisticsDatum.StatisticsDatum: Statistics datums list
//	-func(float64)(string, error): formatYAxisValuesFunction
//		-This will take values such as 1000000 and turn them to "1 million"
//	-bool: Y-axis units exist
//	-string: Y-axis units (example: " Users")
// Outputs:
//	-image.Image
//	-error
func CreateBarChart(chartTitle string, chartStatisticsDatumsList []statisticsDatum.StatisticsDatum, formatYAxisValuesFunction func(float64)(string, error), yAxisUnitsProvided bool, yAxisUnits string)(image.Image, error){

	if (len(chartStatisticsDatumsList) == 0) {
		return nil, errors.New("CreateBarChart called with empty chartStatisticsDatumsList")
	}

	chartDatumsList := make([]goChart.Value, 0, len(chartStatisticsDatumsList))

	for _, statisticsDatum := range chartStatisticsDatumsList{

		datumLabel := statisticsDatum.LabelFormatted

		datumValue := statisticsDatum.Value

		// We make sure this function does not error
		_, err := formatYAxisValuesFunction(datumValue)
		if (err != nil){
			return nil, errors.New("Invalid chartStatisticsDatumsList: Datum value is invalid. Reason: " + err.Error())
		}

		newChartValue := goChart.Value{
				Label: datumLabel,
				Value: datumValue,
			}

		chartDatumsList = append(chartDatumsList, newChartValue)
	}

	if (len(chartDatumsList) == 1){

		// This package cannot create bar charts with only 1 datum
		// Thus, we must add an empty datum

		newChartValue := goChart.Value{
				Style: goChart.Style{
					StrokeColor: drawing.ColorWhite,
					FillColor: drawing.ColorWhite,
				},
				Label: "",
				Value: .001,
			}

		chartDatumsList = append(chartDatumsList, newChartValue)
	}

	chartStyleObject := goChart.Style{
						Padding: goChart.Box{
							Top: 40,
							Bottom: 0,
							Left: 0,
							Right: 0,
							},
						}
	titleStyleObject := goChart.Style{
								Padding: goChart.Box{
									Top: 10,
									Bottom: 30,
								},
								FontSize: 15,
								FontColor: drawing.ColorBlack,
							}

	yAxisObject := goChart.YAxis{
			ValueFormatter: func(v interface{}) string {

				valueFloat64 := v.(float64)

				valueFormatted, err := formatYAxisValuesFunction(valueFloat64)
				if (err != nil){
					return "ERROR"
				}

				if (yAxisUnitsProvided == false){
					return valueFormatted
				}

				result := valueFormatted + yAxisUnits
				return result
			},
		}

	barChartObject := goChart.BarChart{
		Title: chartTitle,
		TitleStyle: titleStyleObject,
		Background: chartStyleObject,
		Height:   500,
		BarWidth: 60,
		Bars: chartDatumsList,
		YAxis: yAxisObject,
		}

	collector := &goChart.ImageWriter{}
	barChartObject.Render(goChart.PNG, collector)

	goImage, err := collector.Image()
	if (err != nil) { return nil, err }
	
	return goImage, nil
}

func CreateDonutChart(chartTitle string, chartStatisticsDatumsList []statisticsDatum.StatisticsDatum)(image.Image, error){

	if (len(chartStatisticsDatumsList) == 0) {

		return nil, errors.New("CreateDonutChart called with empty chartStatisticsDatumsList")
	}

	chartDatumsList := make([]goChart.Value, 0, len(chartStatisticsDatumsList))

	for _, statisticsDatum := range chartStatisticsDatumsList{

		datumLabel := statisticsDatum.LabelFormatted

		// Value is always a number representing the percentage of the donut
		datumValue := statisticsDatum.Value

		newChartValue := goChart.Value{
				Label: datumLabel,
				Value: datumValue,
			}

		chartDatumsList = append(chartDatumsList, newChartValue)
	}

	chartStyleObject := goChart.Style{
						Padding: goChart.Box{
							Top: 20,
							Bottom: 0,
							Left: 0,
							Right: 0,
							},
						}

	titleStyleObject := goChart.Style{
								FontSize: 15,
								FontColor: drawing.ColorBlack,
							}

	donutChartObject := goChart.DonutChart{
		Title: chartTitle,
		TitleStyle: titleStyleObject,
		Background: chartStyleObject,
		Height: 500,
		Values: chartDatumsList,
	}

	if (len(chartDatumsList) == 1){

		// Default is transparent, we need to add color
		sliceStyleObject := goChart.Style{
							FillColor: drawing.ColorRed,
						}
	
		donutChartObject.SliceStyle = sliceStyleObject
	}

	collector := &goChart.ImageWriter{}
	donutChartObject.Render(goChart.PNG, collector)

	goImage, err := collector.Image()
	if (err != nil) { return nil, err }
	
	return goImage, nil
}