gem-spaas-coding-challenge/spoptim/production_planner.go

package spoptim

import (
	"math"
	"sort"
	"encoding/json"

	"gem-spaas-coding-challenge/models"
)

var powerplantFuel = map[string]string{"gasfired": "gas(euro/MWh)", "turbojet": "kerosine(euro/MWh)", "windturbine": "wind(%)"}

func sliceSum(slice []float64) float64 {
	tot := 0.0
	for _, el := range slice {
		tot += el
	}
	return tot
}

func ProductionPlanner(payload *models.Payload) []interface{} {
	// handle empty payload
	if payload == nil {
		return make([]interface{}, 0)
	}

	// cast the fuels to map and validate
	fuels, _ := payload.Fuels.(map[string]interface{})
	for k := range powerplantFuel {
		if _, ok := fuels[powerplantFuel[k]]; !ok {
			res := make([]interface{}, 0)
			res = append(res, powerplantFuel[k] + " missing in Fuels") 
			return res
		}
	}

	// format wind plants for consistency with other types of plants
	wind, _ := fuels["wind(%)"].(json.Number).Float64()
	for _, plant := range payload.Powerplants {
		if *plant.Type == "windturbine" {
			*plant.Pmax = math.Round(*plant.Pmax * wind / 10) / 10
		}
	}
	fuels["wind(%)"] = json.Number(0)

	// order plants by merit
	sort.SliceStable(payload.Powerplants, func(i, j int) bool {
        fueli, _ := fuels[powerplantFuel[*payload.Powerplants[i].Type]].(json.Number).Float64()
        fuelj, _ := fuels[powerplantFuel[*payload.Powerplants[j].Type]].(json.Number).Float64()
        return fueli / *payload.Powerplants[i].Efficiency < fuelj / *payload.Powerplants[j].Efficiency
    })

	// Naively assign production by merit-order (with one check
	// to replace the last plant if too big pmin)
	load := 0.0
	cost := make([]float64, 0)
	res := make([]interface{}, 0)
	costToCompare := make([]interface{}, 0)
	resToCompare := make([][]interface{}, 0)
	for _, plant := range payload.Powerplants {
		remainingLoad := *payload.Load - load
		if remainingLoad == 0 {
			break
		}
		fuel, _ := fuels[powerplantFuel[*plant.Type]].(json.Number).Float64()
		if *plant.Pmin < remainingLoad {
			if *plant.Pmax != 0 {
				usedP := math.Min(remainingLoad, *plant.Pmax)
				load += usedP
				cost = append(cost, usedP / *plant.Efficiency * fuel)
				res = append(res, map[string]interface{}{
						"name": plant.Name,
						"p": usedP,
				})
			}
		} else {
			altRes := make([]interface{}, len(res))
			for i, re := range res {
				altRes[i] = map[string]interface{}{
					"name": re.(map[string]interface{})["name"],
					"p": re.(map[string]interface{})["p"],
				}
			}
			altCost := make([]float64, len(cost))
			copy(altCost, cost)
			loadToRemove := *plant.Pmin - remainingLoad
			for loadToRemove > 0 {
				if altRes[len(altRes)-1].(map[string]interface{})["p"].(float64) > loadToRemove {
					altCost[len(altCost)-1] = altCost[len(altCost)-1] * (1 - loadToRemove / altRes[len(altRes)-1].(map[string]interface{})["p"].(float64))
					altRes[len(altRes)-1].(map[string]interface{})["p"] = altRes[len(altRes)-1].(map[string]interface{})["p"].(float64) - loadToRemove
					loadToRemove = 0
				} else {
					loadToRemove = loadToRemove - altRes[len(altRes)-1].(map[string]interface{})["p"].(float64)
					altRes = altRes[:len(altRes)-1]
					altCost = altCost[:len(altRes)-1]
				}
			}
			altRes = append(altRes, map[string]interface{}{
					"name": *plant.Name,
					"p": *plant.Pmin,
			})
			altCost = append(altCost, *plant.Pmin / *plant.Efficiency * fuel)
			resToCompare = append(resToCompare, altRes)
			costToCompare = append(costToCompare, altCost)
		}
	}

	bestCost := sliceSum(cost)
	for i, altCost := range costToCompare {
		if sliceSum(altCost.([]float64)) < bestCost {
			bestCost = sliceSum(altCost.([]float64))
			res = resToCompare[i]
		}
	}

    return res
}