package geojson

import (
	"fmt"
	"strconv"
	"strings"
)

type CRS struct {
	Type       string            `json:"type"`
	Properties map[string]string `json:"properties,omitempty"`
}

func NewCRS(srid int) *CRS {
	properties := make(map[string]string)
	properties["name"] = fmt.Sprintf("EPSG:%d", srid)
	crs := &CRS{Type: "name", Properties: properties}
	return crs
}

func (c *CRS) SetSrid(srid int) {
	c.Type = "name"
	c.Properties = map[string]string{"name": fmt.Sprintf("EPSG:%d", srid)}
}

// GetSrid extracts the SRID from the CRS name and returns it as an integer.
func (c *CRS) GetSrid() (int, error) {
	if c.Type == "name" {
		if len(c.Properties) == 1 {
			for k, value := range c.Properties {
				if k == "name" {
					vv := strings.Split(value, ":")
					if len(vv) != 2 || !strings.EqualFold(vv[0], "EPSG") {
						return -1, fmt.Errorf("crs name is not in the format EPSG:<SRID>")
					}
					srid, err := strconv.Atoi(vv[1])
					if err != nil {
						return -1, fmt.Errorf("crs name is not a valid EPSG SRID")
					}
					return srid, nil
				}
			}
		}
	}
	return -1, fmt.Errorf("crs type is not 'name' or properties are not as expected")
}

// Verify checks if the crs is valid and returns true if it is, false otherwise and an error if there is a problem.
func (c *CRS) Verify() (bool, error) {
	srid, err := c.GetSrid()
	if err != nil {
		return false, err
	}
	if srid == -1 {
		return false, fmt.Errorf("crs is not valid")
	}
	return true, nil

}