LLKennedy/imagetemplate

// Package circle is a simple circle component with customisable size, colour, location and radius.
package circle

import (
    "fmt"
    "image"
    "image/color"

    "github.com/LLKennedy/imagetemplate/v3/cutils"
    "github.com/LLKennedy/imagetemplate/v3/render"
    "golang.org/x/tools/godoc/vfs"
)

// Component implements the Component interface for circles.
type Component struct {
    /*
        NamedPropertiesMap maps user/application variables to properties of the component.
        This field is filled automatically by VerifyAndSetJSONData, then used in
        SetNamedProperties to determine whether a variable being passed in is relevant to this
        component.

        For example, map[string][]string{"circleSize": []string{"radius"}} would indicate that
        the user specified variable "circleSize" will fill the Radius property.
    */
    NamedPropertiesMap map[string][]string
    /*
        Centre is the coordinates of the centre of the circle relative to the top-left corner
        of the canvas.
    */
    Centre image.Point
    // Radius is the radius of the circle.
    Radius int
    // Colour is the colour of the circle.
    Colour color.NRGBA
}

type circleFormat struct {
    CentreX string       `json:"centreX"`
    CentreY string       `json:"centreY"`
    Radius  string       `json:"radius"`
    Colour  colourFormat `json:"colour"`
}

type colourFormat struct {
    Red   string `json:"R"`
    Green string `json:"G"`
    Blue  string `json:"B"`
    Alpha string `json:"A"`
}

// Write draws a circle on the canvas.
func (component Component) Write(canvas render.Canvas) (render.Canvas, error) {
    if len(component.NamedPropertiesMap) != 0 {
        return canvas, fmt.Errorf("cannot draw circle, not all named properties are set: %v", component.NamedPropertiesMap)
    }
    return canvas.Circle(component.Centre, component.Radius, component.Colour)
}

// SetNamedProperties processes the named properties and sets them into the circle properties.
func (component Component) SetNamedProperties(properties render.NamedProperties) (render.Component, error) {
    c := component
    var err error
    c.NamedPropertiesMap, err = render.StandardSetNamedProperties(properties, component.NamedPropertiesMap, (&c).delegatedSetProperties)
    if err != nil {
        return component, err
    }
    return c, nil
}

// GetJSONFormat returns the JSON structure of a circle component.
func (component Component) GetJSONFormat() interface{} {
    return &circleFormat{}
}

// VerifyAndSetJSONData processes the data parsed from JSON and uses it to set circle properties and fill the named properties map.
func (component Component) VerifyAndSetJSONData(data interface{}) (render.Component, render.NamedProperties, error) {
    c := component
    props := make(render.NamedProperties)
    stringStruct, ok := data.(*circleFormat)
    if !ok {
        return component, props, fmt.Errorf("failed to convert returned data to component properties")
    }
    // Get named properties and assign each real property
    var newVal interface{}
    var err error
    c.Centre.X, c.NamedPropertiesMap, err = cutils.ExtractInt(stringStruct.CentreX, "centreX", c.NamedPropertiesMap)
    if err != nil {
        return component, props, err
    }
    c.Centre.Y, c.NamedPropertiesMap, err = cutils.ExtractInt(stringStruct.CentreY, "centreY", c.NamedPropertiesMap)
    if err != nil {
        return component, props, err
    }
    c.Radius, c.NamedPropertiesMap, err = cutils.ExtractInt(stringStruct.Radius, "radius", c.NamedPropertiesMap)
    if err != nil {
        return component, props, err
    }
    c.NamedPropertiesMap, newVal, err = render.ExtractSingleProp(stringStruct.Colour.Red, "R", render.Uint8Type, c.NamedPropertiesMap)
    if err != nil {
        return component, props, err
    }
    if newVal != nil {
        c.Colour.R = newVal.(uint8)
    }
    c.NamedPropertiesMap, newVal, err = render.ExtractSingleProp(stringStruct.Colour.Green, "G", render.Uint8Type, c.NamedPropertiesMap)
    if err != nil {
        return component, props, err
    }
    if newVal != nil {
        c.Colour.G = newVal.(uint8)
    }
    c.NamedPropertiesMap, newVal, err = render.ExtractSingleProp(stringStruct.Colour.Blue, "B", render.Uint8Type, c.NamedPropertiesMap)
    if err != nil {
        return component, props, err
    }
    if newVal != nil {
        c.Colour.B = newVal.(uint8)
    }
    c.NamedPropertiesMap, newVal, err = render.ExtractSingleProp(stringStruct.Colour.Alpha, "A", render.Uint8Type, c.NamedPropertiesMap)
    if err != nil {
        return component, props, err
    }
    if newVal != nil {
        c.Colour.A = newVal.(uint8)
    }
    for key := range c.NamedPropertiesMap {
        props[key] = struct {
            Message string
        }{Message: "Please replace me with real data"}
    }
    return c, props, nil
}

func init() {
    for _, name := range []string{"circle", "Circle", "CIRCLE"} {
        render.RegisterComponent(name, func(vfs.FileSystem) render.Component { return Component{} })
    }
}