configure-pages/src/config-parser.js

import * as fs from "fs";
import * as espree from "espree";
import format from "string-format"

// Parse the AST
const espreeOptions = {
    ecmaVersion: 6,
    sourceType: "module",
    range: true,
}

export default class ConfigParser {
    
    constructor(staticSiteConfig){
        this.staticSiteConfig = staticSiteConfig
        this.config = fs.existsSync(this.staticSiteConfig.filePath) ? fs.readFileSync(this.staticSiteConfig.filePath, "utf8") : null
        this.validate()
    }

    validate(){
        if(!this.config){
            // Create the config file if it doesn't exist
            fs.writeFile(this.staticSiteConfig.filePath, this.generateConfigFile(), (err) => {
                  
                // In case of a error throw err.
                if (err) throw err;
            })
        }
    }

    pathPropertyNuxt = `router: {\n        base: '{0}'\n    }`
    pathPropertyNext = `basePath: '{0}'`
    pathPropertyGatsby = `pathPrefix: '{0}'`
    configskeleton = `export default {\n    {0}\n}`

    generateConfigFile(){
        switch(this.staticSiteConfig.type){
            case "nuxt":
            return format(this.configskeleton, format(this.pathPropertyNuxt, this.staticSiteConfig.newPath))
                break
            case "next":
                return format(this.configskeleton, format(this.pathPropertyNext, this.staticSiteConfig.newPath))
                break
            case "gatsby":
                return format(this.configskeleton, format(this.pathPropertyGatsby, this.staticSiteConfig.newPath))
                break
            default:
                throw "Unknown config type"
        }
    }

    generateConfigProperty(){
        switch(this.staticSiteConfig.type){
            case "nuxt":
                return format(this.pathPropertyNuxt, this.staticSiteConfig.newPath)
                break
            case "next":
                return format(this.pathPropertyNext, this.staticSiteConfig.newPath)
                break
            case "gatsby":
                return format(this.pathPropertyGatsby, this.staticSiteConfig.newPath)
                break
            default:
                throw "Unknown config type"
        }
    }

    parse(){
        const ast = espree.parse(this.config, espreeOptions);

        // Find the default export declaration node
        var exportNode = ast.body.find(node => node.type === 'ExpressionStatement')
        if (exportNode) {
            var property = this.getPropertyModuleExport(exportNode)

        } else {
            exportNode = ast.body.find(node => node.type === 'ExportDefaultDeclaration')
            if (!exportNode) throw "Unable to find default export"
            var property = this.getPropertyExportDefault(exportNode)
        }

        if(property){
            switch(this.staticSiteConfig.type){
            case "nuxt":
                this.parseNuxt(property)
                break
            case "next":
            case "gatsby":
                this.parseNextGatsby(property)
                    break
            default:
                throw "Unknown config type"
            }
        }
    }

    getPropertyModuleExport(exportNode){
        var propertyNode = exportNode.expression.right.properties.find(
            node => node.key.type === 'Identifier' && node.key.name === this.staticSiteConfig.pathName
            )

        if(!propertyNode){

            console.log( "Unable to find property, insert it :  " + this.staticSiteConfig.pathName)
            if(exportNode.expression.right.properties.length > 0){
                const newConfig = this.config.slice(0, exportNode.expression.right.properties[0].range[0]) + this.generateConfigProperty() + ',\n'  + this.config.slice(exportNode.expression.right.properties[0].range[0])
                console.log("new config = \n" + newConfig)
            } else {
                const newConfig = this.config.slice(0, exportNode.expression.right.range[0]+1) +  '\n    '+ this.generateConfigProperty() + '\n'  + this.config.slice(exportNode.expression.right.range[1]-1)
                console.log("new config = \n" + newConfig)
            }
        }
        return propertyNode
    }

    getPropertyExportDefault(exportNode){
        var propertyNode = exportNode.declaration.properties.find(
            node => node.key.type === 'Identifier' && node.key.name === this.staticSiteConfig.pathName
        )

        if(!propertyNode){

            console.log( "Unable to find property, insert it " + this.staticSiteConfig.pathName)
            if(exportNode.declaration.properties.length > 0){
                const newConfig = this.config.slice(0, exportNode.declaration.properties[0].range[0]) + this.generateConfigProperty() + ',\n'  + this.config.slice(exportNode.declaration.properties[0].range[0])
                console.log("new config = \n" + newConfig)
            } else {
                const newConfig = this.config.slice(0, exportNode.declaration.range[0]+1) +  '\n    '+ this.generateConfigProperty() + '\n'  + this.config.slice(exportNode.declaration.range[1]-1)
                console.log("new config = \n" + newConfig)
            }
        }

        return propertyNode
    }

    parseNuxt(propertyNode){
        // Find the base node
        if (propertyNode && propertyNode.value.type === 'ObjectExpression') {
            var baseNode = propertyNode.value.properties.find(node => node.key.type === 'Identifier' && node.key.name === this.staticSiteConfig.subPathName)//'base')
            if (baseNode) {
            console.log("base node = " + JSON.stringify(baseNode.value))

            // Swap the base value by a hardcoded string and print it
            const newConfig = this.config.slice(0, baseNode.value.range[0]) + `'${this.staticSiteConfig.newPath}'` + this.config.slice(baseNode.value.range[1])
            console.log("new config = \n" + newConfig)
            }
        }
    }

    parseNextGatsby(pathNode){
        if (pathNode) {
            console.log("base node = " + JSON.stringify(pathNode.value))

            const newConfig = this.config.slice(0, pathNode.value.range[0]) + `'${this.staticSiteConfig.newPath}'` + this.config.slice(pathNode.value.range[1])
            console.log("new config = \n" + newConfig)
        }
    }
}