const https = require('https')
const spawn = require('child_process').spawn
const exec  = require('child_process').exec

function download(url) {
    return new Promise((resolve,reject) => {
        https.get(url,(res) => {
            let data = ""
            res.on("data", (chunk) => data += chunk)
            res.on("end", () => resolve(data))
        }).on("error", (error) => reject(error))
    })
}

function section(title) {
    let border = '-'.repeat(8 + title.length)
    let middle = '--- ' + title + ' ---'
    console.log()
    console.log()
    console.log()
    console.log(border)
    console.log(middle)
    console.log(border)
    console.log()
}

async function with_cwd(dir,fn) {
    let cwd = process.cwd()
    process.chdir(dir)
    let out = await fn()
    process.chdir(cwd)
    return out
}

function run(cmd,args) {
    let out = ''
    return new Promise((resolve, reject) => {
        console.log(`Calling '${cmd} ${args.join(' ')}'`)
        let proc = spawn(cmd,args,{stdio:'inherit', shell:true})
        proc.on('exit', (code) => {
            if (code) process.exit(code)
            resolve(out)
        })
    })
}

function run_read(cmd,args) {
    let out = ''
    return new Promise((resolve, reject) => {
        let proc = spawn(cmd,args,{shell:true})
        proc.stderr.pipe(process.stderr)
        proc.stdout.on('data', (data) => { out += data })
        proc.on('exit', (code) => {
            if (code) process.exit(code);
            resolve(out)
        })
    })
}

async function check_version (name,required,cfg) {
    if (!cfg) { cfg = {} }
    let version = await run_read(name,['--version'])
    version     = version.trim()
    if (cfg.preprocess) { version = cfg.preprocess(version) }
    if (cfg.silent !== true) {
        console.log(`Checking if '${name}' version is '${required}'.`)
    }
    if (version != required) {
        throw `[ERROR] The '${name}' version '${version}' does not match the required one '${required}'.`
    }
}

async function get_npm_info (name) {
    let info = await run_read('npm',['info',name,'--json'])
    return JSON.parse(info)
}

async function get_npm_lts_version_of (name) {
    let info = await get_npm_info(name)
    version  = info['dist-tags'].lts
    return version
}

async function get_node_dist_index() {
    let index = await download('https://nodejs.org/dist/index.json')
    return JSON.parse(index)
}

async function get_node_lts_version() {
    let index = await get_node_dist_index()
    let newest = null
    for (let entry of index) {
        if (entry.lts !== false) {
            newest = entry
            break
        }
    }
    if (!newest) {
        throw "Cannot fetch the info about node LTS version."
    }
    let node = newest.version
    let npm  = newest.npm
    return [node,npm]
}

module.exports = {section,run,run_read,check_version,get_npm_info,get_npm_lts_version_of,with_cwd,
    get_node_dist_index,get_node_lts_version}