// ==UserScript==
// @name         Pixiv save image with name format
// @namespace    https://blog.maple3142.net/
// @version      0.1
// @description  Save pixiv image with custom name format
// @author       maple3142
// @match        https://www.pixiv.net/member_illust.php?mode=medium&illust_id=*
// @connect      pximg.net
// @grant        unsafeWindow
// @grant        GM_xmlhttpRequest
// @downloadURL none
// ==/UserScript==

(function() {
    'use strict'
    const FILENAME_TEMPLATE='{{title}}-{{userName}}-{{id}}'

    const $=s=>document.querySelector(s)
    const $$=s=>[...document.querySelectorAll(s)]
    const elementmerge = (a , b ) => {
        Object.keys(b).forEach(k => {
            if (typeof b[k] === 'object') elementmerge(a[k], b[k])
            else if(k in a)a[k] = b[k]
            else a.setAttribute(k,b[k])
        })
    }
    const $el = (s, o) => {
        const el = document.createElement(s)
        elementmerge(el, o)
        return el
    }
    const debounce=delay=>fn=>{
        let de=false
        return (...args)=>{
            if(de)return
            de=true
            fn(...args)
            setTimeout(()=>(de=false),delay)
        }
    }
    const download=(url,fname)=>{
        const a=$el('a',{href:url,download:fname||true})
        document.body.appendChild(a)
        a.click()
        document.body.removeChild(a)
    }
    const gmxhr=o=>new Promise((res,rej)=>GM_xmlhttpRequest({...o,onload:res,onerror:rej}))

    function main(){
        const params=new URLSearchParams(location.search)
        const getIllustData=(id=params.get('illust_id'))=>fetch(`/ajax/illust/${id}`,{ credentials: 'same-origin' }).then(r=>r.json()).then(r=>r.body)
        const saveImage=(format=FILENAME_TEMPLATE,id=params.get('illust_id'))=>{
            getIllustData(id).then(data=>{
                const fname=format.replace(/{{(\w+?)}}/g,(m,g1)=>data[g1])
                const url=data.urls.original
                const ext=url.split('/').pop().split('.').pop()
                return Promise.all([fname+'.'+ext,gmxhr({method:'GET',url,responseType:'blob',headers:{Referer:'https://www.pixiv.net/'}})])
            }).then(([f,xhr])=>{
                const url=URL.createObjectURL(xhr.response)
                download(url,f)
                URL.revokeObjectURL(xhr.response)
            })
        }
        const observer=new MutationObserver(debounce(10)(mut=>{
            const menu=$('ul[role=menu]')
            if(!menu)return
            const n=menu.children.length
            const item=$el('li',{role:'menuitem',onclick:()=>saveImage()})
            item.className=menu.children[n-2].className
            const text=$el('span',{textContent:'⬇'})
            item.appendChild(text)
            menu.insertBefore(item,menu.children[n-1])
        }))
        const start=()=>observer.observe($('.sticky'),{childList:true,subtree:true})
        if(!$('.sticky'))setTimeout(start,1000)
        else start()
        if(!unsafeWindow.__$maple3142$_savePivivImage)Object.defineProperty(unsafeWindow,'__$maple3142$_savePivivImage',{
            get: ()=>saveImage,
            enumerable: false
        })
    }

    //ajax change
    let lasturl
    setInterval(()=>{
        if(location.href==lasturl)return
        lasturl=location.href
        main()
    },1000)
})()