class BZgraflow extends Buildoz{

    constructor(){
        super()
        this.defaultAttrs = { tension: 100 }
        this.stagedNodes = { }
        this.stagedWires = { }
    }
    static _loadedNodeStyles = new Set() // Allow multi instances or re-loadNodes, but avoid reinjecting same styles !

    connectedCallback() { 
        super.connectedCallback()
        const flowUrl = this.getBZAttribute('flow')
        if(!flowUrl) {
            console.warn('BZgraflow: No flow URL !?')
            return
        }
        this.mainContainer  = document.createElement('div')
        this.mainContainer.classList.add('bzgf-main-container')
        this.shadow = this.mainContainer.attachShadow({ mode: 'open' })

        this.nodesContainer = document.createElement('div')
        this.nodesContainer.classList.add('bzgf-nodes-container')
        this.wiresContainer = document.createElementNS('http://www.w3.org/2000/svg', 'svg') 
        this.wiresContainer.setAttribute('overflow','visible')
        this.wiresContainer.classList.add('bzgf-wires-container')
        this.shadow.append(this.wiresContainer)
        this.shadow.append(this.nodesContainer)
        this.append(this.mainContainer)
        this.loadFlow(flowUrl) // Let it load async 
    }
    
    async loadFlow(url){
        const res = await fetch(url+'?'+crypto.randomUUID())
        const buf = await res.text()
        let flowObj
        try{
            flowObj = JSON.parse(buf)
        } catch(err){
            console.error('Could not parse flow JSON!?', err)
            return
        }
        if(!flowObj.nodesFile){
            console.error('No nodesFile in JSON!?')
            return
        }
        await this.loadNodes(flowObj.nodesFile)
        this.flow = flowObj.flow

        if(this.hasAnyLoop()) console.warn('This flow has loops.Optimization not available')
        this.refresh()
    }

    async loadNodes(url) {
        const res = await fetch(url+'?'+crypto.randomUUID())
        const html = await res.text()

        // Get nodes
        const doc = new DOMParser().parseFromString(html, 'text/html')
        this.nodesRegistry = {}
        for(const tpl of doc.querySelectorAll('template')){
            if(tpl.id=='svg-arrows'){
                this.wiresContainer.appendChild(tpl.querySelector('defs').cloneNode(true))
                this.arrowDefined = true
            } else {
                const rootEl = tpl.content.querySelector('.bzgf-node')
                if(!rootEl) continue
                this.nodesRegistry[rootEl.dataset.nodetype] = rootEl
            }
        }

        // Now load styles (once)
        if(!BZgraflow._loadedNodeStyles.has(url)) { 
            const styles = doc.querySelectorAll('style')
            styles.forEach(styleEl => {
                const style = document.createElement('style')
                style.textContent = styleEl.textContent
                this.shadow.appendChild(style)
            })
            BZgraflow._loadedNodeStyles.add(url)
        }
    }

    addNode(type, id, x, y){
        const nodeDef = this.nodesRegistry[type]
        this.stagedNodes[id] = nodeDef.cloneNode(true)
        const portEls = this.stagedNodes[id].querySelectorAll('.port')
        this.stagedNodes[id].style.left = `${x}px`
        this.stagedNodes[id].style.top = `${y}px`
        this.stagedNodes[id].dataset.id = id
        this.stagedNodes[id].ports = Object.fromEntries(Array.from(portEls).map(item => ([item.dataset.id, { ...item.dataset, el:item }])))
        this.nodesContainer.append(this.stagedNodes[id])
        return(this.stagedNodes[id])
    }

    addWire(link){
        const [idNode1, idPort1] = link.from
        const [idNode2, idPort2] = link.to
        const path = this.bezier(idNode1, idPort1, idNode2, idPort2, this.getBZAttribute('tension'))
        const id  = `${idNode1}_${idNode2}`
        this.stagedWires[id] = document.createElementNS('http://www.w3.org/2000/svg', 'path')
        this.stagedWires[id].setAttribute('d', path)
        this.stagedWires[id].setAttribute('fill', 'none')
        if(this.arrowDefined && link.endArrow) this.stagedWires[id].setAttribute('marker-end','url(#arrow)')
        if(this.arrowDefined && link.startArrow) this.stagedWires[id].setAttribute('marker-start','url(#arrow)')
        this.stagedWires[id].classList.add('bzgf-wire')
        this.stagedWires[id].dataset.id = id
        this.wiresContainer.append(this.stagedWires[id])
        return(this.stagedWires[id])
    }

    refresh(){
        let x = 0
        let y = 0
        for(const node of this.flow.nodes){
            const nodeEl = this.addNode(node.nodeType, node.id , node.coords.x, node.coords.y)
        } 
        for(const link of this.flow.links){
            this.addWire(link)
        }       
    }

    bezier(idNode1, idPort1, idNode2, idPort2, tensionMin=60) {
        const dirVect = {
            n: { x:  0, y: -1 },
            s: { x:  0, y:  1 },
            e: { x:  1, y:  0 },
            w: { x: -1, y:  0 },
        }
        const svgRect = this.wiresContainer.getBoundingClientRect()
        const node1 = this.stagedNodes[idNode1]
        const port1 = node1.ports[idPort1]
        const node2 = this.stagedNodes[idNode2]
        const port2 = node2.ports[idPort2]
        if(!node1 || !node2 || !port1 || !port2) {
            console.warn('bezier on bad node / port!', idNode1, idPort1, idNode2, idPort2)
            return('')
        }
        const bb1 = port1.el.getBoundingClientRect()
        const bb2 = port2.el.getBoundingClientRect()
        const x1 = Math.floor(bb1.x + (bb1.width/2)) - svgRect.left
        const y1 = Math.floor(bb1.y + (bb1.height/2)) - svgRect.top
        const x2 = Math.floor(bb2.x + (bb2.width/2)) - svgRect.left
        const y2 = Math.floor(bb2.y + (bb2.height/2)) - svgRect.top
        const dist = Math.abs(x2 - x1) + Math.abs(y2 - y1)
        let tension = dist * 0.4
        if(tension < tensionMin) tension = tensionMin

        const c1x = x1 + (dirVect[port1.direction].x * tension)
        const c1y = y1 + (dirVect[port1.direction].y * tension)

        const c2x = x2 + (dirVect[port2.direction].x * tension)
        const c2y = y2 + (dirVect[port2.direction].y * tension)
        return `M ${x1} ${y1} C ${c1x} ${c1y}, ${c2x} ${c2y}, ${x2} ${y2}`
    }

    autoPlace(orientation = 'horizontal', gapx = 80, gapy = 30){
        if(this.hasAnyLoop(this.flow.nodes, this.flow.links)){
            console.warn('Loop(s) detected... Cannot auto-place !')
            return
        }

        const parents = {}
        const adj = {}
        this.flow.nodes.forEach(n => {
            parents[n.id] = []
            adj[n.id] = []
        })

        this.flow.links.forEach(link => {
            const from = link.from[0]
            const to   = link.to[0]            
            parents[to].push(from)
            adj[from].push(to)
        })
    
        const layers = this.computeLayers(this.flow.nodes, parents)
        let maxHeight = 0; let maxWidth = 0
        const layerHeights = []; const layerWidths = []; 
        const indexes = {} // Todo: a
        for(const layer of layers){
            let totHeight = 0; let totWidth = 0
            for(const [idx, nid] of layer.entries()){
                const bb = this.stagedNodes[nid].getBoundingClientRect()
                totHeight += bb.height + gapy
                totWidth += bb.width + gapx
                indexes[nid] = idx 
            }
            if(totHeight>maxHeight) maxHeight = totHeight
            layerHeights.push(totHeight)
            if(totWidth>maxWidth) maxWidth = totWidth
            layerWidths.push(totWidth)
        }
        
        this.reorderLayers(layers, parents, indexes)

        if(orientation=='horizontal'){
            let x = gapx
            for(const [idx, layer] of layers.entries()){
                let wMax = 0
                let y = ((maxHeight - layerHeights[idx]) / 2) + gapy
                for(const nid of layer){
                    const bb = this.stagedNodes[nid].getBoundingClientRect()
                    wMax = (bb.width > wMax) ? bb.width : wMax
                    this.moveNode(nid, x, y, 1000)
                    y +=  gapy + bb.height
                }
                x += wMax + gapx
            }
        } else if(orientation=='vertical'){
            let y = gapy
            for(const [idx, layer] of layers.entries()){
                let hMax = 0
                let x = ((maxWidth - layerWidths[idx]) / 2) + gapx
                for(const nid of layer){
                    const bb = this.stagedNodes[nid].getBoundingClientRect()
                    hMax = (bb.height > hMax) ? bb.width : hMax
                    this.moveNode(nid, x, y, 1000)
                    x +=  gapx + bb.width
                }
                y += hMax + gapy
            }            
        }
    }

    reorderLayers(layers, parents, indexes){
        const swap = (vect, todo) => {
            for(const s of todo){
                [vect[s[0]], vect[s[1]]] = [vect[s[1]], vect[s[0]]]
            }
        }
        for(const [lidx, layer] of layers.entries()){
            if(lidx==0) continue
            const toSwap = []
            for(let i=0; i<layer.length; i++){
                const nid1 = layer[i]
                // some parents can be in far layers, but at least one is in the prev layer (by definition of layer)
                const pnid1 = parents[nid1].find((nid => layers[lidx-1].includes(nid)))
                for(let j=i+1; j<layer.length; j++){
                    const nid2 = layer[j]
                    const pnid2 = parents[nid2].find((nid => layers[lidx-1].includes(nid)))
                    if(((indexes[pnid1] - indexes[pnid2]) * (indexes[nid1] - indexes[nid2])) < 0) { // crossing !
                        toSwap.push([i, j])
                    }
                }
            }
            swap(layer, toSwap)
        }
    }

    moveNode(nid, destx, desty, duration = 200, cb) {
        const t0 = performance.now()
        const bb = this.stagedNodes[nid].getBoundingClientRect()
        const x0=bb.x
        const y0 = bb.y
        function frame(t) {
            const p = Math.min((t - t0) / duration, 1)
            const k = p * p * (3 - 2 * p) // smoothstep            
            const x = x0 + (destx - x0) * k
            const y = y0 + (desty - y0) * k
            
            this.stagedNodes[nid].style.left = `${x}px`
            this.stagedNodes[nid].style.top = `${y}px`
            this.updateWires(nid)
            
            if(p < 1) requestAnimationFrame(frame.bind(this))
        }    
        requestAnimationFrame(frame.bind(this))
    }

    updateWires(nid){
        const wires = Object.keys(this.stagedWires)
            .filter(id => (id.startsWith(nid+'_')||id.endsWith('_'+nid)))
            .map(id => this.stagedWires[id])
        for(const wire of wires){
            const [nid1, nid2] = wire.dataset.id.split('_')
            const lnk = this.getLink(nid1, nid2)
            const path = this.bezier(nid1, lnk.from[1], nid2, lnk.to[1], this.getBZAttribute('tension'))
            wire.setAttribute('d', path)
        }
    }

    getLink(nid1, nid2){
        return(this.flow.links.find(item => ((item.from[0]==nid1) && (item.to[0]==nid2))))
    }

    computeLayers(nodes, parents) {
        const layer = {}
        const dfs = (id) => {
            if (layer[id] !== undefined) return(layer[id])
            
            if (parents[id].length === 0) {
                layer[id] = 0
            } else {
                layer[id] = 1 + Math.max(...parents[id].map(dfs))
            }
            return(layer[id])
        }        
        nodes.forEach(n => dfs(n.id))
        const t = []
        for(const nid in layer) { 
            if(!t[layer[nid]]) t[layer[nid]]=[]
            t[layer[nid]].push(nid)
        } 
        return(t)
    }

    hasAnyLoop(nodes, links) {
        // self-loops
        if(this.flow.links.some(l => l.from[0] === l.to[0])) return(true)
        
        // multi-node cycles
        const adj = {};
        this.flow.nodes.forEach(node => adj[node.id] = [])
        this.flow.links.forEach(link => adj[link.from[0]].push(link.to[0])) 

        const visiting = new Set(); 
        const visited = new Set()
        const dfs = (nid) => {
            if(visiting.has(nid)) {
                return(true)
            }

            if(visited.has(nid)) return(false)
            visiting.add(nid)
            for(const m of adj[nid]) {
                if(dfs(m)) {
                    return(true)
                }
            }
            visiting.delete(nid)
            visited.add(nid)
            return(false)
        }    
        return(this.flow.nodes.map(n => n.id).some(dfs))
    }
    
}
Buildoz.define('graflow', BZgraflow)