// Copyright (C) 2020 Marius Schellenberger

package pve

import (
	"context"
	"errors"
	"fmt"
	"sort"
)

var (
	ErrNodesOffline        = errors.New("one or more nodes are offline")
	ErrNodesNotSearched    = errors.New("one or more nodes could not be searched")
	ErrUnschedulable       = errors.New("no schedulable node found")
	ErrTooManyServersFound = errors.New("too many servers found with the same name")
)

type NodeStatus string

const (
	NodeStatusOnline  NodeStatus = "online"
	NodeStatusOffline NodeStatus = "offline"
	NodeStatusUnknown NodeStatus = "unknown"
)

type Node struct {
	Name       string        `json:"node"`
	Status     NodeStatus    `json:"status"`
	CPU        float64       `json:"cpu"`
	MaxCPU     float64       `json:"maxcpu"`
	Mem        uint64        `json:"mem"`
	MaxMem     uint64        `json:"maxmem"`
	Disk       uint64        `json:"disk"`
	MaxDisk    uint64        `json:"maxdisk"`
	serverList ServerRefList `json:"-"`
}

func (n *Node) memFreePercent() float64 {
	return float64(n.Mem) / float64(n.MaxMem) * 100
}

func (n *Node) memUsedPercent() float64 {
	return float64(n.MaxMem-n.Mem) / float64(n.MaxMem) * 100
}

func (n *Node) weight() int {
	return int(n.memUsedPercent()) + (len(n.serverList) * 10)
}

type NodeList []*Node

func (nl NodeList) sortByWeight() {
	sort.Sort(weightSorter(nl))
}

func (nl *NodeList) remove(i int) {
	(*nl)[i] = (*nl)[len(*nl)-1]
	*nl = (*nl)[:len(*nl)-1]
}

func (nl *NodeList) filter(filters ...NodeFilter) {
	for _, f := range filters {
		f(nl)
	}
}

func (nl *NodeList) getServerList(ctx context.Context, c *NodeClient) (err error) {
	for _, n := range *nl {
		n.serverList, err = c.ListServers(ctx, n)
		if err != nil {
			return
		}
	}
	return
}

type weightSorter NodeList

func (s weightSorter) Len() int { return len(s) }
func (s weightSorter) Less(i, j int) bool {
	return s[i].weight() < s[j].weight()
}
func (s weightSorter) Swap(i, j int) { s[i], s[j] = s[j], s[i] }

type NodeFilter func(*NodeList)

func FilterOnlineNode() NodeFilter {
	return func(nl *NodeList) {
		for i, n := range *nl {
			if n.Status != NodeStatusOnline {
				nl.remove(i)
			}
		}
	}
}

func FilterNodeName(name string) NodeFilter {
	return func(nl *NodeList) {
		for i, n := range *nl {
			if n.Name == name {
				nl.remove(i)
				return
			}
		}
	}
}

func FilterMaxCores(cores uint64) NodeFilter {
	return func(nl *NodeList) {
		for i, n := range *nl {
			if cores > uint64(n.MaxCPU) {
				nl.remove(i)
			}
		}
	}
}

const (
	mib = 1024 * 1024
	gib = mib * 1024
)

func FilterFreeMem(mem uint64) NodeFilter {
	return func(nl *NodeList) {
		for i, n := range *nl {
			if (mem * gib) >= n.MaxMem-n.Mem {
				nl.remove(i)
			}
		}
	}
}

// Useful? only local disk?
func FilterFreeDisk(disk uint64) NodeFilter {
	return func(nl *NodeList) {
		for i, n := range *nl {
			if (disk * gib) >= n.MaxDisk-n.Disk {
				nl.remove(i)
			}
		}
	}
}

func FilterVMAntiAffinity(url string) NodeFilter {
	return func(nl *NodeList) {
		_, _, id, err := ParseURL(url)
		if err != nil {
			return
		}
		for i, n := range *nl {
			for _, s := range n.serverList {
				if s.ID == id {
					nl.remove(i)
					return
				}
			}
		}
	}
}

type NodeClient struct {
	client *Client
}

func (c *NodeClient) Schedule(ctx context.Context, filters ...NodeFilter) (n *Node, err error) {
	nl, err := c.List(ctx)
	if err != nil {
		return
	}
	err = nl.getServerList(ctx, c)
	if err != nil {
		return
	}
	nl.filter(filters...)
	nl.sortByWeight()
	if len(nl) == 0 {
		err = ErrUnschedulable
		return
	}
	n = nl[0]
	return
}

func (c *NodeClient) List(ctx context.Context) (nl NodeList, err error) {
	req, err := c.client.NewRequest(ctx, "GET", "/nodes", nil)
	if err != nil {
		return
	}
	_, err = c.client.Do(req, &nl)
	return
}

func (c *NodeClient) ListServers(ctx context.Context, n *Node) (sl ServerRefList, err error) {
	req, err := c.client.NewRequest(ctx, "GET", fmt.Sprintf("/nodes/%s/qemu", n.Name), nil)
	if err != nil {
		return
	}
	_, err = c.client.Do(req, &sl)
	if err == nil {
		for i := range sl {
			sl[i].Node = n.Name
		}
	}
	return
}

func (c *NodeClient) FindServer(ctx context.Context, name string, id int) (ref *ServerRef, err error) {
	valid := ValidateID(id) == nil
	nl, err := c.List(ctx)
	if err != nil {
		return
	}
	var (
		nodeOffline     bool
		nodeNotSearched bool
	)
	for _, node := range nl {
		if node.Status != NodeStatusOnline {
			nodeOffline = true
			continue
		}
		sl, err := c.ListServers(ctx, node)
		if err != nil {
			nodeNotSearched = true
			continue
		}
		for _, s := range sl {
			if valid && s.ID == id {
				return s, nil
			}
			if name != "" && s.Name == name {
				if ref != nil {
					return nil, ErrTooManyServersFound
				}
				ref = s
			}
		}
	}
	if nodeOffline {
		return nil, ErrNodesOffline
	}
	if nodeNotSearched {
		return nil, ErrNodesNotSearched
	}
	if ref == nil {
		err = ErrServerNotFound
	}
	return
}

func (c *NodeClient) FindServerByName(ctx context.Context, name string) (s *ServerRef, err error) {
	return c.FindServer(ctx, name, InvalidID)
}

func (c *NodeClient) FindServerByID(ctx context.Context, id int) (s *ServerRef, err error) {
	err = ValidateID(id)
	if err != nil {
		return
	}
	return c.FindServer(ctx, "", id)
}

func (c *NodeClient) FindServerByURL(ctx context.Context, url string) (s *ServerRef, err error) {
	_, _, id, err := ParseURL(url)
	if err != nil {
		return
	}
	return c.FindServerByID(ctx, id)
}