/*
 * Wiki - A wiki with editor
 * Copyright (c) 2021-2021 Peter Stuifzand
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package main

import (
	"encoding/json"
	"os"
	"path/filepath"
	"strings"
)

type graphBuilder struct {
	refs      Refs
	nodeMap   NodeMap
	nodeCount int
	nodes     []Node
	edges     []Edge
}

type NodeMap map[string]Node

func NewGraphBuilder(mp PagesRepository) (*graphBuilder, error) {
	refs := make(Refs)

	f, err := os.Open(filepath.Join(mp.(*FilePages).dirname, "backrefs.json"))
	if err != nil {
		return nil, err
	}

	defer f.Close()

	err = json.NewDecoder(f).Decode(&refs)
	if err != nil {
		return nil, err
	}

	gb := &graphBuilder{
		refs:    refs,
		nodeMap: make(NodeMap),
		nodes:   nil,
		edges:   nil,
	}
	gb.nodeMap["Daily_Notes"] = Node{Id: -1}
	gb.nodeMap["TODO"] = Node{Id: -1}
	gb.nodeMap["DONE"] = Node{Id: -1}
	gb.nodeMap["Projects"] = Node{Id: -1}
	return gb, nil
}

func (gb *graphBuilder) prepareGraph() error {
	gb.nodes = prepareNodes(gb.nodeMap, func(node Node) Node {
		if node.Id == 0 {
			var green string
			green = "#f57900"
			node.Color = &green
		}
		return node
	})
	gb.edges = prepareEdges(gb.refs, gb.nodeMap)
	return nil
}

func (gb *graphBuilder) RemoveNode(name string) {
	delete(gb.nodeMap, name)
}

func (gb *graphBuilder) RemoveNodeWithSuffix(suffix string) {
	for k := range gb.nodeMap {
		if strings.HasSuffix(k, suffix) {
			delete(gb.nodeMap, k)
		}
	}
}

func (gb *graphBuilder) buildFromCenter(name string) error {
	id := gb.addNode(name, "#ef2929")
	if id < 0 {
		return nil
	}

	if ref, e := gb.refs[name]; e {
		for _, item := range ref {
			gb.addNode(item.Name, "#fce94f")
		}
	}

	for key, references := range gb.refs {
		for _, item := range references {
			if name == item.Name {
				gb.addNode(key, "#ad7fa8")
			}
		}
	}

	return nil
}

func prepareEdges(refs Refs, nodeMap NodeMap) []Edge {
	var edges []Edge
	edgeSet := make(map[Edge]bool)
	for key, references := range refs {
		if to, e := nodeMap[key]; e && to.Id >= 0 {
			for _, item := range references {
				if from, e := nodeMap[item.Name]; e && from.Id >= 0 {
					edge := Edge{
						From: from.Id,
						To:   to.Id,
					}
					if _, e := edgeSet[edge]; !e {
						edgeSet[edge] = true
						edges = append(edges, edge)
					}
				}
			}
		}
	}
	return edges
}

func prepareNodes(nodeMap NodeMap, apply func(node Node) Node) []Node {
	var nodes []Node
	for _, node := range nodeMap {
		if node.Id < 0 {
			continue
		}
		nodes = append(nodes, apply(Node{
			Id:      node.Id,
			Label:   node.Label,
			Title:   node.Title,
			Color:   node.Color,
			Opacity: node.Opacity,
		}))
	}
	return nodes
}

func (gb *graphBuilder) prepareNodeMap() {
	for key, references := range gb.refs {
		gb.addNode(key, "#5e8")
		for _, item := range references {
			gb.addNode(item.Name, "#403")
		}
	}
}

func (gb *graphBuilder) addNode(key string, color string) int {
	if _, e := gb.nodeMap[key]; !e {
		color := color
		title:= strings.Replace(key, "_", " ", -1)
		gb.nodeMap[key] = Node{gb.nodeCount, key, title, &color, 1}
		gb.nodeCount += 1
	}

	return gb.nodeMap[key].Id
}