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database.go
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587 lines (498 loc) · 9.87 KB
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package database
import (
"encoding/gob"
"fmt"
"log"
"os"
"time"
"github.com/gosimple/slug"
)
// Store is the main slice containing all the Posts
// var Store []Post
type Post struct {
Id int //'Unique' Key?
Title string
Content []byte
Slug string //slugified version of the title - for routing
PostDate time.Time
FeatureImg string
}
type Node struct {
Level int
Left *Node
Right *Node
Key int
Value string
}
type Tree struct {
Root *Node
}
var NilNode Node
func makeNilNode() *Node {
// Initialise Nil Node
NilNode.Level = 0
NilNode.Left = nil
NilNode.Right = nil
NilNode.Key = 0
NilNode.Value = ""
return &NilNode
}
func NewTree() *Tree {
t := new(Tree)
t.Root = &NilNode
return t
}
// NewNode creates a new node in the tree containing the key/value. Left and Right pointers are nil
func NewNode(key int, value string) *Node {
return &Node{1, nil, nil, key, value}
}
//Skew function
func Skew(n *Node) *Node {
if n.Left != nil {
if n.Level != 0 && n.Left.Level == n.Level {
// fmt.Println("Skew")
// var save = n.Left
// n.Left = save.Right
// save.Right = n
// n = save
//JS Skew
var temp = n
n = n.Left
temp.Left = n.Right
n.Right = temp
}
}
return n
}
// function split(node) {
// if (node.Right.Right.Level === node.Level) {
// var temp = node;
// node = node.Right;
// temp.Right = node.Left;
// node.Left = temp;
// node.Level++;
// }
// return node;
// }
// Split function
func Split(n *Node) *Node {
// time.Sleep(time.Second * 2)
if n.Right != nil && n.Right.Right != nil {
if n.Level != 0 && n.Right.Right.Level == n.Level {
// var save = n.Right
// n.Right = save.Left
// save.Left = n
// n = save
// n.Level++
//JS Split
var temp = n
n = n.Right
temp.Right = n.Left
n.Left = temp
n.Level++
}
}
return n
}
// Insert new item to the tree
func (tree *Tree) Insert(key int, value string) {
tree.Root = tree.Root.insert(key, value)
}
// Recursive insert
// func (n *Node) insert(key int, value string) *Node {
// if n == nil || n.Level == 0 {
// return NewNode(key, value)
// }
// if n.Value < value {
// n.Right = n.Right.insert(key, value)
// } else {
// n.Left = n.Left.insert(key, value)
// }
// n = Skew(n)
// n = Split(n)
// return n
// }
// Iterative Insert
func (n *Node) insert(key int, value string) *Node {
if n == nil || n.Level == 0 {
n = NewNode(key, value)
} else {
var save = n
var up []*Node
top := 0
dir := 0
for {
up = append(up, save)
if save.Value < value {
dir = 1
if save.Right == nil {
break
}
save = save.Right
} else {
dir = 0
if save.Left == nil {
break
}
save = save.Left
}
top++
}
if dir == 0 {
save.Left = NewNode(key, value)
} else {
save.Right = NewNode(key, value)
}
for i := top - 1; i >= 0; i-- {
if i != 0 {
if up[i-1].Right == up[i] {
dir = 1
} else {
dir = 0
}
}
up[i] = Split(Skew(up[i]))
if i != 0 {
if dir == 0 {
up[i-1].Left = up[i]
} else {
up[i-1].Right = up[i]
}
} else {
n = up[i]
}
}
}
return n
}
// Tree Remove
func (tree *Tree) Remove(value string) {
tree.Root = remove(tree.Root, value)
}
// Recursive Removal
// func remove(n *Node, value string) *Node {
// fmt.Println("remove", value)
// var heir *Node
// if n != nil {
// if n.Value == value {
// if n.Left != nil && n.Right != nil {
// heir = n.Left
// for heir.Right != nil {
// heir = heir.Right
// }
// n.Key = heir.Key
// n.Value = heir.Value
// n.Left = remove(n.Left, n.Value)
// } else if n.Left == nil {
// n = n.Right
// } else {
// n = n.Left
// }
// } else if n.Value < value {
// n.Right = remove(n.Right, value)
// } else {
// n.Left = remove(n.Left, value)
// }
// }
// if n.Left.Level < (n.Level-1) || n.Right.Level < (n.Level-1) {
// n.Level--
// if n.Right.Level > n.Level {
// n.Right.Level = n.Level
// }
// n = Split(Skew(n))
// }
// return n
// }
func remove(root *Node, value string) *Node {
if root != nil {
var it = root
var up []*Node
top := 0
dir := 0
dir2 := 0
for {
up = append(up, it)
if it == nil {
return root
} else if value == it.Value {
break
}
if it.Value < value {
dir = 1
it = it.Right
} else {
dir = 0
it = it.Left
}
top++
}
if it.Left == nil || it.Right == nil {
if it.Left == nil {
dir2 = 1
}
if top > 1 {
if dir == 0 {
if dir2 == 0 {
up[top-1].Left = it.Left
} else {
up[top-1].Left = it.Right
}
} else {
if dir2 == 0 {
up[top-1].Right = it.Left
} else {
up[top-1].Right = it.Right
}
}
} else {
root = it.Right
}
} else {
var heir = it.Right
var prev = it
for {
if heir.Left == nil {
break
}
up = append(up, prev)
heir = prev
heir = heir.Left
top++
}
it.Value = heir.Value
if prev == it {
prev.Right = heir.Right
} else {
prev.Left = heir.Right
}
}
for i := top - 1; i >= 0; i-- {
if i != 0 {
if up[i-1].Right == up[i] {
dir = 1
} else {
dir = 0
}
}
if up[i].Left.Level < up[i].Level-1 || up[i].Right.Level < up[i].Level-1 {
if up[i].Right.Level > up[i].Level-1 {
up[i].Right.Level = up[i].Level
}
up[i] = Skew(up[i])
up[i].Right = Skew(up[i].Right)
up[i].Right.Right = Skew(up[i].Right.Right)
up[i] = Split(up[i])
up[i].Right = Split(up[i].Right)
}
if i != 0 {
if dir == 0 {
up[i-1].Left = up[i]
} else {
up[i-1].Right = up[i]
}
} else {
root = up[i]
}
}
}
return root
}
// Tree Find
func (tree *Tree) Find(key int) string {
n := tree.Root
for n.Level != 0 {
if n.Key == key {
return n.Value
}
if n.Key < key {
n = n.Right
} else {
n = n.Left
}
}
return ""
}
// Traversing
// TREE TRAVERSAL
// Method on tree, returns a slice of keys which can be searched in store map
// Arguments
// reverse - bool, ascending = false, descending = true
// skip - int, number of items to skip from start of traversal
// limit - int, number of items to return from traversal
func (tree *Tree) InOrderTraversal(reverse bool, skip int, limit int) []int {
t := inorderTraversal(tree.Root, reverse, skip, limit)
return t
}
func inorderTraversal(n *Node, reverse bool, skip int, limit int) []int {
var res []int
cur := n
for cur != nil {
if cur.Left == nil {
res = append(res, cur.Key)
// if len(res) == l {
// return res
// }
cur = cur.Right
continue
}
pre := cur.Left
for pre.Right != nil && pre.Right != cur {
pre = pre.Right
}
if pre.Right == nil {
pre.Right = cur
cur = cur.Left
} else {
pre.Right = nil
res = append(res, cur.Key)
// if len(res) == l {
// return res
// }
cur = cur.Right
}
}
if reverse {
var reversed []int
for i := len(res) - 1; i >= 0; i-- {
reversed = append(reversed, res[i])
}
res = reversed
}
if skip != 0 {
var split []int
split = res[skip:]
res = split
if limit != 0 {
// var split []int
split = res[:limit]
res = split
}
}
if limit != 0 {
var split []int
split = res[:limit]
res = split
}
return res
}
var marker = "§"
type serialData struct {
Value string
index int
}
// SERIALIZING THE TREE
func (tree *Tree) Serialize() {
// If current node is NULL, store marker
var n = tree.Root
serialize(n)
}
func serialize(n *Node) {
if n == nil {
fmt.Print(marker)
return
}
// Else, store current node and recur for its children
fmt.Print(serialData{n.Value, n.Key})
serialize(n.Left)
serialize(n.Right)
}
// func DeSerialize(t *Tree, s string)
// {
// // Read next item from file. If theere are no more items or next
// // item is marker, then return
// int val;
// if !fscanf(fp, "%d ", &val) || val == MARKER {
// return
// }
// // Else create node with this item and recur for children
// root = newNode(val);
// DeSerialize(root->left, fp);
// DeSerialize(root->right, fp);
// }
//Database Map
type Store map[int]Post
func NewStore() Store {
return make(Store)
}
func LoadStore() {
f, err := os.OpenFile(file, os.O_RDWR|os.O_CREATE, 0755)
defer f.Close()
if err != nil {
log.Fatal(err)
}
fi, _ := f.Stat()
if err != nil {
// Could not obtain stat, handle error
}
if fi.Size() != 0 {
dec := gob.NewDecoder(f)
err = dec.Decode(&store)
if err != nil {
log.Fatal(err)
}
}
}
func BuildIndexes() {
for _, v := range store {
slugTree.Insert(v.Id, v.Slug)
dateTree.Insert(v.Id, v.PostDate.String())
}
}
func OpenAndIndex(f string) {
file = f
LoadStore()
BuildIndexes()
}
func AddToStore(title string, value []byte) {
// Generate key
key := len(store)
key++
// Date & Time
t := time.Now()
//Slugify
slug := slug.MakeLang(title, "en")
// Build the post struct
post := Post{}
post.Id = key
post.Title = title
post.Slug = slug
post.Content = value
post.PostDate = t
//Add to store
store[int(key)] = post
//Add to trees
slugTree.Insert(key, slug)
dateTree.Insert(key, time.Now().String())
//Persist to disk
f, err := os.OpenFile(file, os.O_RDWR|os.O_CREATE, 0755)
defer f.Close()
if err != nil {
log.Fatal(err)
}
enc := gob.NewEncoder(f)
err = enc.Encode(store)
if err != nil {
log.Fatal(err)
}
}
func GetRange(tree string, reverse bool, skip, limit int) []Post {
//lookup
var results []Post
var indexes []int
switch {
case tree == "date":
indexes = dateTree.InOrderTraversal(reverse, skip, limit)
case tree == "slug":
indexes = slugTree.InOrderTraversal(reverse, skip, limit)
}
// var indexes = tree.InOrderTraversal(reverse, skip, limit)
for _, v := range indexes {
results = append(results, store[v])
}
return results
}
//Global variables
var file string
var store = make(Store)
var slugTree = NewTree()
var dateTree = NewTree()