zfs_backup_tool/tree.go

package main

import (
	"errors"
	"fmt"
)

/*
Frequency is a custom unit to represent the time intervals that snapshots are taken in.
*/
type frequency uint64

const yearly frequency = 0
const monthly frequency = 1
const weekly frequency = 2
const daily frequency = 3
const hourly frequency = 4
const frequent frequency = 5

/*
A snapshotTreeNode is a node in the tree representation of snapshots.
*/
type snapshotTreeNode struct {
	Data   Snapshot
	Before []snapshotTreeNode
	After  []snapshotTreeNode
}

/*
addSnapshot adds a snapshot into a tree
*/
func (node *snapshotTreeNode) addSnapshot(s Snapshot) (err error) {
	var tempNode snapshotTreeNode = snapshotTreeNode{Data: s}
	if node == nil {
		node = &tempNode
		return nil
	}
	if node.frequency() > s.frequency() {
		return fmt.Errorf("%s from a longer interval than %s", node.Data.String(), s.String())
	}
	if node.frequency() == s.frequency() {
		return fmt.Errorf("%s is from the same interval as %s", node.Data.String(), s.String())
	}
	if node.frequency() < s.frequency() {
		if node.frequency()+1 == s.frequency() {
			if node.Data.TimeStamp.After(s.TimeStamp) {
				if node.Before == nil {
					node.Before = append(node.Before, tempNode)
					return nil
				}
				var tSlice []snapshotTreeNode
				for index := 0; index < len(node.Before); index++ {
					if node.Before[index].Data.TimeStamp.Before(s.TimeStamp) {
						tSlice = append(tSlice, tempNode)
						copy(tSlice, node.Before[index:])
						break
					} else {
						tSlice = append(tSlice, node.Before[index])
					}
				}
				node.Before = tSlice
			}
			if node.Data.TimeStamp.Before(s.TimeStamp) {
				if node.After == nil {
					node.After = append(node.After, tempNode)
					return nil
				}
				var tSlice []snapshotTreeNode
				for index := 0; index < len(node.After); index++ {
					if node.After[index].Data.TimeStamp.Before(s.TimeStamp) {
						tSlice = append(tSlice, tempNode)
						copy(tSlice, node.After[index:])
						break
					} else {
						tSlice = append(tSlice, node.After[index])
					}
				}
				node.After = tSlice
			}
		} else {
			if node.Data.TimeStamp.After(s.TimeStamp) {
				for index := 0; index < len(node.Before); index++ {
					node.Before[index].Data.TimeStamp.Before(s.TimeStamp)
					node.Before[index].addSnapshot(s)
					break
				}
			}
		}
	}
	return errors.New("Non implemented branch in func (node * snapshotTreeNode) addSnapshot(s Snapshot)")
}

/*
The frequency of this snapshot's interval in the tree?
*/
func (node snapshotTreeNode) frequency() frequency {
	return node.Data.Interval
}