/*
* @Author: Bartuccio Antoine
* @Date:   2018-07-24 01:27:11
* @Last Modified by:   klmp200
* @Last Modified time: 2018-07-24 11:51:52
 */

package shared

import (
	"sync"
)

type history struct {
	mutex sync.Mutex
	size  int
	data  map[int64][]string
}

var History history

// Init a chat history of a given size
func InitHistory(size int) {
	History = history{}
	History.mutex.Lock()
	defer History.mutex.Unlock()
	History.size = size
	History.data = make(map[int64][]string)
}

// Get the number of messages saved in the history
func (h history) Size() int {
	h.mutex.Lock()
	defer h.mutex.Unlock()
	return h.size
}

// Get a selected message in a chat history
func (h history) Message(chatID int64, n int) string {
	h.mutex.Lock()
	defer h.mutex.Unlock()
	array, exists := h.data[chatID]
	if exists && n >= 0 && n < len(array) {
		return array[n]
	}
	return ""
}

// Append a message to a given chat
func (h history) AddMessage(chatID int64, m string) {
	h.mutex.Lock()
	defer h.mutex.Unlock()
	if _, exists := h.data[chatID]; !exists {
		h.data[chatID] = make([]string, h.size, h.size)
	}
	h.append(chatID, m)
}

// Get the last message of a given chat
func (h history) LastMessage(chatID int64) string {
	h.mutex.Lock()
	defer h.mutex.Unlock()
	if _, exists := h.data[chatID]; exists {
		return h.data[chatID][h.size-1]
	}
	return ""
}

// Get a copy of a given chat history
func (h history) ChatHistory(chatID int64) []string {
	h.mutex.Lock()
	defer h.mutex.Unlock()
	array, exists := h.data[chatID]
	if exists {
		c := make([]string, h.size, h.size)
		copy(c, array)
		return c
	}
	return nil
}

// Add a message at the end of a chat and move everithyng up
// Assert that the slice exists and mutex already locked
func (h history) append(chatID int64, m string) {
	c := make([]string, h.size-1, h.size-1)
	array, _ := h.data[chatID]
	copy(c, array[1:])
	for i, val := range c {
		array[i] = val
	}
	array[h.size-1] = m
}