# Go Watch
[![Build Status](https://drone.broodjeaap.net/api/badges/broodjeaap/go-watch/status.svg)](https://drone.broodjeaap.net/broodjeaap/go-watch)

A change detection server that can notify through various services written in Go

# Intro

GoWatch works through filters, a filter performs operations on the input it recieves.  
Here is an example of a 'Watch' that calculates the lowest and average price of 4090s on NewEgg and notifies the user if the lowest price changed:  
![NewEgg 4090](docs/images/newegg_4090.png)  

Note that everything, including scheduling/storing/notifying, is a `filter`.  

`Schedule` is a [cron](#cron) filter with a '@every 15m' value, so this will run every 15 minutes.  

`NewEgg Fetch` is a [Get URL](#get-url) filter with a 'https://www.newegg.com/p/pl?N=100007709&d=4090&isdeptsrh=1&PageSize=96' value, it's output will be the HTTP response.  

`Select Price` is a [CSS](#css) filter with the value '.item-container .item-action strong[class!="item-buying-choices-price"]' value, it's output will be the html elements containing the prices.  
An [XPath](#xpath) filter could also have been used.  

`Sanitize` is a [Replace](#replace) filter, using a regular expression ('[^0-9]') it removes anything that's not a number.  

`Avg` is an [Average](#average) filter, it calculates the average value of its inputs.  

`Min` is a [Minimum](#minimum) filter, it calculates the minimum value of its inputs.  

`Store Avg` and `Store Min` are [Store](#store) filters, they store its input values in the database.  

`Diff` is a [Different Than Last](#different-then-last) filter, only passing on the inputs that are different then the last value stored in the database.  

`Notify` is a [Notify](#notify) filter, if there are any inputs to this filter, it will execute a template and send the result to a user defined 'notifier' (Telegram/Discord/Matrix/etc).

# Filters

## Cron

## Get URL

## Get URLs

## CSS

## XPath

## JSON

## Replace

## Match

## Substring

## Contains

## Store

## Notify

## Math

### Sum

### Minimum

### Maximum

### Average

### Count

### Round

## Condition

### Different Than Last

### Lower Than Last

### Lowest

### Lower Than

### Higher Than Last

### Highest

### Higher Than

## Lua

## type script compilation

`tsc static/*.ts --lib es2020,dom --watch --downlevelIteration`

# Dependencies

The following libaries are used in Go-Watch:  
- [Gin](https://github.com/gin-gonic/gin) for HTTP server
    - [multitemplate](https://github.com/gin-contrib/multitemplate) for template inheritance
- [Cascadia](https://pkg.go.dev/github.com/andybalholm/cascadia) for CSS selectors
- [htmlquery](https://pkg.go.dev/github.com/antchfx/htmlquery) for XPath selectors
- [validator](https://pkg.go.dev/github.com/go-playground/validator/v10@v10.11.0) for user user input validation
- [tgbotapi](https://pkg.go.dev/github.com/go-telegram-bot-api/telegram-bot-api/v5@v5.5.1) for Telegram
- [cron](https://pkg.go.dev/github.com/robfig/cron/v3@v3.0.0) for job scheduling
- [viper](https://pkg.go.dev/github.com/spf13/viper@v1.12.0) for config management
- [gjson](https://pkg.go.dev/github.com/tidwall/gjson@v1.14.2) for JSON selectors
- [gopher-lua](https://github.com/yuin/gopher-lua) for Lua scripting
    - [gopher-lua-libs](https://pkg.go.dev/github.com/vadv/gopher-lua-libs@v0.4.0) for expanding the Lua scripting functionality
- [net](https://pkg.go.dev/golang.org/x/net) for http fetching
- [gorm](https://pkg.go.dev/gorm.io/gorm@v1.23.8) for database abstraction
    - [sqlite](https://pkg.go.dev/gorm.io/driver/sqlite@v1.3.6)
    - [postgres](https://github.com/go-gorm/postgres)
    - [mysql](https://github.com/go-gorm/mysql)
    - [sqlserver](https://github.com/go-gorm/sqlserver)
- [bootstrap](https://getbootstrap.com/)