algernon/engine/cache.go

package engine

import (
	"net/http"

	"github.com/xyproto/datablock"
	lua "github.com/xyproto/gopher-lua"
)

// DataToClient is a helper function for sending file data (that might be cached) to a HTTP client
func (ac *Config) DataToClient(w http.ResponseWriter, req *http.Request, filename string, data []byte) {
	datablock.NewDataBlock(data, true).ToClient(w, req, filename, ac.ClientCanGzip(req), gzipThreshold)
}

// DataToClientModernBrowsers is a helper function for sending file data (that might be cached) to a HTTP client
func DataToClientModernBrowsers(w http.ResponseWriter, req *http.Request, filename string, data []byte) {
	datablock.NewDataBlock(data, true).ToClient(w, req, filename, true, gzipThreshold)
}

// LoadCacheFunctions loads functions related to caching into the given Lua state
func (ac *Config) LoadCacheFunctions(L *lua.LState) {
	const disabledMessage = "Caching is disabled"
	const clearedMessage = "Cache cleared"

	luaCacheStatsFunc := L.NewFunction(func(L *lua.LState) int {
		if ac.cache == nil {
			L.Push(lua.LString(disabledMessage))
			return 1 // number of results
		}
		info := ac.cache.Stats()
		// Return the string, but drop the final newline
		L.Push(lua.LString(info[:len(info)-1]))
		return 1 // number of results
	})

	// Return information about the cache use
	L.SetGlobal("CacheInfo", luaCacheStatsFunc)
	L.SetGlobal("CacheStats", luaCacheStatsFunc) // undocumented alias

	// Clear the cache
	L.SetGlobal("ClearCache", L.NewFunction(func(L *lua.LState) int {
		if ac.cache == nil {
			L.Push(lua.LString(disabledMessage))
			return 1 // number of results
		}
		ac.cache.Clear()
		L.Push(lua.LString(clearedMessage))
		return 1 // number of results
	}))

	// Try to load a file into the file cache, if it isn't already there
	L.SetGlobal("preload", L.NewFunction(func(L *lua.LState) int {
		filename := L.ToString(1)
		if ac.cache == nil {
			L.Push(lua.LBool(false))
			return 1 // number of results
		}
		// Don't read from disk if already in cache, hence "true"
		if _, err := ac.cache.Read(filename, true); err != nil {
			L.Push(lua.LBool(false))
			return 1 // number of results
		}
		L.Push(lua.LBool(true)) // success
		return 1                // number of results
	}))
}