// Copyright (c) 2017, OpenPeeDeeP. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package xdg impelements the XDG standard for application file locations.
package xdg

import (
	"os"
	"path/filepath"
	"strings"
)

var defaulter xdgDefaulter = new(osDefaulter)

type xdgDefaulter interface {
	defaultDataHome() string
	defaultDataDirs() []string
	defaultConfigHome() string
	defaultConfigDirs() []string
	defaultCacheHome() string
}

type osDefaulter struct {
}

//This method is used in the testing suit
// nolint: deadcode
func setDefaulter(def xdgDefaulter) {
	defaulter = def
}

// XDG is information about the currently running application
type XDG struct {
	Vendor      string
	Application string
}

// New returns an instance of XDG that is used to grab files for application use
func New(vendor, application string) *XDG {
	return &XDG{
		Vendor:      vendor,
		Application: application,
	}
}

// DataHome returns the location that should be used for user specific data files for this specific application
func (x *XDG) DataHome() string {
	return filepath.Join(DataHome(), x.Vendor, x.Application)
}

// DataDirs returns a list of locations that should be used for system wide data files for this specific application
func (x *XDG) DataDirs() []string {
	dataDirs := DataDirs()
	for i, dir := range dataDirs {
		dataDirs[i] = filepath.Join(dir, x.Vendor, x.Application)
	}
	return dataDirs
}

// ConfigHome returns the location that should be used for user specific config files for this specific application
func (x *XDG) ConfigHome() string {
	return filepath.Join(ConfigHome(), x.Vendor, x.Application)
}

// ConfigDirs returns a list of locations that should be used for system wide config files for this specific application
func (x *XDG) ConfigDirs() []string {
	configDirs := ConfigDirs()
	for i, dir := range configDirs {
		configDirs[i] = filepath.Join(dir, x.Vendor, x.Application)
	}
	return configDirs
}

// CacheHome returns the location that should be used for application cache files for this specific application
func (x *XDG) CacheHome() string {
	return filepath.Join(CacheHome(), x.Vendor, x.Application)
}

// QueryData looks for the given filename in XDG paths for data files.
// Returns an empty string if one was not found.
func (x *XDG) QueryData(filename string) string {
	dirs := x.DataDirs()
	dirs = append([]string{x.DataHome()}, dirs...)
	return returnExist(filename, dirs)
}

// QueryConfig looks for the given filename in XDG paths for config files.
// Returns an empty string if one was not found.
func (x *XDG) QueryConfig(filename string) string {
	dirs := x.ConfigDirs()
	dirs = append([]string{x.ConfigHome()}, dirs...)
	return returnExist(filename, dirs)
}

// QueryCache looks for the given filename in XDG paths for cache files.
// Returns an empty string if one was not found.
func (x *XDG) QueryCache(filename string) string {
	return returnExist(filename, []string{x.CacheHome()})
}

func returnExist(filename string, dirs []string) string {
	for _, dir := range dirs {
		_, err := os.Stat(filepath.Join(dir, filename))
		if (err != nil && os.IsExist(err)) || err == nil {
			return filepath.Join(dir, filename)
		}
	}
	return ""
}

// DataHome returns the location that should be used for user specific data files
func DataHome() string {
	dataHome := os.Getenv("XDG_DATA_HOME")
	if dataHome == "" {
		dataHome = defaulter.defaultDataHome()
	}
	return dataHome
}

// DataDirs returns a list of locations that should be used for system wide data files
func DataDirs() []string {
	var dataDirs []string
	dataDirsStr := os.Getenv("XDG_DATA_DIRS")
	if dataDirsStr != "" {
		dataDirs = strings.Split(dataDirsStr, string(os.PathListSeparator))
	}
	if len(dataDirs) == 0 {
		dataDirs = defaulter.defaultDataDirs()
	}
	return dataDirs
}

// ConfigHome returns the location that should be used for user specific config files
func ConfigHome() string {
	configHome := os.Getenv("XDG_CONFIG_HOME")
	if configHome == "" {
		configHome = defaulter.defaultConfigHome()
	}
	return configHome
}

// ConfigDirs returns a list of locations that should be used for system wide config files
func ConfigDirs() []string {
	var configDirs []string
	configDirsStr := os.Getenv("XDG_CONFIG_DIRS")
	if configDirsStr != "" {
		configDirs = strings.Split(configDirsStr, string(os.PathListSeparator))
	}
	if len(configDirs) == 0 {
		configDirs = defaulter.defaultConfigDirs()
	}
	return configDirs
}

// CacheHome returns the location that should be used for application cache files
func CacheHome() string {
	cacheHome := os.Getenv("XDG_CACHE_HOME")
	if cacheHome == "" {
		cacheHome = defaulter.defaultCacheHome()
	}
	return cacheHome
}