package redirection

import (
	"encoding/json"
	"log"
	"os"
	"path"
	"path/filepath"
	"regexp"
	"strings"
	"sync"

	"imuslab.com/zoraxy/mod/info/logger"
	"imuslab.com/zoraxy/mod/utils"
)

type RuleTable struct {
	AllowRegex bool //Allow regular expression to be used in rule matching. Require up to O(n^m) time complexity
	Logger     *logger.Logger
	configPath string   //The location where the redirection rules is stored
	rules      sync.Map //Store the redirection rules for this reverse proxy instance

}

type RedirectRules struct {
	RedirectURL      string //The matching URL to redirect
	TargetURL        string //The destination redirection url
	ForwardChildpath bool   //Also redirect the pathname
	StatusCode       int    //Status Code for redirection
}

func NewRuleTable(configPath string, allowRegex bool, logger *logger.Logger) (*RuleTable, error) {
	thisRuleTable := RuleTable{
		rules:      sync.Map{},
		configPath: configPath,
		AllowRegex: allowRegex,
		Logger:     logger,
	}
	//Load all the rules from the config path
	if !utils.FileExists(configPath) {
		os.MkdirAll(configPath, 0775)
	}

	// Load all the *.json from the configPath
	files, err := filepath.Glob(filepath.Join(configPath, "*.json"))
	if err != nil {
		return nil, err
	}

	// Parse the json content into RedirectRules
	var rules []*RedirectRules
	for _, file := range files {
		b, err := os.ReadFile(file)
		if err != nil {
			continue
		}

		thisRule := RedirectRules{}

		err = json.Unmarshal(b, &thisRule)
		if err != nil {
			continue
		}

		rules = append(rules, &thisRule)
	}

	//Map the rules into the sync map
	for _, rule := range rules {
		thisRuleTable.log("Redirection rule added: "+rule.RedirectURL+" -> "+rule.TargetURL, nil)
		thisRuleTable.rules.Store(rule.RedirectURL, rule)
	}

	return &thisRuleTable, nil
}

func (t *RuleTable) AddRedirectRule(redirectURL string, destURL string, forwardPathname bool, statusCode int) error {
	// Create a new RedirectRules object with the given parameters
	newRule := &RedirectRules{
		RedirectURL:      redirectURL,
		TargetURL:        destURL,
		ForwardChildpath: forwardPathname,
		StatusCode:       statusCode,
	}

	// Convert the redirectURL to a valid filename by replacing "/" with "-" and "." with "_"
	filename := utils.ReplaceSpecialCharacters(redirectURL) + ".json"

	// Create the full file path by joining the t.configPath with the filename
	filepath := path.Join(t.configPath, filename)

	// Create a new file for writing the JSON data
	file, err := os.Create(filepath)
	if err != nil {
		t.log("Error creating file "+filepath, err)
		return err
	}
	defer file.Close()

	// Encode the RedirectRules object to JSON and write it to the file
	err = json.NewEncoder(file).Encode(newRule)
	if err != nil {
		t.log("Error encoding JSON to file "+filepath, err)
		return err
	}

	// Store the RedirectRules object in the sync.Map
	t.rules.Store(redirectURL, newRule)

	return nil
}

// Edit an existing redirection rule, the oldRedirectURL is used to find the rule to be edited
func (t *RuleTable) EditRedirectRule(oldRedirectURL string, newRedirectURL string, destURL string, forwardPathname bool, statusCode int) error {
	newRule := &RedirectRules{
		RedirectURL:      newRedirectURL,
		TargetURL:        destURL,
		ForwardChildpath: forwardPathname,
		StatusCode:       statusCode,
	}

	//Remove the old rule
	t.DeleteRedirectRule(oldRedirectURL)

	// Convert the redirectURL to a valid filename by replacing "/" with "-" and "." with "_"
	filename := utils.ReplaceSpecialCharacters(newRedirectURL) + ".json"
	filepath := path.Join(t.configPath, filename)

	// Create a new file for writing the JSON data
	file, err := os.Create(filepath)
	if err != nil {
		t.log("Error creating file "+filepath, err)
		return err
	}
	defer file.Close()

	err = json.NewEncoder(file).Encode(newRule)
	if err != nil {
		t.log("Error encoding JSON to file "+filepath, err)
		return err
	}

	// Update the runtime map
	t.rules.Store(newRedirectURL, newRule)

	return nil
}

func (t *RuleTable) DeleteRedirectRule(redirectURL string) error {
	// Convert the redirectURL to a valid filename by replacing "/" with "-" and "." with "_"
	filename := utils.ReplaceSpecialCharacters(redirectURL) + ".json"

	// Create the full file path by joining the t.configPath with the filename
	filepath := path.Join(t.configPath, filename)

	// Check if the file exists
	if _, err := os.Stat(filepath); os.IsNotExist(err) {
		return nil // File doesn't exist, nothing to delete
	}

	// Delete the file
	if err := os.Remove(filepath); err != nil {
		t.log("Error deleting file "+filepath, err)
		return err
	}

	// Delete the key-value pair from the sync.Map
	t.rules.Delete(redirectURL)

	return nil
}

// Get a list of all the redirection rules
func (t *RuleTable) GetAllRedirectRules() []*RedirectRules {
	rules := []*RedirectRules{}
	t.rules.Range(func(key, value interface{}) bool {
		r, ok := value.(*RedirectRules)
		if ok {
			rules = append(rules, r)
		}
		return true
	})
	return rules
}

// Check if a given request URL matched any of the redirection rule
func (t *RuleTable) MatchRedirectRule(requestedURL string) *RedirectRules {
	// Iterate through all the keys in the rules map
	var targetRedirectionRule *RedirectRules = nil
	var maxMatch int = 0
	t.rules.Range(func(key interface{}, value interface{}) bool {
		// Check if the requested URL starts with the key as a prefix
		if t.AllowRegex {
			//Regexp matching rule
			matched, err := regexp.MatchString(key.(string), requestedURL)
			if err != nil {
				//Something wrong with the regex?
				t.log("Unable to match regex", err)
				return true
			}
			if matched {
				maxMatch = len(key.(string))
				targetRedirectionRule = value.(*RedirectRules)
			}

		} else {
			//Default: prefix matching redirect
			if strings.HasPrefix(requestedURL, key.(string)) {
				// This request URL matched the domain
				if len(key.(string)) > maxMatch {
					maxMatch = len(key.(string))
					targetRedirectionRule = value.(*RedirectRules)
				}
			}
		}

		return true
	})

	return targetRedirectionRule
}

// Log the message to log file, use STDOUT if logger not set
func (t *RuleTable) log(message string, err error) {
	if t.Logger == nil {
		if err == nil {
			log.Println("[Redirect] " + message)
		} else {
			log.Println("[Redirect] " + message + ": " + err.Error())
		}
	} else {
		t.Logger.PrintAndLog("redirect", message, err)
	}
}