package updaters

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"slices"
	"strings"
	"time"

	"github.com/qdm12/dns/v2/pkg/doh"
	dnsprovider "github.com/qdm12/dns/v2/pkg/provider"
	"github.com/qdm12/gluetun-servers/pkg/models"
	publicipapi "github.com/qdm12/gluetun-servers/pkg/publicip/api"
	"github.com/qdm12/gluetun-servers/pkg/updaters/common"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/airvpn"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/cyberghost"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/expressvpn"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/fastestvpn"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/giganews"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/hidemyass"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/ipvanish"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/ivpn"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/mullvad"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/nordvpn"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/perfectprivacy"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/privado"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/privateinternetaccess"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/privatevpn"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/protonvpn"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/purevpn"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/slickvpn"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/surfshark"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/torguard"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/vpnsecure"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/vpnunlimited"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/vyprvpn"
	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/windscribe"
	"github.com/qdm12/gluetun-servers/pkg/updaters/resolver"
	"github.com/qdm12/gluetun-servers/pkg/updaters/unzip"
	"github.com/qdm12/gosettings"
)

// UpdateAllSettings contains the configuration for the [UpdateAll] function.
type UpdateAllSettings struct {
	// OutputPath is the directory where the provider JSON files will be written.
	// It defaults to the current directory if left unset.
	OutputPath *string
	// ProtonEmail is the email for the ProtonVPN account, which is required
	// to update ProtonVPN servers.
	ProtonEmail *string
	// ProtonPassword is the password for the ProtonVPN account, which is required
	// to update ProtonVPN servers.
	ProtonPassword *string
	// IpinfoToken is the API token for the IPInfo public IP API.
	// If not provided, the IP fetcher will still work but may be
	// subject to stricter rate limits for ipinfo.io.
	IpinfoToken *string
	// MinServers is a map of provider name to minimum number of servers required for a successful update.
	// If a provider has fewer servers than the specified minimum, the update will be considered a failure
	// for that provider. If the provider name is not found in this map, it is assumed that there is no
	// minimum server requirement for that provider.
	MinServers map[string]uint
}

func (s *UpdateAllSettings) setDefaults() {
	s.OutputPath = gosettings.DefaultPointer(s.OutputPath, "")
	s.ProtonEmail = gosettings.DefaultPointer(s.ProtonEmail, "")
	s.ProtonPassword = gosettings.DefaultPointer(s.ProtonPassword, "")
	s.IpinfoToken = gosettings.DefaultPointer(s.IpinfoToken, "")
	if s.MinServers == nil {
		s.MinServers = make(map[string]uint)
	}
}

var (
	errProtonEmailRequired        = errors.New("proton email is required for updating ProtonVPN servers")
	errProtonPasswordRequired     = errors.New("proton password is required for updating ProtonVPN servers")
	errMinServersProviderNotFound = errors.New("provider name in MinServers not found in list of all providers")
)

func (s *UpdateAllSettings) validate() error {
	switch {
	case *s.ProtonEmail == "":
		return fmt.Errorf("%w", errProtonEmailRequired)
	case *s.ProtonPassword == "":
		return fmt.Errorf("%w", errProtonPasswordRequired)
	}

	allProviders := ListAllNames()
	for providerName := range s.MinServers {
		if !slices.Contains(allProviders, providerName) {
			return fmt.Errorf("%w: %s", errMinServersProviderNotFound, providerName)
		}
	}

	return nil
}

// ListAllNames returns a list of all provider names supported by [UpdateAll].
// It is exported notably to validate from the gluetun repository if it matches
// the list of providers in the internal/constants/providers package.
func ListAllNames() []string {
	fetchers := [...]interface {
		Name() string
	}{
		&airvpn.Updater{},
		&cyberghost.Updater{},
		&expressvpn.Updater{},
		&fastestvpn.Updater{},
		&giganews.Updater{},
		&hidemyass.Updater{},
		&ipvanish.Updater{},
		&ivpn.Updater{},
		&mullvad.Updater{},
		&nordvpn.Updater{},
		&perfectprivacy.Updater{},
		&privado.Updater{},
		&privateinternetaccess.Updater{},
		&privatevpn.Updater{},
		&protonvpn.Updater{},
		&purevpn.Updater{},
		&slickvpn.Updater{},
		&surfshark.Updater{},
		&torguard.Updater{},
		&vpnsecure.Updater{},
		&vpnunlimited.Updater{},
		&vyprvpn.Updater{},
		&windscribe.Updater{},
	}
	names := make([]string, len(fetchers))
	for i, fetcher := range fetchers {
		names[i] = fetcher.Name()
	}
	return names
}

type Logger interface {
	Warn(message string)
}

var errUpdateAllFailed = errors.New("update failed for one or more providers")

// UpdateAll fetches server data for all providers in parallel and writes each
// provider's data as <provider-name>.json into the output path specified.
// Errors for individual providers are collected and returned as a combined error.
func UpdateAll(ctx context.Context, client *http.Client, logger Logger, settings UpdateAllSettings) error {
	settings.setDefaults()
	err := settings.validate()
	if err != nil {
		return fmt.Errorf("validating settings: %w", err)
	}

	const permission = 0o755
	err = os.MkdirAll(*settings.OutputPath, permission)
	if err != nil {
		return fmt.Errorf("creating output directory: %w", err)
	}

	dohDialer, err := doh.New(doh.Settings{
		UpstreamResolvers: []dnsprovider.Provider{
			dnsprovider.Cloudflare(),
			dnsprovider.Google(),
		},
	})
	if err != nil {
		return fmt.Errorf("creating updater DoH dialer: %w", err)
	}
	parallelResolver := resolver.NewParallelResolver(dohDialer)
	unzipper := unzip.New(client)
	ipFetcher, err := buildIPFetcher(client, logger, *settings.IpinfoToken)
	if err != nil {
		return fmt.Errorf("creating IP fetcher: %w", err)
	}
	fetchers := buildFetchers(client, parallelResolver, unzipper, ipFetcher,
		logger, *settings.ProtonEmail, *settings.ProtonPassword)

	results := make(chan error)

	allProviders := ListAllNames()
	for _, providerName := range allProviders {
		go func(providerName string) {
			fetcher := fetchers[providerName]
			minServers := settings.MinServers[providerName]
			err := fetchAndWrite(ctx, providerName, fetcher, minServers, *settings.OutputPath)
			if err != nil {
				err = fmt.Errorf("provider %s: %w", providerName, err)
			}
			results <- err
		}(providerName)
	}

	errs := make([]string, 0, len(allProviders))
	for range allProviders {
		err := <-results
		if err != nil {
			errs = append(errs, err.Error())
		}
	}

	if len(errs) > 0 {
		return fmt.Errorf("%w:\n%s", errUpdateAllFailed, strings.Join(errs, "\n"))
	}
	return nil
}

func buildIPFetcher(client *http.Client, logger Logger, ipinfoToken string) (
	fetcher *publicipapi.ResilientFetcher, err error,
) {
	nameTokenPairs := []publicipapi.NameToken{
		{Name: string(publicipapi.IPInfo), Token: ipinfoToken},
		{Name: string(publicipapi.IP2Location)},
		{Name: string(publicipapi.IfConfigCo)},
	}
	fetchers, err := publicipapi.New(nameTokenPairs, client)
	if err != nil {
		return nil, fmt.Errorf("creating public IP fetchers: %w", err)
	}
	fetcher = publicipapi.NewResilient(fetchers, logger)
	return fetcher, nil
}

func buildFetchers(client *http.Client, parallelResolver common.ParallelResolver,
	unzipper common.Unzipper, ipFetcher common.IPFetcher,
	logger Logger, protonEmail, protonPassword string,
) map[string]common.Fetcher {
	fetchers := [...]common.Fetcher{
		airvpn.New(client),
		cyberghost.New(parallelResolver, logger),
		expressvpn.New(unzipper, logger, parallelResolver),
		fastestvpn.New(client, logger, parallelResolver),
		giganews.New(unzipper, logger, parallelResolver),
		hidemyass.New(client, logger, parallelResolver),
		ipvanish.New(unzipper, logger, parallelResolver),
		ivpn.New(client, logger, parallelResolver),
		mullvad.New(client),
		nordvpn.New(client, logger),
		perfectprivacy.New(unzipper, logger),
		privado.New(client, logger),
		privateinternetaccess.New(client),
		privatevpn.New(unzipper, logger, parallelResolver),
		protonvpn.New(client, logger, protonEmail, protonPassword),
		purevpn.New(ipFetcher, unzipper, logger, parallelResolver),
		slickvpn.New(client, logger, parallelResolver),
		surfshark.New(client, unzipper, logger, parallelResolver),
		torguard.New(unzipper, logger, parallelResolver),
		vpnsecure.New(client, logger, parallelResolver),
		vpnunlimited.New(unzipper, logger, parallelResolver),
		vyprvpn.New(unzipper, logger, parallelResolver),
		windscribe.New(client, logger),
	}
	nameToFetcher := make(map[string]common.Fetcher, len(fetchers))
	for _, fetcher := range fetchers {
		nameToFetcher[fetcher.Name()] = fetcher
	}
	return nameToFetcher
}

func fetchAndWrite(ctx context.Context, providerName string, fetcher common.Fetcher,
	minServers uint, outputDirPath string,
) error {
	filename := strings.ToLower(strings.ReplaceAll(providerName, " ", "")) + ".json"
	destinationPath := filepath.Join(outputDirPath, filename)
	const permission = 0o644
	file, err := os.OpenFile(destinationPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, permission)
	if err != nil {
		return fmt.Errorf("opening output file: %w", err)
	}

	servers, err := fetcher.FetchServers(ctx, int(minServers)) //nolint:gosec
	if err != nil {
		_ = file.Close()
		_ = os.Remove(destinationPath)
		return fmt.Errorf("fetching servers: %w", err)
	}
	data := models.Servers{
		Version:   fetcher.Version(),
		Timestamp: time.Now().Unix(),
		Servers:   servers,
	}

	encoder := json.NewEncoder(file)
	encoder.SetIndent("", "  ")
	err = encoder.Encode(data)
	if err != nil {
		_ = file.Close()
		return fmt.Errorf("encoding servers to JSON: %w", err)
	}

	err = file.Close()
	if err != nil {
		return fmt.Errorf("closing output file: %w", err)
	}

	return nil
}