package service

import (
	"context"
	"fmt"
	"strings"
	"sync"
	"time"

	"github.com/cortezaproject/corteza/server/pkg/actionlog"
	"github.com/spf13/cast"

	"github.com/cortezaproject/corteza/server/pkg/errors"
	"github.com/cortezaproject/corteza/server/pkg/logger"
	"github.com/cortezaproject/corteza/server/pkg/options"
	"github.com/cortezaproject/corteza/server/store"
	"github.com/cortezaproject/corteza/server/system/types"
	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"
)

type (
	settings struct {
		actionlog     actionlog.Recorder
		store         store.SettingValues
		accessControl accessController
		logger        *zap.Logger
		m             sync.RWMutex
		webappsConf   options.WebappOpt

		// Holds reference to the "current" settings that
		// are used by the services
		current interface{}

		// update channel we'll write set of changed settings when change occurs
		update chan types.SettingValueSet

		listeners []registeredSettingsListener
	}

	accessController interface {
		CanReadSettings(ctx context.Context) bool
		CanManageSettings(ctx context.Context) bool
	}

	SettingsChangeListener     func(ctx context.Context, current interface{}, set types.SettingValueSet)
	registeredSettingsListener struct {
		prefix string
		fn     SettingsChangeListener
	}
)

func Settings(ctx context.Context, s store.SettingValues, log *zap.Logger, ac accessController, al actionlog.Recorder, current interface{}, webappsConf options.WebappOpt) *settings {
	svc := &settings{
		actionlog:     al,
		store:         s,
		accessControl: ac,
		logger:        log.Named("settings"),
		current:       current,
		webappsConf:   webappsConf,
		listeners:     make([]registeredSettingsListener, 0, 2),
		update:        make(chan types.SettingValueSet, 0),
	}

	svc.watch(ctx)

	return svc
}

func (svc *settings) Register(prefix string, listener SettingsChangeListener) {
	svc.logger.Debug("registering new settings change listener", zap.String("prefix", prefix))

	svc.m.Lock()
	defer svc.m.Unlock()

	svc.listeners = append(svc.listeners, registeredSettingsListener{
		prefix: prefix,
		fn:     listener,
	})
}

func (svc *settings) watch(ctx context.Context) {
	go func() {
		for {
			select {
			case vv := <-svc.update:
				svc.notify(ctx, vv)
			case <-ctx.Done():
				return
			}
		}
	}()
}

func (svc *settings) notify(ctx context.Context, vv types.SettingValueSet) {
	svc.m.RLock()
	defer svc.m.RUnlock()

	for _, l := range svc.listeners {
		go func(l registeredSettingsListener, vv types.SettingValueSet) {
			if len(l.prefix) > 0 {
				vv = vv.FilterByPrefix(l.prefix)
			}

			svc.logger.Debug(
				"notifying listener",
				zap.String("prefix", l.prefix),
				zap.Int("changes", len(vv)),
			)

			if len(vv) > 0 {
				l.fn(ctx, svc.current, vv)
			}
		}(l, vv)
	}
}

func (svc *settings) log(ctx context.Context, fields ...zapcore.Field) *zap.Logger {
	return logger.AddRequestID(ctx, svc.logger).With(fields...)
}

func (svc *settings) FindByPrefix(ctx context.Context, pp ...string) (types.SettingValueSet, error) {
	if !svc.accessControl.CanReadSettings(ctx) {
		return nil, SettingsErrNotAllowedToRead()
	}

	return svc.findByPrefix(ctx, pp...)
}

func (svc *settings) findByPrefix(ctx context.Context, pp ...string) (types.SettingValueSet, error) {
	var (
		f = types.SettingsFilter{
			Prefix: strings.Join(pp, "."),
			Check:  func(*types.SettingValue) (bool, error) { return true, nil },
		}
	)

	vv, _, err := store.SearchSettingValues(ctx, svc.store, f)
	return vv, err
}

func (svc *settings) Get(ctx context.Context, name string, ownedBy uint64) (out *types.SettingValue, err error) {
	if !svc.accessControl.CanReadSettings(ctx) {
		return nil, SettingsErrNotAllowedToRead()
	}

	out, err = store.LookupSettingValueByNameOwnedBy(ctx, svc.store, name, ownedBy)
	if err != nil && !errors.IsNotFound(err) {
		return nil, err
	}

	return out, nil
}

func (svc *settings) UpdateCurrent(ctx context.Context) error {
	if vv, err := svc.findByPrefix(ctx); err != nil {
		return err
	} else {
		return svc.updateCurrent(ctx, vv)
	}
}

func (svc *settings) updateCurrent(ctx context.Context, vv types.SettingValueSet) (err error) {
	// update current settings with new values
	if err = vv.KV().Decode(svc.current); err != nil {
		return fmt.Errorf("could not decode settings into KV: %w", err)
	}

	// push message over update chan so that we can notify all settings listeners
	select {
	case svc.update <- vv:
	case <-ctx.Done():
		return ctx.Err()
	case <-time.After(time.Second):
		svc.logger.Warn("timed-out while waiting to update current settings")
	}

	return nil
}

func (svc *settings) Set(ctx context.Context, v *types.SettingValue) (err error) {
	if !svc.accessControl.CanManageSettings(ctx) {
		return SettingsErrNotAllowedToManage()
	}

	if _, err = check(v); err != nil {
		return
	}

	var current *types.SettingValue
	current, err = store.LookupSettingValueByNameOwnedBy(ctx, svc.store, v.Name, v.OwnedBy)
	if errors.IsNotFound(err) {
		v.UpdatedAt = *now()
		err = store.CreateSettingValue(ctx, svc.store, v)
	} else if err != nil {
		return err
	}

	if !current.Eq(v) {
		v.UpdatedAt = *now()
		err = store.UpdateSettingValue(ctx, svc.store, v)
	}

	if err != nil || current.Eq(v) {
		// Return on error or when there is nothing to update (same value)
		return
	}

	svc.logChange(ctx, v)
	return svc.updateCurrent(ctx, types.SettingValueSet{v})
}

func (svc *settings) BulkSet(ctx context.Context, vv types.SettingValueSet) (err error) {
	if !svc.accessControl.CanManageSettings(ctx) {
		return SettingsErrNotAllowedToManage()
	}

	if _, err = check(vv...); err != nil {
		return
	}

	// Load current settings and get changed values
	var current, old, new types.SettingValueSet
	if current, err = svc.FindByPrefix(ctx); err != nil {
		return
	} else {
		vv = current.Changed(vv)
		_ = vv.Walk(func(v *types.SettingValue) error {
			v.UpdatedAt = *now()
			return nil
		})

		old = current.Old(vv)
		new = current.New(vv)
	}

	if err = store.UpdateSettingValue(ctx, svc.store, old...); err != nil {
		return
	}

	if err = store.CreateSettingValue(ctx, svc.store, new...); err != nil {
		return
	}

	if err = store.DeleteSettingValue(ctx, svc.store, vv.Trash()...); err != nil {
		return
	}

	for _, v := range vv {
		// if any of webapps stylesheet settings is updated, we need to recompute and update affected theme css
		if v.Name == "ui.studio.themes" || v.Name == "ui.studio.custom-css" {
			var compStyles *types.SettingValue
			if v.Name == "ui.studio.themes" {
				compStyles = current.FindByName("ui.studio.custom-css")
			} else {
				compStyles = current.FindByName("ui.studio.themes")
			}

            DefaultStylesheet.updateCSS(v, current.FindByName(v.Name), compStyles, v.Name, svc.webappsConf.ScssDirPath, svc.logger)
		}

		svc.logChange(ctx, v)
	}

	return svc.updateCurrent(ctx, vv)
}

func (svc *settings) logChange(ctx context.Context, v *types.SettingValue) {
	svc.log(ctx,
		zap.String("name", v.Name),
		logger.Uint64("owned-by", v.OwnedBy),
		zap.Stringer("value", v.Value)).
		WithOptions(zap.AddCallerSkip(1)).
		Debug("setting value updated")
}

func (svc *settings) Delete(ctx context.Context, name string, ownedBy uint64) error {
	if !svc.accessControl.CanManageSettings(ctx) {
		return SettingsErrNotAllowedToManage()
	}

	current, err := store.LookupSettingValueByNameOwnedBy(ctx, svc.store, name, ownedBy)
	if errors.IsNotFound(err) {
		return nil
	} else if err != nil {
		return err
	}

	err = store.DeleteSettingValue(ctx, svc.store, current)
	if err != nil {
		return err
	}

	vv := types.SettingValueSet{current}

	svc.log(ctx,
		zap.String("name", name),
		logger.Uint64("owned-by", ownedBy)).Info("setting value removed")

	return svc.updateCurrent(ctx, vv)
}

// Check validates settings values
func check(vv ...*types.SettingValue) (ok bool, err error) {
	set := append(types.SettingValueSet{}, vv...)
	err = set.Walk(func(val *types.SettingValue) error {
		if val == nil || val.Value == nil {
			return err
		}

		vs := val.String()
		if len(vs) == 0 && len(val.Value.String()) > 0 {
			vs = val.Value.String()
		}

		// Password constraints: The min password length should be 8
		if val.Name == "auth.internal.password-constraints.min-length" {
			if cast.ToInt(vs) < passwordMinLength {
				return SettingsErrInvalidPasswordMinLength()
			}
		}

		// Password constraints: The min upper case count should not be a negative number
		if val.Name == "auth.internal.password-constraints.min-upper-case" {
			if cast.ToInt(vs) < 0 {
				return SettingsErrInvalidPasswordMinUpperCase()
			}
		}

		// Password constraints: The min lower case count should not be a negative number
		if val.Name == "auth.internal.password-constraints.min-lower-case" {
			if cast.ToInt(vs) < 0 {
				return SettingsErrInvalidPasswordMinLowerCase()
			}
		}

		// Password constraints: The min number of numeric characters should not be a negative number
		if val.Name == "auth.internal.password-constraints.min-num-count" {
			if cast.ToInt(vs) < 0 {
				return SettingsErrInvalidPasswordMinNumCount()
			}
		}

		// Password constraints: The min number of special characters should not be a negative number
		if val.Name == "auth.internal.password-constraints.min-special-count" {
			if cast.ToInt(vs) < 0 {
				return SettingsErrInvalidPasswordMinSpecialCharCount()
			}
		}

		return err
	})
	if err != nil {
		return false, err
	}

	return true, nil
}