package cabana

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"path"
	"reflect"
	"strings"

	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/pact"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// CompiledSetting is a singleton settings registration after strict schema
// compilation and writable-field binding.
type CompiledSetting struct {
	PluginID string
	Item     pact.SettingsItem
	Form     *FormSchema
	Writable []WritableField
}

// SettingsResult is the explicit missing/existing singleton response.
type SettingsResult struct {
	Exists bool           `json:"exists"`
	Data   map[string]any `json:"data"`
}

// SettingsService reads and transactionally updates compiled singleton rows.
type SettingsService struct{ DB *gorm.DB }

func compileSetting(pluginID string, item pact.SettingsItem, fsys fs.FS) (*CompiledSetting, error) {
	if item.NewModel == nil {
		return nil, fmt.Errorf("cabana: setting %s has no model factory", item.Code)
	}
	model := item.NewModel()
	rv := reflect.ValueOf(model)
	if model == nil || rv.Kind() != reflect.Pointer || rv.IsNil() || rv.Elem().Kind() != reflect.Struct {
		return nil, fmt.Errorf("cabana: setting %s model must be a non-nil struct pointer", item.Code)
	}
	if _, ok := model.(lagoon.HasFillable); !ok {
		return nil, fmt.Errorf("cabana: setting %s model has no Fillable", item.Code)
	}
	if _, ok := model.(hasRules); !ok {
		return nil, fmt.Errorf("cabana: setting %s model has no Rules", item.Code)
	}
	formPath := strings.Trim(path.Clean(item.Form), "/")
	if formPath == "." || strings.HasPrefix(formPath, "..") {
		return nil, fmt.Errorf("cabana: setting %s form escapes the plugin", item.Code)
	}
	raw, err := readAsset(fsys, formPath)
	if err != nil {
		return nil, fmt.Errorf("cabana: plugin %s setting %s schema %s: %w", pluginID, item.Code, formPath, err)
	}
	fields, err := decodeFields(raw)
	if err != nil {
		return nil, fmt.Errorf("cabana: plugin %s setting %s schema %s: %w", pluginID, item.Code, formPath, err)
	}
	form := &FormSchema{Name: item.Label, ModelClass: item.Model, Fields: fields}
	columns := modelColumns(model)
	fillable := map[string]struct{}{}
	for _, key := range model.(lagoon.HasFillable).Fillable() {
		fillable[key] = struct{}{}
	}
	writable := make([]WritableField, 0, len(fields))
	for _, field := range fields {
		if !scalarFormField(field.Type) || protectedFillKey(field.Name) {
			continue
		}
		if _, ok := columns[field.Name]; !ok {
			return nil, fmt.Errorf("cabana: setting %s field %s is not a model column", item.Code, field.Name)
		}
		if _, ok := fillable[field.Name]; !ok {
			return nil, fmt.Errorf("cabana: setting %s field %s is not fillable", item.Code, field.Name)
		}
		writable = append(writable, WritableField{Name: field.Name, FillKey: field.Name})
	}
	return &CompiledSetting{PluginID: pluginID, Item: item, Form: form, Writable: writable}, nil
}

// Get returns default-valued data without creating a missing singleton.
func (s SettingsService) Get(ctx context.Context, setting *CompiledSetting) (SettingsResult, error) {
	if s.DB == nil {
		return SettingsResult{}, errors.New("cabana: database is not configured")
	}
	model, err := newSettingModel(setting)
	if err != nil {
		return SettingsResult{}, err
	}
	if err := applySettingDefaults(setting, model); err != nil {
		return SettingsResult{}, err
	}
	err = s.DB.WithContext(ctx).Where(clause.Eq{Column: clause.Column{Name: primaryColumn(model)}, Value: 1}).Take(model).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return SettingsResult{Exists: false, Data: projectSetting(setting, model)}, nil
	}
	if err != nil {
		return SettingsResult{}, err
	}
	return SettingsResult{Exists: true, Data: projectSetting(setting, model)}, nil
}

// Put validates and persists exactly one settings row. Identical replay is a
// successful no-op, including no updated_at churn.
func (s SettingsService) Put(ctx context.Context, setting *CompiledSetting, body map[string]any) (SettingsResult, error) {
	if s.DB == nil {
		return SettingsResult{}, errors.New("cabana: database is not configured")
	}
	if err := requireSettingInputs(setting, body); err != nil {
		return SettingsResult{}, err
	}
	var result SettingsResult
	err := s.DB.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		model, err := newSettingModel(setting)
		if err != nil {
			return err
		}
		pk := primaryColumn(model)
		err = tx.Clauses(clause.Locking{Strength: "UPDATE"}).Where(clause.Eq{Column: clause.Column{Name: pk}, Value: 1}).Take(model).Error
		exists := err == nil
		if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
			return err
		}
		if !exists {
			if err := applySettingDefaults(setting, model); err != nil {
				return err
			}
			if err := setColumn(model, pk, uint(1)); err != nil {
				return err
			}
		}
		before := projectSetting(setting, model)
		projected := projectSettingBody(setting, body)
		allowed := make([]string, 0, len(setting.Writable))
		for _, field := range setting.Writable {
			allowed = append(allowed, field.FillKey)
		}
		if err := lagoon.Fill(model, allowed, projected, false); err != nil {
			return &ValidationError{Details: map[string]any{"body": []string{"The settings payload is invalid."}}}
		}
		if hook, ok := model.(lagoon.HasBeforeValidate); ok && hook != nil {
			if err := hook.BeforeValidate(tx); err != nil {
				return err
			}
		}
		rules := settingRules(setting, model)
		messages, err := lagoon.Validate(ctx, tx, model, rules, valuesForRules(model, rules), nil)
		if err != nil {
			return err
		}
		if len(messages) > 0 {
			return &ValidationError{Details: validationDetails(messages)}
		}
		after := projectSetting(setting, model)
		if !exists {
			if err := tx.Create(model).Error; err != nil {
				return err
			}
		} else if !reflect.DeepEqual(before, after) {
			if err := tx.Save(model).Error; err != nil {
				return err
			}
		}
		result = SettingsResult{Exists: true, Data: after}
		return nil
	})
	return result, err
}

func newSettingModel(setting *CompiledSetting) (any, error) {
	if setting == nil || setting.Item.NewModel == nil {
		return nil, errors.New("cabana: setting model is not configured")
	}
	model := setting.Item.NewModel()
	rv := reflect.ValueOf(model)
	if model == nil || rv.Kind() != reflect.Pointer || rv.IsNil() || rv.Elem().Kind() != reflect.Struct {
		return nil, errors.New("cabana: setting model is invalid")
	}
	return model, nil
}

func applySettingDefaults(setting *CompiledSetting, model any) error {
	defaults := map[string]any{}
	for _, field := range setting.Form.Fields {
		if field.Default == nil {
			continue
		}
		var value any
		if err := json.Unmarshal(field.Default.raw, &value); err != nil {
			return err
		}
		if field.Type == "switch" || field.Type == "checkbox" {
			switch typed := value.(type) {
			case float64:
				value = typed != 0
			case json.Number:
				value = typed.String() != "0"
			}
		}
		defaults[field.Name] = value
	}
	return lagoon.Fill(model, settingWritable(setting), defaults, true)
}

func settingWritable(setting *CompiledSetting) []string {
	out := make([]string, 0, len(setting.Writable))
	for _, field := range setting.Writable {
		out = append(out, field.FillKey)
	}
	return out
}

func projectSettingBody(setting *CompiledSetting, body map[string]any) map[string]any {
	out := map[string]any{}
	if setting == nil {
		return out
	}
	for _, field := range setting.Writable {
		value, ok := body[field.Name]
		if ok && !nestedValue(value) {
			out[field.FillKey] = value
		}
	}
	return out
}

func projectSetting(setting *CompiledSetting, model any) map[string]any {
	out := map[string]any{}
	value := reflect.ValueOf(model)
	for value.IsValid() && value.Kind() == reflect.Pointer {
		if value.IsNil() {
			return out
		}
		value = value.Elem()
	}
	if !value.IsValid() || value.Kind() != reflect.Struct || setting == nil {
		return out
	}
	for _, field := range setting.Writable {
		v := fieldByColumn(value, field.FillKey)
		if v.IsValid() && v.CanInterface() {
			out[field.Name] = v.Interface()
		}
	}
	return out
}

func requireSettingInputs(setting *CompiledSetting, body map[string]any) error {
	details := map[string]any{}
	for _, field := range setting.Form.Fields {
		value, present := body[field.Name]
		if present && nestedValue(value) {
			details[field.Name] = []string{"The " + field.Name + " field is invalid."}
			continue
		}
		if field.Required && !present {
			details[field.Name] = []string{"The " + field.Name + " field is required."}
		}
	}
	if len(details) > 0 {
		return &ValidationError{Details: details}
	}
	return nil
}

func settingRules(setting *CompiledSetting, model any) map[string]string {
	rules := map[string]string{}
	if provider, ok := model.(hasRules); ok && provider != nil {
		for key, rule := range provider.Rules() {
			rules[key] = rule
		}
	}
	for _, field := range setting.Form.Fields {
		if field.Required {
			rules[field.Name] = mergeRequired(rules[field.Name])
		}
	}
	return rules
}

func setColumn(model any, column string, value any) error {
	rv := reflect.ValueOf(model)
	for rv.Kind() == reflect.Pointer {
		if rv.IsNil() {
			return errors.New("cabana: nil model")
		}
		rv = rv.Elem()
	}
	field := fieldByColumn(rv, column)
	if !field.IsValid() || !field.CanSet() {
		return fmt.Errorf("cabana: model has no writable %s column", column)
	}
	src := reflect.ValueOf(value)
	if src.Type().AssignableTo(field.Type()) {
		field.Set(src)
		return nil
	}
	if src.Type().ConvertibleTo(field.Type()) {
		field.Set(src.Convert(field.Type()))
		return nil
	}
	return fmt.Errorf("cabana: cannot set %s", column)
}