// Copyright (c) Abstract Machines
// SPDX-License-Identifier: Apache-2.0

package journal

import (
	"context"
	"encoding/json"
	"time"

	apiutil "github.com/absmach/magistrala/api/http/util"
	smqauthn "github.com/absmach/magistrala/pkg/authn"
)

type EntityType uint8

const (
	UserEntity EntityType = iota
	GroupEntity
	ClientEntity
	ChannelEntity
)

// String representation of the possible entity type values.
const (
	userEntityType    = "user"
	groupEntityType   = "group"
	clientEntityType  = "client"
	channelEntityType = "channel"
)

// String converts entity type to string literal.
func (e EntityType) String() string {
	switch e {
	case UserEntity:
		return userEntityType
	case GroupEntity:
		return groupEntityType
	case ClientEntity:
		return clientEntityType
	case ChannelEntity:
		return channelEntityType
	default:
		return ""
	}
}

// ToEntityType converts string value to a valid entity type.
func ToEntityType(entityType string) (EntityType, error) {
	switch entityType {
	case userEntityType:
		return UserEntity, nil
	case groupEntityType:
		return GroupEntity, nil
	case clientEntityType:
		return ClientEntity, nil
	case channelEntityType:
		return ChannelEntity, nil
	default:
		return EntityType(0), apiutil.ErrInvalidEntityType
	}
}

// Query returns the SQL condition for the entity type.
func (e EntityType) Query() string {
	switch e {
	case UserEntity:
		return "((operation LIKE 'user.%' AND attributes->>'id' = :entity_id) OR (attributes->>'user_id' = :entity_id))"
	case GroupEntity:
		return "((operation LIKE 'group.%' AND (attributes->>'id' = :entity_id OR attributes->>'entity_id' = :entity_id)))"
	case ChannelEntity:
		return "((operation LIKE 'channel.%' AND (attributes->>'id' = :entity_id OR attributes->>'entity_id' = :entity_id)) OR (jsonb_exists_any(attributes->'channel_ids', array[:entity_id])))"
	case ClientEntity:
		return "((operation LIKE 'client.%' AND (attributes->>'id' = :entity_id OR attributes->>'entity_id' = :entity_id)) OR (jsonb_exists_any(attributes->'client_ids', array[:entity_id])))"
	default:
		return ""
	}
}

// Journal represents an event journal that occurred in the system.
type Journal struct {
	ID         string         `json:"id,omitempty" db:"id"`
	Domain     string         `json:"domain,omitempty" db:"domain"`
	Operation  string         `json:"operation,omitempty" db:"operation,omitempty"`
	OccurredAt time.Time      `json:"occurred_at,omitempty" db:"occurred_at,omitempty"`
	Attributes map[string]any `json:"attributes,omitempty" db:"attributes,omitempty"` // This is extra information about the journal for example client_id, user_id, group_id etc.
	Metadata   map[string]any `json:"metadata,omitempty" db:"metadata,omitempty"`     // This is decoded metadata from the journal.
}

// JournalsPage represents a page of journals.
type JournalsPage struct {
	Total    uint64    `json:"total"`
	Offset   uint64    `json:"offset"`
	Limit    uint64    `json:"limit"`
	Journals []Journal `json:"journals"`
}

// Page is used to filter journals.
type Page struct {
	Offset         uint64     `json:"offset" db:"offset"`
	Limit          uint64     `json:"limit" db:"limit"`
	Operation      string     `json:"operation,omitempty" db:"operation,omitempty"`
	From           time.Time  `json:"from,omitempty" db:"from,omitempty"`
	To             time.Time  `json:"to,omitempty" db:"to,omitempty"`
	WithAttributes bool       `json:"with_attributes,omitempty"`
	WithMetadata   bool       `json:"with_metadata,omitempty"`
	EntityID       string     `json:"entity_id,omitempty" db:"entity_id,omitempty"`
	EntityType     EntityType `json:"entity_type,omitempty" db:"entity_type,omitempty"`
	Direction      string     `json:"direction,omitempty"`
}

func (page JournalsPage) MarshalJSON() ([]byte, error) {
	type Alias JournalsPage
	a := struct {
		Alias
	}{
		Alias: Alias(page),
	}

	if a.Journals == nil {
		a.Journals = make([]Journal, 0)
	}

	return json.Marshal(a)
}

type ClientTelemetry struct {
	ClientID         string    `json:"client_id"`
	DomainID         string    `json:"domain_id"`
	Subscriptions    uint64    `json:"subscriptions"`
	InboundMessages  uint64    `json:"inbound_messages"`
	OutboundMessages uint64    `json:"outbound_messages"`
	FirstSeen        time.Time `json:"first_seen"`
	LastSeen         time.Time `json:"last_seen"`
}

type ClientSubscription struct {
	ID           string `json:"id" db:"id"`
	SubscriberID string `json:"subscriber_id" db:"subscriber_id"`
	ChannelID    string `json:"channel_id" db:"channel_id"`
	Subtopic     string `json:"subtopic" db:"subtopic"`
	ClientID     string `json:"client_id" db:"client_id"`
}

// Service provides access to the journal log service.
type Service interface {
	// Save saves the journal to the database.
	Save(ctx context.Context, journal Journal) error

	// RetrieveAll retrieves all journals from the database with the given page.
	RetrieveAll(ctx context.Context, session smqauthn.Session, page Page) (JournalsPage, error)

	// RetrieveClientTelemetry retrieves telemetry data for a client.
	RetrieveClientTelemetry(ctx context.Context, session smqauthn.Session, clientID string) (ClientTelemetry, error)
}

// Repository provides access to the journal log database.
type Repository interface {
	// Save persists the journal to a database.
	Save(ctx context.Context, journal Journal) error

	// RetrieveAll retrieves all journals from the database with the given page.
	RetrieveAll(ctx context.Context, page Page) (JournalsPage, error)

	// SaveClientTelemetry persists telemetry data for a client to the database.
	SaveClientTelemetry(ctx context.Context, ct ClientTelemetry) error

	// RetrieveClientTelemetry retrieves telemetry data for a client from the database.
	RetrieveClientTelemetry(ctx context.Context, clientID, domainID string) (ClientTelemetry, error)

	// DeleteClientTelemetry removes telemetry data for a client from the database.
	DeleteClientTelemetry(ctx context.Context, clientID, domainID string) error

	// AddSubscription adds a subscription to the client telemetry.
	AddSubscription(ctx context.Context, sub ClientSubscription) error

	// CountSubscriptions returns the number of subscriptions for a client.
	CountSubscriptions(ctx context.Context, clientID string) (uint64, error)

	// RemoveSubscription removes a subscription from the client telemetry.
	RemoveSubscription(ctx context.Context, subscriberID string) error

	// IncrementInboundMessages increments the inbound messages count for a client.
	IncrementInboundMessages(ctx context.Context, ct ClientTelemetry) error

	// IncrementOutboundMessages increments the outbound messages count for a client.
	IncrementOutboundMessages(ctx context.Context, channelID, subtopic string) error
}