package chronograf

import (
	"context"
	"net/http"
	"time"
)

// General errors.
const (
	ErrUpstreamTimeout     = Error("request to backend timed out")
	ErrExplorationNotFound = Error("exploration not found")
	ErrSourceNotFound      = Error("source not found")
	ErrServerNotFound      = Error("server not found")
	ErrLayoutNotFound      = Error("layout not found")
	ErrAlertNotFound       = Error("alert not found")
	ErrAuthentication      = Error("user not authenticated")
)

// Error is a domain error encountered while processing chronograf requests
type Error string

func (e Error) Error() string {
	return string(e)
}

// Logger represents an abstracted structured logging implementation. It
// provides methods to trigger log messages at various alert levels and a
// WithField method to set keys for a structured log message.
type Logger interface {
	Debug(...interface{})
	Info(...interface{})
	Warn(...interface{})
	Error(...interface{})
	Fatal(...interface{})
	Panic(...interface{})

	WithField(string, interface{}) Logger
}

// Assets returns a handler to serve the website.
type Assets interface {
	Handler() http.Handler
}

// TimeSeries represents a queryable time series database.
type TimeSeries interface {
	// Query retrieves time series data from the database.
	Query(context.Context, Query) (Response, error)
	// Connect will connect to the time series using the information in `Source`.
	Connect(context.Context, *Source) error
}

// Query retrieves a Response from a TimeSeries.
type Query struct {
	Command string `json:"query"` // Command is the query itself
	DB      string `json:"db"`    // DB is optional and if empty will not be used.
	RP      string `json:"rp"`    // RP is a retention policy and optional; if empty will not be used.
}

// Response is the result of a query against a TimeSeries
type Response interface {
	MarshalJSON() ([]byte, error)
}

// Source is connection information to a time-series data store.
type Source struct {
	ID       int    `json:"id,omitempty,string"` // ID is the unique ID of the source
	Name     string `json:"name"`                // Name is the user-defined name for the source
	Type     string `json:"type,omitempty"`      // Type specifies which kinds of source (enterprise vs oss)
	Username string `json:"username,omitempty"`  // Username is the username to connect to the source
	Password string `json:"password,omitempty"`  // Password is in CLEARTEXT // TODO: fixme
	URL      string `json:"url"`                 // URL are the connections to the source
	Default  bool   `json:"default"`             // Default specifies the default source for the application
}

// SourcesStore stores connection information for a `TimeSeries`
type SourcesStore interface {
	// All returns all sources in the store
	All(context.Context) ([]Source, error)
	// Add creates a new source in the SourcesStore and returns Source with ID
	Add(context.Context, Source) (Source, error)
	// Delete the Source from the store
	Delete(context.Context, Source) error
	// Get retrieves Source if `ID` exists
	Get(ctx context.Context, ID int) (Source, error)
	// Update the Source in the store.
	Update(context.Context, Source) error
}

// AlertRule represents rules for building a tickscript alerting task
type AlertRule struct {
	ID            string        `json:"id,omitempty"` // ID is the unique ID of the alert
	Query         QueryConfig   `json:"query"`        // Query is the filter of data for the alert.
	Every         string        `json:"every"`        // Every how often to check for the alerting criteria
	Alerts        []string      `json:"alerts"`       // AlertServices name all the services to notify (e.g. pagerduty)
	Message       string        `json:"message"`      // Message included with alert
	Trigger       string        `json:"trigger"`      // Trigger is a type that defines when to trigger the alert
	TriggerValues TriggerValues `json:"values"`       // Defines the values that cause the alert to trigger
	Name          string        `json:"name"`         // Name is the user-defined name for the alert
}

// AlertRulesStore stores rules for building tickscript alerting tasks
type AlertRulesStore interface {
	// All returns all rules in the store
	All(context.Context) ([]AlertRule, error)
	// Add creates a new rule in the AlertRulesStore and returns AlertRule with ID
	Add(context.Context, AlertRule) (AlertRule, error)
	// Delete the AlertRule from the store
	Delete(context.Context, AlertRule) error
	// Get retrieves AlertRule if `ID` exists
	Get(ctx context.Context, ID string) (AlertRule, error)
	// Update the AlertRule in the store.
	Update(context.Context, AlertRule) error
}

// TICKScript task to be used by kapacitor
type TICKScript string

// Ticker generates tickscript tasks for kapacitor
type Ticker interface {
	// Generate will create the tickscript to be used as a kapacitor task
	Generate(AlertRule) (TICKScript, error)
}

// TriggerValues specifies the alerting logic for a specific trigger type
type TriggerValues struct {
	Change     string `json:"change,omitempty"`     // Change specifies if the change is a percent or absolute
	Period     string `json:"period,omitempty"`     // Period is the window to search for alerting criteria
	Shift      string `json:"shift,omitempty"`      // Shift is the amount of time to look into the past for the alert to compare to the present
	Operator   string `json:"operator,omitempty"`   // Operator for alert comparison
	Value      string `json:"value,omitempty"`      // Value is the boundary value when alert goes critical
	Percentile string `json:"percentile,omitempty"` // Percentile is defined only when Relation is not "Once"
	Relation   string `json:"relation,omitempty"`   // Relation defines the logic about how often the threshold is met to be an alert.
}

// QueryConfig represents UI query from the data explorer
type QueryConfig struct {
	ID              string `json:"id,omitempty"`
	Database        string `json:"database"`
	Measurement     string `json:"measurement"`
	RetentionPolicy string `json:"retentionPolicy"`
	Fields          []struct {
		Field string   `json:"field"`
		Funcs []string `json:"funcs"`
	} `json:"fields"`
	Tags    map[string][]string `json:"tags"`
	GroupBy struct {
		Time string   `json:"time"`
		Tags []string `json:"tags"`
	} `json:"groupBy"`
	AreTagsAccepted bool   `json:"areTagsAccepted"`
	RawText         string `json:"rawText,omitempty"`
}

// Server represents a proxy connection to an HTTP server
type Server struct {
	ID       int    // ID is the unique ID of the server
	SrcID    int    // SrcID of the data source
	Name     string // Name is the user-defined name for the server
	Username string // Username is the username to connect to the server
	Password string // Password is in CLEARTEXT // TODO: FIXME
	URL      string // URL are the connections to the server
}

// ServersStore stores connection information for a `Server`
type ServersStore interface {
	// All returns all servers in the store
	All(context.Context) ([]Server, error)
	// Add creates a new source in the ServersStore and returns Server with ID
	Add(context.Context, Server) (Server, error)
	// Delete the Server from the store
	Delete(context.Context, Server) error
	// Get retrieves Server if `ID` exists
	Get(ctx context.Context, ID int) (Server, error)
	// Update the Server in the store.
	Update(context.Context, Server) error
}

// ID creates uniq ID string
type ID interface {
	// Generate creates a unique ID string
	Generate() (string, error)
}

// UserID is a unique ID for a source user.
type UserID int

// User represents an authenticated user.
type User struct {
	ID   UserID
	Name string
}

// AuthStore is the Storage and retrieval of authentication information
type AuthStore struct {
	// User management for the AuthStore
	Users interface {
		// Create a new User in the AuthStore
		Add(context.Context, User) error
		// Delete the User from the AuthStore
		Delete(context.Context, User) error
		// Retrieve a user if `ID` exists.
		Get(ctx context.Context, ID int) error
		// Update the user's permissions or roles
		Update(context.Context, User) error
	}
}

// ExplorationID is a unique ID for an Exploration.
type ExplorationID int

// Exploration is a serialization of front-end Data Explorer.
type Exploration struct {
	ID        ExplorationID
	Name      string    // User provided name of the Exploration.
	UserID    UserID    // UserID is the owner of this Exploration.
	Data      string    // Opaque blob of JSON data.
	CreatedAt time.Time // Time the exploration was first created.
	UpdatedAt time.Time // Latest time the exploration was updated.
	Default   bool      // Flags an exploration as the default.
}

// ExplorationStore stores front-end serializations of data explorer sessions.
type ExplorationStore interface {
	// Search the ExplorationStore for each Exploration owned by `UserID`.
	Query(ctx context.Context, userID UserID) ([]*Exploration, error)
	// Create a new Exploration in the ExplorationStore.
	Add(context.Context, *Exploration) (*Exploration, error)
	// Delete the Exploration from the ExplorationStore.
	Delete(context.Context, *Exploration) error
	// Retrieve an Exploration if `ID` exists.
	Get(ctx context.Context, ID ExplorationID) (*Exploration, error)
	// Update the Exploration; will also update the `UpdatedAt` time.
	Update(context.Context, *Exploration) error
}

// Cell is a rectangle and multiple time series queries to visualize.
type Cell struct {
	X       int32   `json:"x"`
	Y       int32   `json:"y"`
	W       int32   `json:"w"`
	H       int32   `json:"h"`
	I       string  `json:"i"`
	Name    string  `json:"name"`
	Queries []Query `json:"queries"`
}

// Layout is a collection of Cells for visualization
type Layout struct {
	ID          string `json:"id"`
	Application string `json:"app"`
	Measurement string `json:"measurement"`
	Cells       []Cell `json:"cells"`
}

// LayoutStore stores dashboards and associated Cells
type LayoutStore interface {
	// All returns all dashboards in the store
	All(context.Context) ([]Layout, error)
	// Add creates a new dashboard in the LayoutStore
	Add(context.Context, Layout) (Layout, error)
	// Delete the dashboard from the store
	Delete(context.Context, Layout) error
	// Get retrieves Layout if `ID` exists
	Get(ctx context.Context, ID string) (Layout, error)
	// Update the dashboard in the store.
	Update(context.Context, Layout) error
}

// Principal is any entity that can be authenticated
type Principal string

// PrincipalKey is used to pass principal
// via context.Context to request-scoped
// functions.
const PrincipalKey Principal = "principal"

// Authenticator represents a service for authenticating users.
type Authenticator interface {
	// Authenticate returns User associated with token if successful.
	Authenticate(ctx context.Context, token string) (Principal, error)
	// Token generates a valid token for Principal lasting a duration
	Token(context.Context, Principal, time.Duration) (string, error)
}

// TokenExtractor extracts tokens from http requests
type TokenExtractor interface {
	// Extract will return the token or an error.
	Extract(r *http.Request) (string, error)
}