package common

import (
	stdlib_context "context"
	"sync"
	"time"
)

type Config interface {
	Name() string
	Starter() StartFct
	Children() []Config
	Add(Config)
}

type Message interface{}

type Services map[string]Context

type ContextState interface{}

type Context interface {
	stdlib_context.Context
	Config() Config
	Parent() Context
	Services() Services
	ChildContext(Config) Context
	State() ContextState
	WithState(ContextState) Context
	Mailbox() chan Message
	WaitGroup() *sync.WaitGroup
	Stop()
}

type FctCtx = func(Context)

type StartFct = FctCtx

// async Runners

func RunCtx(ctx Context, fct FctCtx) {
	ctx.WaitGroup().Add(1)
	go func() {
		defer ctx.WaitGroup().Done()
		fct(ctx)
	}()
}

// Context implementation

type context struct {
	cfg      Config
	parent   Context
	children []Context
	state    ContextState
	mailbox  chan Message
}

func (ctx *context) Config() Config {
	return ctx.cfg
}

func (ctx *context) Parent() Context {
	return ctx.parent
}

func (ctx *context) Services() Services {
	return ctx.parent.Services()
}

func (ctx *context) ChildContext(cfg Config) Context {
	cctx := makeCtx(cfg, ctx)
	ctx.Services()[cfg.Name()] = cctx
	ctx.children = append(ctx.children, cctx)
	return cctx
}

func (ctx *context) State() ContextState {
	return ctx.state
}

func (ctx *context) WithState(state ContextState) Context {
	ctx.state = state
	return ctx
}

func (ctx *context) Mailbox() chan Message {
	return ctx.mailbox
}

func (ctx *context) WaitGroup() *sync.WaitGroup {
	return ctx.parent.WaitGroup()
}

func (ctx *context) Done() <-chan struct{} {
	return ctx.parent.Done()
}

func (ctx *context) Stop() {
	// ctx.Warn("Only application-level service can be stopped
}

func makeCtx(cfg Config, parent Context) *context {
	return &context{
		cfg:     cfg,
		parent:  parent,
		mailbox: make(chan Message, 10),
	}
}

// top-level application context

type appContext struct {
	*context
	services  Services
	waitgroup *sync.WaitGroup
	doneCh    chan struct{}
}

func (ctx *appContext) ChildContext(cfg Config) Context {
	cctx := makeCtx(cfg, ctx)
	ctx.services[cfg.Name()] = cctx
	ctx.children = append(ctx.children, cctx)
	return cctx
}

func (ctx *appContext) Services() Services {
	return ctx.services
}

func (ctx *appContext) WithState(state ContextState) Context {
	ctx.state = state
	return ctx
}

func (ctx *appContext) WaitGroup() *sync.WaitGroup {
	return ctx.waitgroup
}

func (ctx *appContext) Done() <-chan struct{} {
	return ctx.doneCh
}

func (ctx *appContext) Stop() {
	close(ctx.doneCh)
}

func AppContext(cfg Config) Context {
	ctx := &appContext{
		context:   makeCtx(cfg, nil),
		services:  Services{},
		waitgroup: &sync.WaitGroup{},
		doneCh:    make(chan struct{}),
	}
	ctx.services[cfg.Name()] = ctx
	return ctx
}

// implement interface context.Context from standard library

func (ctx *context) Deadline() (deadline time.Time, ok bool) {
	return time.Time{}, false
}

func (ctx *context) Err() error {
	select {
	case _, ok := <-ctx.Done():
		if !ok {
			return stdlib_context.Canceled
		}
	default:
		return nil
	}
	return nil
}

func (ctx *context) Value(key interface{}) interface{} {
	return nil
}