package process

import (
	"encoding/json"
	"fmt"

	"github.com/nats-io/nats.go"

	"git.novox.be/novox/mesh-sdk/go/announce"
)

// Keeps says on the bus, as this process's module, every state it keeps and which of them others may read (novox/hq
// ADR 0495 clause 2; issue 1790), on announce.Subject; what a reader is granted is what the owner announced (clause 3).
// It publishes at once and again after every reconnect, so the controller hears it whenever it missed it. From then on
// a state of the module that it did not announce is refused at the call, naming it, so code and announcement cannot
// drift (clause 5). It refuses a state no bucket could be named by and a state given twice.
func (c *Conn) Keeps(states ...announce.State) error {
	if err := c.remember(states); err != nil {
		return err
	}
	c.mu.Lock()
	first := !c.reannounces
	c.reannounces = true
	c.mu.Unlock()
	if first {
		before := c.nc.Opts.ReconnectedCB
		c.nc.SetReconnectHandler(func(nc *nats.Conn) {
			if before != nil {
				before(nc)
			}
			_ = c.publishKeeps()
		})
	}
	return c.publishKeeps()
}

// remember makes the announcement of states and binds only them from now on.
func (c *Conn) remember(states []announce.State) error {
	data, err := announce.Encode(announce.States{Module: c.account.Module, Node: c.account.Node, States: states})
	if err != nil {
		return err
	}
	names := map[string]bool{}
	for _, s := range states {
		names[s.Name] = true
	}
	c.mu.Lock()
	c.kept, c.announced = names, data
	c.mu.Unlock()
	return nil
}

func (c *Conn) publishKeeps() error {
	c.mu.Lock()
	data := c.announced
	c.mu.Unlock()
	if err := c.Emit(announce.Event, json.RawMessage(data)); err != nil {
		return fmt.Errorf("announcing what %s keeps: %w", c.account.Module, err)
	}
	return nil
}

// refusedUnannounced is the error of a bind of a state Keeps did not name, or nil (also before Keeps).
func (c *Conn) refusedUnannounced(name string) error {
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.kept != nil && !c.kept[name] {
		return fmt.Errorf("the state %q is not among the states %s announced it keeps (Conn.Keeps)", name, c.account.Module)
	}
	return nil
}