// Package tryevent is what the checker says on its stream checks when a whole try (a try of a delivery group, not narrowed
// to a level or to some tests) starts and ends (issue 1921), and what the indexer, which hears it, reads: a try has no pull
// request, so the indexer writes the candidate of its group from the members at their commits, and deletes it at the end.
// The events carry the members, so no part reads the checker's state.
package tryevent

import (
	"encoding/json"
	"fmt"
	"regexp"
)

// The events of the checker's stream checks.
const (
	Started = "try.started"
	Ended   = "try.ended"
)

// IDOK is the shape of a try's id, which is also the name of its group (the key of its candidate).
var IDOK = regexp.MustCompile(`^try-[0-9]{1,20}$`)

// Member is one repository of the try: the exact commit and the trunk commit it is merged onto.
type Member struct {
	Repository string `json:"repository"`
	Head       string `json:"head"`
	Trunk      string `json:"trunk"`
}

// Event is the body of both events: the try, and for Started its members; for Ended the state it ended in.
type Event struct {
	ID      string   `json:"id"`
	Members []Member `json:"members,omitempty"`
	State   string   `json:"state,omitempty"`
}

// Decode reads an event body; a started event names its members.
func Decode(event string, body []byte) (Event, error) {
	var e Event
	if err := json.Unmarshal(body, &e); err != nil {
		return e, err
	}
	if !IDOK.MatchString(e.ID) {
		return e, fmt.Errorf("%q is not a try's id, try-<digits>", e.ID)
	}
	if event == Started && len(e.Members) == 0 {
		return e, fmt.Errorf("the try %s starts with no member", e.ID)
	}
	return e, nil
}

// Open is one try that waits or runs, as the checker's tool checker_tries answers it.
type Open struct {
	ID      string   `json:"id"`
	State   string   `json:"state"`
	Whole   bool     `json:"whole"`
	Members []Member `json:"members"`
}