package registry

import (
	"crypto/rand"
	"database/sql"
	"encoding/hex"
	"errors"
)

var ErrTimerChanged = errors.New("registry: timer registration changed")

// UpsertTimerRegistration compares the captured registration and returns the
// resulting registration in the same transaction. Empty means absent at read.
func (r *Registry) UpsertTimerRegistration(t Timer, expected string) (*Timer, error) {
	if r.remote != nil {
		out, err := r.remote.call(nil, remoteRequest{Method: "UpsertTimerRegistration", T: t, Expected: expected}, nil)
		return out.Timer, err
	}

	tx, err := r.sql.Begin()
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()
	old, err := scanTimer(tx.QueryRow(`SELECT `+timerCols+` FROM timers WHERE host=? AND name=?`, t.Host, t.Name))
	if errors.Is(err, sql.ErrNoRows) {
		if expected != "" {
			return nil, ErrTimerChanged
		}
	} else if err != nil {
		return nil, err
	} else {
		if old.Kind != t.Kind {
			return nil, ErrTimerKind
		}
		if expected == "" || old.Registration != expected {
			return nil, ErrTimerChanged
		}
	}
	rt, err := scanRoute(tx.QueryRow(`SELECT `+routeCols+` FROM routes WHERE host=?`, t.Host).Scan)
	if err != nil && !errors.Is(err, sql.ErrNoRows) {
		return nil, err
	}
	if err == nil && rt.ClaimOwnership.Valid() {
		if t.ClaimOwner != "" && (t.ClaimIncarnation != rt.ClaimIncarnation || t.ClaimStamp != rt.ClaimStamp || t.ClaimOwner != rt.ClaimOwner) {
			return nil, ErrClaimOwnership
		}
		t.ClaimOwnership = rt.ClaimOwnership
	}
	var id [16]byte
	if _, err = rand.Read(id[:]); err != nil {
		return nil, err
	}
	t.Registration = hex.EncodeToString(id[:])
	if t.ClaimOwnership.Valid() {
		t.ClaimRowID = t.Registration
	}
	if err = upsertTimer(tx, t); err != nil {
		return nil, err
	}
	row, err := scanTimer(tx.QueryRow(`SELECT `+timerCols+` FROM timers WHERE host=? AND name=?`, t.Host, t.Name))
	if err != nil {
		return nil, err
	}
	if err := tx.Commit(); err != nil {
		return nil, err
	}
	return &row, nil
}

func (r *Registry) SetTimerStatusRegistration(host, name, registration, status string) error {
	if r.remote != nil {
		_, err := r.remote.call(nil, remoteRequest{Method: "SetTimerStatusRegistration", Host: host, Name: name, Registration: registration, Status: status}, nil)
		return err
	}

	if registration == "" {
		return ErrTimerChanged
	}
	res, err := r.sql.Exec(`UPDATE timers SET last_status=? WHERE host=? AND name=? AND registration=?`, status, host, name, registration)
	return timerRegistrationResult(res, err)
}

func (r *Registry) FireTimerNowRegistration(host, name, registration string, now int64) error {
	if r.remote != nil {
		_, err := r.remote.call(nil, remoteRequest{Method: "FireTimerNowRegistration", Host: host, Name: name, Registration: registration, Now: now}, nil)
		return err
	}

	if registration == "" {
		return ErrTimerChanged
	}
	var id [16]byte
	if _, err := rand.Read(id[:]); err != nil {
		return err
	}
	next := hex.EncodeToString(id[:])
	res, err := r.sql.Exec(`UPDATE timers SET next_at=?, due_at=?, attempts=0, registration=?, claim_row_id=CASE WHEN claim_owner='' THEN claim_row_id ELSE ? END WHERE host=? AND name=? AND registration=?`, now, now, next, next, host, name, registration)
	return timerRegistrationResult(res, err)
}

func timerRegistrationResult(res sql.Result, err error) error {
	if err != nil {
		return err
	}
	n, err := res.RowsAffected()
	if err == nil && n == 0 {
		return ErrTimerChanged
	}
	return err
}