// Package provision creates the rows a new customer needs before anything else
// works: a client, a site with its broker identity, staff logins, and the
// one-shot codes their PCs enrol with.
//
// It is a command, not an API. Creating a tenant is rare, needs database
// access anyway to add the matching Mosquitto user, and an HTTP endpoint that
// mints tenants is a much larger thing to have to secure than a subcommand
// that only runs on the box.
package provision

import (
	"context"
	"crypto/rand"
	"encoding/base32"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"

	"github.com/jackc/pgx/v5"

	"github.com/loyaly/behavision-server/internal/auth"
	"github.com/loyaly/behavision-server/internal/secret"
)

type Provisioner struct {
	Pool    *pgxpool.Pool
	Secrets *secret.Box
	// Broker registers a site's login with Mosquitto when set. Without it the
	// command prints the password for a hand edit of the passwd file, which
	// is the pre-dynamic-security fallback and nothing more.
	Broker SiteBroker
}

// SiteBroker mirrors internal/broker's interface without importing it.
type SiteBroker interface {
	EnsureSite(ctx context.Context, username, password string) error
}

func (p *Provisioner) CreateClient(ctx context.Context, slug, name string) (string, error) {
	slug = strings.ToLower(strings.TrimSpace(slug))
	var id string
	err := p.Pool.QueryRow(ctx, `
		INSERT INTO clients (slug, name) VALUES ($1, $2)
		ON CONFLICT (slug) DO UPDATE SET name = EXCLUDED.name
		RETURNING id::text`, slug, name).Scan(&id)
	return id, err
}

// SiteResult carries the broker credential exactly once. It is stored
// encrypted and never returned by any HTTP route, so this is the only moment
// the plaintext exists outside the enrolment response.
type SiteResult struct {
	SiteID   string
	AgentID  string
	Username string
	Password string
	// BrokerRegistered is true when the login was pushed to Mosquitto here,
	// so nothing remains for a person to type.
	BrokerRegistered bool
}

// CreateSite makes a site, its agent row, and the broker password.
//
// The password is generated here rather than typed: it is never memorised by
// anyone, it goes into Mosquitto's passwd file and into this database sealed,
// and a human-chosen one would only be weaker.
func (p *Provisioner) CreateSite(ctx context.Context, clientSlug, siteSlug, name, tz string) (
	SiteResult, error) {

	var out SiteResult
	if p.Secrets == nil {
		return out, errors.New("BEHAVISION_SECRET_KEY must be set to create a site")
	}
	clientSlug = strings.ToLower(strings.TrimSpace(clientSlug))
	siteSlug = strings.ToLower(strings.TrimSpace(siteSlug))
	if tz == "" {
		tz = "UTC"
	}
	if _, err := time.LoadLocation(tz); err != nil {
		return out, fmt.Errorf("unknown timezone %q", tz)
	}

	var clientID string
	if err := p.Pool.QueryRow(ctx,
		`SELECT id::text FROM clients WHERE slug = $1`, clientSlug).
		Scan(&clientID); err != nil {
		return out, fmt.Errorf("no client %q: %w", clientSlug, err)
	}

	tx, err := p.Pool.Begin(ctx)
	if err != nil {
		return out, err
	}
	defer tx.Rollback(ctx) //nolint:errcheck

	if err := tx.QueryRow(ctx, `
		INSERT INTO sites (client_id, slug, name, timezone)
		VALUES ($1, $2, $3, $4)
		ON CONFLICT (client_id, slug) DO UPDATE
		    SET name = EXCLUDED.name, timezone = EXCLUDED.timezone
		RETURNING id::text`, clientID, siteSlug, name, tz).
		Scan(&out.SiteID); err != nil {
		return out, fmt.Errorf("create site: %w", err)
	}

	// The username IS the MQTT topic prefix, enforced by the broker's
	// `pattern write bv/%u/...`. It must match contract.ParseTopic's
	// <client>.<site> shape exactly or the server cannot resolve the tenant.
	out.Username = clientSlug + "." + siteSlug
	if err := tx.QueryRow(ctx, `
		INSERT INTO agents (client_id, site_id, mqtt_username)
		VALUES ($1, $2::uuid, $3)
		ON CONFLICT (site_id) DO UPDATE SET mqtt_username = EXCLUDED.mqtt_username
		RETURNING id::text`, clientID, out.SiteID, out.Username).
		Scan(&out.AgentID); err != nil {
		return out, fmt.Errorf("create agent: %w", err)
	}

	out.Password, err = randomSecret(24)
	if err != nil {
		return out, err
	}
	sealed, err := p.Secrets.SealString(out.Password, out.AgentID)
	if err != nil {
		return out, err
	}
	if _, err := tx.Exec(ctx,
		`UPDATE agents SET mqtt_password_enc = $2 WHERE id = $1::uuid`,
		out.AgentID, sealed); err != nil {
		return out, err
	}
	if err := tx.Commit(ctx); err != nil {
		return out, err
	}
	if p.Broker != nil {
		if err := p.Broker.EnsureSite(ctx, out.Username, out.Password); err != nil {
			return out, fmt.Errorf("site %s created, but the broker did not accept its login: %w", out.Username, err)
		}
		out.BrokerRegistered = true
	}
	return out, nil
}

func (p *Provisioner) CreateUser(ctx context.Context, clientSlug, email, role,
	fullName, password string) (string, string, error) {

	email = auth.NormalizeEmail(email)
	if email == "" {
		return "", "", errors.New("email is required")
	}
	switch role {
	case "owner", "manager", "staff", "admin":
	default:
		return "", "", fmt.Errorf("role must be owner, manager, staff or admin")
	}
	if role == "admin" && clientSlug != "" {
		// A platform admin is defined by having no client. Letting one be
		// created inside a tenant would produce an account whose scope depends
		// on which query happens to check first.
		return "", "", errors.New("an admin has no client - omit -client")
	}
	if role != "admin" && clientSlug == "" {
		return "", "", errors.New("-client is required for this role")
	}

	if password == "" {
		var err error
		if password, err = randomSecret(16); err != nil {
			return "", "", err
		}
	}
	hash, err := auth.HashPassword(password)
	if err != nil {
		return "", "", err
	}

	var clientID any
	if clientSlug != "" {
		var id string
		if err := p.Pool.QueryRow(ctx,
			`SELECT id::text FROM clients WHERE slug = $1`,
			strings.ToLower(clientSlug)).Scan(&id); err != nil {
			return "", "", fmt.Errorf("no client %q: %w", clientSlug, err)
		}
		clientID = id
	}

	// Upsert, because resetting a forgotten password is the other reason this
	// command exists. The WHERE is what keeps that from being a way to hijack
	// an account: an address is unique across the whole platform now, so
	// without it `provision user -client acme -email someone@..` would quietly
	// take an existing platform admin - or another company's owner - and
	// rewrite their password and role, leaving the row attached to its
	// original client.
	var id string
	err = p.Pool.QueryRow(ctx, `
		INSERT INTO app_users (client_id, email, password_hash, full_name, role)
		VALUES ($1::uuid, $2, $3, $4, $5)
		ON CONFLICT (lower(email))
		DO UPDATE SET password_hash = EXCLUDED.password_hash,
		              full_name     = EXCLUDED.full_name,
		              role          = EXCLUDED.role,
		              active        = true
		WHERE app_users.client_id IS NOT DISTINCT FROM EXCLUDED.client_id
		RETURNING id::text`, clientID, email, hash, fullName, role).Scan(&id)
	if errors.Is(err, pgx.ErrNoRows) {
		return "", "", fmt.Errorf("%s already has an account in another company "+
			"(or is a platform admin); one address is one account", email)
	}
	return id, password, err
}

// IssueEnrolmentToken mints the code an installer types once.
//
// Short-lived on purpose: it is read aloud, pasted into chat and photographed,
// and it is the only thing standing between a stranger and a site's broker
// credentials. A week is long enough to get an engineer to a shop.
func (p *Provisioner) IssueEnrolmentToken(ctx context.Context, clientSlug,
	siteSlug, label string, ttl time.Duration) (string, time.Time, error) {

	if ttl <= 0 {
		ttl = 7 * 24 * time.Hour
	}
	var clientID, siteID string
	if err := p.Pool.QueryRow(ctx, `
		SELECT c.id::text, si.id::text
		FROM sites si JOIN clients c ON c.id = si.client_id
		WHERE c.slug = $1 AND si.slug = $2`,
		strings.ToLower(clientSlug), strings.ToLower(siteSlug)).
		Scan(&clientID, &siteID); err != nil {
		return "", time.Time{}, fmt.Errorf("no site %s/%s: %w",
			clientSlug, siteSlug, err)
	}

	code, err := auth.NewEnrolmentCode()
	if err != nil {
		return "", time.Time{}, err
	}
	expires := time.Now().Add(ttl).UTC()
	if _, err := p.Pool.Exec(ctx, `
		INSERT INTO site_enrolment_tokens (client_id, site_id, token_hash,
		                                   label, expires_at)
		VALUES ($1::uuid, $2::uuid, $3, $4, $5)`,
		clientID, siteID, auth.HashToken(auth.NormalizeCode(code)),
		label, expires); err != nil {
		return "", time.Time{}, err
	}
	return code, expires, nil
}

func randomSecret(n int) (string, error) {
	b := make([]byte, n)
	if _, err := rand.Read(b); err != nil {
		return "", err
	}
	// base32 without padding: this gets typed, pasted into config files and
	// read down a phone line, and base64's + / = survive none of that.
	return strings.ToLower(base32.StdEncoding.
		WithPadding(base32.NoPadding).EncodeToString(b)), nil
}

// enrolmentCode is grouped for reading aloud. The hyphens are cosmetic - the
// handler strips them before hashing - so an operator who types it without
// them still gets in.