package slack

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"net/http"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgconn"
	"github.com/jackc/pgx/v5/pgtype"

	"github.com/multica-ai/multica/server/internal/integrations/channel/engine"
	"github.com/multica-ai/multica/server/internal/util/secretbox"
	db "github.com/multica-ai/multica/server/pkg/db/generated"
)

// This file is the Slack install backend (MUL-3666). Slack uses the
// bring-your-own-app (BYO) model: the workspace admin creates their own Slack
// app, installs it to their Slack workspace, and pastes its bot token (xoxb-) +
// app-level token (xapp-) into Multica (the paste path lives in byo_install.go).
// The InstallService owns the at-rest encryption of those tokens — so no caller
// can write a channel_installation with a plaintext token — plus the shared
// persistInstall transaction and the list / get / revoke management surface.

var (
	// ErrInstallationNotFound surfaces "no row matches in this workspace".
	ErrInstallationNotFound = errors.New("slack installation not found")
	// ErrTeamOwnedByAnotherWorkspace is returned when the pasted Slack app is
	// already connected to a live owner in a DIFFERENT Multica workspace — it
	// would collide with the (channel_type, app_id) routing index. A Slack app is
	// one bot identity and maps to one agent; reusing it here requires
	// disconnecting it in the other workspace first.
	ErrTeamOwnedByAnotherWorkspace = errors.New("slack: this Slack app is already connected to a different Multica workspace")
	// ErrTeamOwnedBySameWorkspace is returned when the app is already connected to
	// a DIFFERENT (live, non-archived) agent in the SAME workspace. The old
	// catch-all wrongly blamed "another workspace"; naming the same-workspace case
	// points the user at the Disconnect they can actually reach (#4810).
	ErrTeamOwnedBySameWorkspace = errors.New("slack: this Slack app is already connected to another agent in this workspace")
	// ErrTeamOwnedByArchivedAgent is returned when the app's owning agent is
	// archived (and so still holds the bot, since archiving is reversible). The
	// user recovers by restoring that agent or disconnecting its bot.
	ErrTeamOwnedByArchivedAgent = errors.New("slack: this Slack app is connected to an archived agent in this workspace")
)

// installQueries is the slice of generated queries InstallService needs. WithTx
// returns the same interface bound to a transaction so persistInstall runs its
// upsert atomically (and so tests can inject a fake without a real DB).
type installQueries interface {
	WithTx(tx pgx.Tx) installQueries
	UpsertChannelInstallation(ctx context.Context, arg db.UpsertChannelInstallationParams) (db.ChannelInstallation, error)
	ReclaimDeadChannelInstallationByAppID(ctx context.Context, arg db.ReclaimDeadChannelInstallationByAppIDParams) (pgtype.UUID, error)
	GetChannelInstallationOwnerByAppID(ctx context.Context, arg db.GetChannelInstallationOwnerByAppIDParams) (db.GetChannelInstallationOwnerByAppIDRow, error)
	ListChannelInstallationsByWorkspace(ctx context.Context, arg db.ListChannelInstallationsByWorkspaceParams) ([]db.ChannelInstallation, error)
	GetChannelInstallationInWorkspace(ctx context.Context, arg db.GetChannelInstallationInWorkspaceParams) (db.ChannelInstallation, error)
	SetChannelInstallationStatus(ctx context.Context, arg db.SetChannelInstallationStatusParams) error
}

// dbInstallQueries adapts *db.Queries to installQueries — the generated WithTx
// returns *db.Queries, so we wrap it to return the interface (the same adapter
// pattern engine.ChatSession uses).
type dbInstallQueries struct{ *db.Queries }

func (q dbInstallQueries) WithTx(tx pgx.Tx) installQueries {
	return dbInstallQueries{q.Queries.WithTx(tx)}
}

// InstallService owns the at-rest encryption of the bot + app tokens (so no
// caller can write a channel_installation with a plaintext token) and the shared
// install transaction. The box MUST be non-nil (we refuse plaintext storage even
// in dev).
type InstallService struct {
	box        *secretbox.Box
	q          installQueries
	tx         engine.TxStarter
	httpClient *http.Client
	logger     *slog.Logger

	// apiURL overrides the Slack API base for the BYO auth.test call (tests point
	// it at an httptest server). Empty uses the real Slack API.
	apiURL string
}

// NewInstallService binds the service to queries, a tx starter (*pgxpool.Pool),
// and an encryption box. Listing / revoking and BYO register all require only
// the box (the at-rest key); there is no hosted OAuth credential.
func NewInstallService(q *db.Queries, tx engine.TxStarter, box *secretbox.Box, logger *slog.Logger) (*InstallService, error) {
	if q == nil {
		return nil, errors.New("slack: InstallService requires queries")
	}
	return newInstallService(dbInstallQueries{q}, tx, box, logger)
}

// newInstallService is the testable core: it takes the installQueries interface
// so tests can inject a fake (with a fake TxStarter) without a real DB.
func newInstallService(q installQueries, tx engine.TxStarter, box *secretbox.Box, logger *slog.Logger) (*InstallService, error) {
	if box == nil {
		return nil, errors.New("slack: InstallService requires a non-nil secretbox.Box")
	}
	if q == nil {
		return nil, errors.New("slack: InstallService requires queries")
	}
	if tx == nil {
		return nil, errors.New("slack: InstallService requires a tx starter")
	}
	if logger == nil {
		logger = slog.Default()
	}
	return &InstallService{
		box:        box,
		q:          q,
		tx:         tx,
		httpClient: http.DefaultClient,
		logger:     logger,
	}, nil
}

// installPersist carries the resolved fields persistInstall writes. appIDKey is
// the value stored at config->>'app_id' — the real Slack app id — and MUST equal
// the app_id inside configJSON; it is the lookup / ON CONFLICT key. installerSlackID
// is the installer's Slack user id to auto-bind, or "" to skip (a BYO paste
// carries no authed_user, so the installer binds via the normal token flow on
// first message).
type installPersist struct {
	wsID        pgtype.UUID
	agentID     pgtype.UUID
	installerID pgtype.UUID
	// appIDKey is the Slack app id stored at config->>'app_id'; it MUST equal the
	// app_id inside configJSON. It keys the dead-owner reclaim and the live-owner
	// lookup that drives the accurate conflict message.
	appIDKey string
	// configJSON holds the Slack app id (config->>'app_id') used for inbound
	// routing; the ROW itself is keyed by (workspace, agent) — one bot per agent.
	configJSON []byte
}

// pgUniqueViolation is the Postgres SQLSTATE for a unique-constraint violation.
const pgUniqueViolation = "23505"

// persistInstall upserts the installation keyed by (workspace_id, agent_id,
// channel_type): ONE Slack bot per agent. Re-connecting an agent — including
// swapping it to a NEW Slack app after a disconnect — UPDATES that agent's row
// in place instead of colliding with the (workspace, agent, channel) unique.
//
// The (channel_type, app_id) routing index is the only OTHER unique constraint,
// and it is NOT this upsert's conflict target, so a unique violation here means
// the pasted Slack app is already connected to a DIFFERENT agent or Multica
// workspace — refuse it (ErrTeamOwnedByAnotherWorkspace) rather than steal it.
// No chat-session retire is needed: a row's agent_id never changes (it is part
// of the key), so existing sessions stay valid for the same agent.
func (s *InstallService) persistInstall(ctx context.Context, p installPersist) (db.ChannelInstallation, error) {
	tx, err := s.tx.Begin(ctx)
	if err != nil {
		return db.ChannelInstallation{}, fmt.Errorf("begin install tx: %w", err)
	}
	defer func() { _ = tx.Rollback(ctx) }()
	qtx := s.q.WithTx(tx)

	// Free the (slack, app_id) routing slot from any DEAD prior owner — a revoked
	// placeholder, or an orphan whose owning workspace/agent was deleted (#4810) —
	// before the upsert, so a bot whose old owner is gone can be rebound. A live
	// owner (active agent, including an archived one) is left in place and trips
	// the unique index below, which we turn into an accurate conflict.
	if _, err := qtx.ReclaimDeadChannelInstallationByAppID(ctx, db.ReclaimDeadChannelInstallationByAppIDParams{
		ChannelType: string(TypeSlack),
		AppID:       p.appIDKey,
		WorkspaceID: p.wsID,
		AgentID:     p.agentID,
	}); err != nil && !errors.Is(err, pgx.ErrNoRows) {
		// pgx.ErrNoRows just means nothing was dead — a no-op, not a failure.
		return db.ChannelInstallation{}, fmt.Errorf("reclaim dead slack installation: %w", err)
	}

	inst, err := qtx.UpsertChannelInstallation(ctx, db.UpsertChannelInstallationParams{
		WorkspaceID:     p.wsID,
		AgentID:         p.agentID,
		ChannelType:     string(TypeSlack),
		Config:          p.configJSON,
		InstallerUserID: p.installerID,
	})
	if err != nil {
		var pgErr *pgconn.PgError
		if errors.As(err, &pgErr) && pgErr.Code == pgUniqueViolation {
			return db.ChannelInstallation{}, s.liveOwnerConflictErr(ctx, p.wsID, p.appIDKey)
		}
		return db.ChannelInstallation{}, fmt.Errorf("upsert slack installation: %w", err)
	}
	if err := tx.Commit(ctx); err != nil {
		return db.ChannelInstallation{}, fmt.Errorf("commit slack install: %w", err)
	}
	return inst, nil
}

// liveOwnerConflictErr classifies who holds the (slack, app_id) routing slot
// after the dead-owner reclaim ran, so persistInstall returns a sentinel the
// handler renders as an accurate message rather than the old catch-all that
// always blamed "another workspace" (#4810). Read on the base pool (s.q), since
// the failed upsert has aborted the tx. A now-free slot (concurrent disconnect)
// or lookup error falls back to the generic cross-workspace sentinel — a retry
// then succeeds.
func (s *InstallService) liveOwnerConflictErr(ctx context.Context, requestingWorkspaceID pgtype.UUID, appID string) error {
	owner, err := s.q.GetChannelInstallationOwnerByAppID(ctx, db.GetChannelInstallationOwnerByAppIDParams{
		ChannelType: string(TypeSlack),
		AppID:       appID,
	})
	if err != nil {
		return ErrTeamOwnedByAnotherWorkspace
	}
	switch {
	case owner.WorkspaceID != requestingWorkspaceID:
		return ErrTeamOwnedByAnotherWorkspace
	case owner.AgentArchivedAt.Valid:
		return ErrTeamOwnedByArchivedAgent
	default:
		return ErrTeamOwnedBySameWorkspace
	}
}

// ListByWorkspace returns every Slack installation in the workspace (active and
// revoked), for the management surface.
func (s *InstallService) ListByWorkspace(ctx context.Context, wsID pgtype.UUID) ([]db.ChannelInstallation, error) {
	return s.q.ListChannelInstallationsByWorkspace(ctx, db.ListChannelInstallationsByWorkspaceParams{
		WorkspaceID: wsID,
		ChannelType: string(TypeSlack),
	})
}

// GetInWorkspace is the workspace-scoped lookup so a forged installation id from
// another workspace returns NotFound instead of leaking existence.
func (s *InstallService) GetInWorkspace(ctx context.Context, id, wsID pgtype.UUID) (db.ChannelInstallation, error) {
	inst, err := s.q.GetChannelInstallationInWorkspace(ctx, db.GetChannelInstallationInWorkspaceParams{
		ID:          id,
		WorkspaceID: wsID,
		ChannelType: string(TypeSlack),
	})
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return db.ChannelInstallation{}, ErrInstallationNotFound
		}
		return db.ChannelInstallation{}, err
	}
	return inst, nil
}

// Revoke flips status to 'revoked'. The row is preserved for audit; a re-install
// flips it back to 'active'. The Supervisor stops supervising the installation
// (ListActiveInstallations filters to active), so its Socket Mode connection
// winds down, and outbound drops too.
func (s *InstallService) Revoke(ctx context.Context, id pgtype.UUID) error {
	return s.q.SetChannelInstallationStatus(ctx, db.SetChannelInstallationStatusParams{
		ID:     id,
		Status: "revoked",
	})
}