package support

import (
	"context"
	"errors"
	"log/slog"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
)

// TryAutoReplyLLM is the ONLY intended entry point for LLM-assisted ticket
// replies using platformsettings.AIRoleSupport / aiprovider.RoleSupport.
//
// Security gates (always applied):
//   - context deadline (AutoReplyTimeout)
//   - per-company + platform AI rate limits
//   - ticket load scoped by id (company_id captured for prompt isolation)
//   - skip when auto_reply_disabled / already posted / closed
//
// LLM completion remains product-gated: until a SupportAIRunner is configured
// on Service (agent 4 wiring), this returns ErrAIAutoReplyDisabled after gates.
// Create / ReplyAsUser / ReplyAsAgent must not call a Completer directly.
//
// Guided /docs Ask remains rule-based and must never use AIRoleSupport.
func (s *Service) TryAutoReplyLLM(ctx context.Context, ticketID uuid.UUID) error {
	if s == nil {
		return ErrAIAutoReplyDisabled
	}
	ctx, cancel := context.WithTimeout(ctx, AutoReplyTimeout)
	defer cancel()

	companyID, err := s.loadTicketCompanyForAuto(ctx, ticketID)
	if err != nil {
		return err
	}

	// Fail closed before claim/rate-limit consume when no runner is wired.
	if s.SupportAI == nil {
		return ErrAIAutoReplyDisabled
	}

	limiter := s.aiLimiter()
	if !limiter.Allow(companyID) {
		slog.Info("support_auto_ai_rate_limited",
			"ticket_id", ticketID.String(),
			"company_id", companyID.String(),
		)
		_ = s.markAutoHandOff(ctx, ticketID)
		return ErrAIRateLimited
	}

	claim, err := s.ClaimAutoReplyAttempt(ctx, ticketID)
	if err != nil {
		if errors.Is(err, ErrAutoReplyAlreadyPosted) ||
			errors.Is(err, ErrAutoReplyDisabled) ||
			errors.Is(err, ErrTicketClosed) {
			return err
		}
		if errors.Is(err, context.DeadlineExceeded) || errors.Is(ctx.Err(), context.DeadlineExceeded) {
			return ErrAIAutoReplyTimeout
		}
		return err
	}
	runCtx, runCancel := context.WithTimeout(ctx, AutoReplyTimeout)
	defer runCancel()
	err = s.SupportAI.RunAutoReply(runCtx, s, claim)
	if err != nil {
		if errors.Is(err, context.DeadlineExceeded) || errors.Is(runCtx.Err(), context.DeadlineExceeded) {
			slog.Warn("support_auto_ai_timeout",
				"ticket_id", ticketID.String(),
				"company_id", companyID.String(),
				"err", RedactForAutoLog(err.Error()),
			)
			_ = s.markAutoHandOff(ctx, ticketID)
			return ErrAIAutoReplyTimeout
		}
		if errors.Is(err, ErrAIAutoReplyDisabled) ||
			errors.Is(err, ErrAutoReplyAlreadyPosted) ||
			errors.Is(err, ErrAutoReplyDisabled) ||
			errors.Is(err, ErrTicketClosed) {
			return err
		}
		slog.Warn("support_auto_ai_failed",
			"ticket_id", ticketID.String(),
			"company_id", companyID.String(),
			"err", RedactForAutoLog(err.Error()),
		)
		// Runner may have already handed off; ensure claimable human queue.
		_ = s.markAutoHandOff(ctx, ticketID)
		return err
	}
	return nil
}

// SupportAIRunner performs the LLM call + draft/send after security gates pass.
// Implemented by agent 4; nil keeps TryAutoReplyLLM refuse-by-default.
type SupportAIRunner interface {
	RunAutoReply(ctx context.Context, svc *Service, claim AutoClaim) error
}

func (s *Service) aiLimiter() *AIRateLimiter {
	if s != nil && s.AIRateLimiter != nil {
		return s.AIRateLimiter
	}
	return AIRateLimiterDefault()
}

func (s *Service) loadTicketCompanyForAuto(ctx context.Context, ticketID uuid.UUID) (uuid.UUID, error) {
	if s == nil || s.Pool == nil {
		return uuid.Nil, ErrAIAutoReplyDisabled
	}
	var companyID uuid.UUID
	err := s.Pool.QueryRow(ctx, `
		SELECT company_id FROM support_tickets WHERE id = $1`, ticketID,
	).Scan(&companyID)
	if errors.Is(err, pgx.ErrNoRows) {
		return uuid.Nil, ErrNotFound
	}
	return companyID, err
}