package payments

import (
	"context"
	"errors"
	"net/http"

	"crussell/internal/square"
)

// chargeFailureStatus classifies a SquareClient.CreatePayment error into the
// HTTP status a payment handler should return:
//
//   - 503 (Service Unavailable) for AMBIGUOUS failures: transport/network
//     errors, Square 5xx responses, context cancellation/deadline, and the
//     retryable 4xx statuses 429 (rate limited), 408 (request timeout), and
//     425 (too early) — the money state at Square is unknown, so the frontend
//     should treat it as a retry (the pending record is resumed on a same-key
//     retry). Square's own docs treat 429 as "retry later"; mapping it (or a
//     timeout/early request) to 402 would mislabel a retryable condition as a
//     permanent decline.
//   - 402 (Payment Required) for DEFINITIVE declines: a structured Square
//     error (squareAPIError) carrying any OTHER 4xx status (400/402/422 etc.)
//     means Square positively rejected the charge (card declined/expired,
//     AVS/CVV failure) — retrying with the same inputs cannot succeed.
//
// A nil error is never expected (callers only invoke this on the error path);
// it maps to 402 defensively. The dev mock returns plain errors for simulated
// failures, which classify as 503 (ambiguous) — correct for a mock standing in
// for an unreachable Square.
func chargeFailureStatus(err error) int {
	if err == nil {
		return http.StatusPaymentRequired
	}
	if errors.Is(err, context.DeadlineExceeded) || errors.Is(err, context.Canceled) {
		return http.StatusServiceUnavailable
	}
	status := square.ErrorStatusCode(err)
	if status == 0 || status >= 500 {
		return http.StatusServiceUnavailable
	}
	// Retryable/ambiguous 4xx carve-outs: 429 (RATE_LIMITED), 408 (request
	// timeout), and 425 (too early) are not definitive declines — Square's
	// docs tell clients to retry later. Classify them as 503 so the pending
	// record stays resumable on a same-key retry instead of being labelled a
	// permanent decline. True declines (400/402/422 etc.) fall through to 402.
	if status == http.StatusTooManyRequests || status == http.StatusRequestTimeout || status == http.StatusTooEarly {
		return http.StatusServiceUnavailable
	}
	if status >= 400 && status < 500 {
		return http.StatusPaymentRequired
	}
	return http.StatusServiceUnavailable
}