package main

import (
	"errors"
	"strings"
)

// DefaultUnavailableMessage is the Tier-2 fallback shown when an online booking
// can't be completed for a reason the visitor can't fix (our auth/config, a
// Cal.com 5xx, a network timeout, or anything we don't recognise). It is the
// default both for the admin-authored block field (booking.templ / the editor's
// textarea default) AND for the handler's fallback when that field is left
// blank, so the two never drift. Admins can override it per block.
const DefaultUnavailableMessage = "Sorry — we couldn't complete your booking online. Please use our contact form and we'll get you booked in."

// Tier-1 curated, user-actionable booking-error copy. Each names the actual
// problem the visitor can act on. The raw Cal.com message is NEVER surfaced —
// these strings are all the visitor ever sees. canRetry decides whether the
// error renders with the "Try again" reset control (true only when picking a
// different slot/time is the fix).
const (
	msgSlotUnavailable   = "Sorry, that time isn't available anymore. Please choose another slot."
	msgEventFullyBooked  = "This event is fully booked right now. Please try a different time."
	msgInvalidPhone      = "That phone number doesn't look valid — please check it and try again."
	msgInvalidGuestEmail = "One or more guest email addresses are invalid — please check them."
	msgRejectedAnswer    = "One of your answers wasn't accepted — please review the form and try again."
)

// bookingErrorResult is the curated, visitor-facing outcome of classifying a
// CreateBooking failure: the message to render and whether to offer the
// retry/reset control.
type bookingErrorResult struct {
	message  string
	canRetry bool
}

// classifyBookingError maps a CreateBooking failure to curated visitor copy.
//
// Tier 1 (user-fixable) → a specific, actionable message, with canRetry=true
// where re-picking a slot/time is the fix. Tier 2 (our-side / non-fixable:
// auth/config 401-403, Cal.com 5xx, network/timeout, or anything unrecognised)
// → the admin-authored adminMessage (already defaulted to
// DefaultUnavailableMessage by the caller when blank).
//
// Cal.com's booking endpoint does NOT return a discriminating error.code — live
// probing (2026-06-21) showed every 400 carrying a generic "BadRequestException"
// or "BAD_REQUEST". The real signal is the message text, so classification is
// driven by case-insensitive substring matching on Status + Message, with Code
// only as a coarse gate. The raw Cal.com message never reaches the visitor.
func classifyBookingError(err error, adminMessage string) bookingErrorResult {
	tier2 := bookingErrorResult{message: adminMessage, canRetry: false}

	var apiErr *CalcomAPIError
	if !errors.As(err, &apiErr) {
		// Network/transport error (DNS, timeout, connection reset) — no HTTP
		// response came back. Not the visitor's to fix.
		return tier2
	}

	// 401/403/5xx are our side (bad/expired API key, Cal.com outage). Anything
	// outside the user-error band (HTTP 400 / 409 / 422) is Tier 2 too.
	switch {
	case apiErr.Status == 401 || apiErr.Status == 403:
		return tier2
	case apiErr.Status >= 500:
		return tier2
	case apiErr.Status != 400 && apiErr.Status != 409 && apiErr.Status != 422:
		return tier2
	}

	msg := strings.ToLower(apiErr.Message)
	switch {
	// Slot gone: in the past, already taken, host no longer available. All
	// recoverable by choosing another slot → render WITH the reset control.
	case containsAny(msg, "in the past", "not available", "no longer available",
		"already has booking", "already booked", "slot", "no_available_users",
		"already_booked", "booking_seats_full_error", "host"):
		return bookingErrorResult{message: msgSlotUnavailable, canRetry: true}

	// Event-level capacity exhausted (distinct copy; still time-recoverable).
	case containsAny(msg, "booking_limit", "fully booked", "no more slots",
		"limit reached", "exceeded", "sold out"):
		return bookingErrorResult{message: msgEventFullyBooked, canRetry: true}

	// Bad attendee phone number (Cal.com: "{attendeePhoneNumber} invalid_number").
	case containsAny(msg, "invalid_number", "phone"):
		return bookingErrorResult{message: msgInvalidPhone, canRetry: false}

	// Invalid guest email(s). Live probe: "responses - {guests}email_validation_error".
	case strings.Contains(msg, "guest"):
		return bookingErrorResult{message: msgInvalidGuestEmail, canRetry: false}

	// A rejected custom-field answer. "responses" / "bookingfields" signal a
	// per-field validation rejection; render generic-but-actionable copy.
	// (We do not echo Cal.com's field token — it isn't safe curated text.)
	case containsAny(msg, "responses", "bookingfields", "booking field",
		"required", "email_validation_error", "validation"):
		return bookingErrorResult{message: msgRejectedAnswer, canRetry: false}
	}

	// Recognised as a 400-class API error but no signal we can map to specific,
	// safe copy → admin-authored message (never Cal.com's raw text).
	return tier2
}

// containsAny reports whether s contains any of the given (already
// lower-cased) substrings.
func containsAny(s string, subs ...string) bool {
	for _, sub := range subs {
		if strings.Contains(s, sub) {
			return true
		}
	}
	return false
}