package main

import (
	"errors"
	"strings"
)

type publishingPolicy interface {
	defaultStatus() string
	isAllowedStatus(status string) bool
	invalidStatusMessage() string
	validate(payload Doc, existing Doc) error
}

func applyPublishingPolicy(payload Doc, partial bool, existing Doc, policy publishingPolicy) error {
	status, hasStatus, err := getOptionalString(payload, "status")
	if err != nil {
		return errors.New("status must be a string")
	}
	if !hasStatus && !partial {
		status = policy.defaultStatus()
		hasStatus = true
	}
	if hasStatus {
		normalizedStatus := strings.TrimSpace(strings.ToLower(status))
		if !policy.isAllowedStatus(normalizedStatus) {
			return errors.New(policy.invalidStatusMessage())
		}
		payload["status"] = normalizedStatus
	}

	return policy.validate(payload, existing)
}

func mergedPublishingValue(payload Doc, existing Doc, field string) (any, bool) {
	if value, ok := payload[field]; ok {
		return value, true
	}
	if existing == nil {
		return nil, false
	}
	value, ok := existing[field]
	return value, ok
}

func mergedPublishingString(payload Doc, existing Doc, field string) (string, bool) {
	value, ok := mergedPublishingValue(payload, existing, field)
	if !ok {
		return "", false
	}
	text, ok := value.(string)
	if !ok {
		return "", false
	}
	trimmed := strings.TrimSpace(text)
	if trimmed == "" {
		return "", false
	}
	return strings.ToLower(trimmed), true
}