using System.Globalization;
using System.Text.RegularExpressions;
using HrynCo.NotificationService.Contracts.Messages;
using HrynCo.NotificationService.DAL.Abstract.Templates;

namespace HrynCo.NotificationService.Worker.Services.Push;

public static partial class PushTemplateRenderer
{
    public static RenderedPushMessageData Render(PushTemplateDefinition template, SendPushMessageData message)
    {
        if (message.Version != 2 || !PushMessageValidator.IsValidContent(message))
            throw new EmailTemplateWriteException("Invalid version 2 push template data.", false);
        var data = message.TemplateData!;
        var language = template.Languages.SingleOrDefault(l => l.LanguageCode == message.LanguageCode)
            ?? template.Languages.SingleOrDefault(l => l.LanguageCode == "en")
            ?? throw new EmailTemplateWriteException("Push template language and English fallback are missing.", false);
        PushTemplateValidation.Validate(template);
        ValidateRequiredBindings(template, data.Bindings);
        var actions = PushTemplateActionValidation.Parse(language.ActionsJson);
        return new RenderedPushMessageData(message,
            RenderText(language.Title, data.Bindings, 100),
            RenderText(language.Body, data.Bindings, 500),
            actions.DefaultAction is null ? null : ResolveAction(actions.DefaultAction, null, data),
            actions.Buttons.Select(b => ResolveAction(b.Action,
                RenderText(b.Label, data.Bindings, 100), data)).ToList());
    }

    private static void ValidateRequiredBindings(PushTemplateDefinition template, IReadOnlyDictionary<string, string> bindings)
    {
        foreach (var variable in template.Variables.Where(v => v.Required))
            if (!bindings.TryGetValue(variable.Name, out var value) || string.IsNullOrWhiteSpace(value))
                throw new EmailTemplateWriteException("A required push binding is missing.", false);
    }

    private static RenderedPushAction ResolveAction(string key, string? label, PushTemplateData data)
    {
        if (!data.Actions.TryGetValue(key, out var metadata) || metadata is null)
            throw new EmailTemplateWriteException("A configured push action is missing from message metadata.", false);
        return new RenderedPushAction(key, metadata.ObjectId, label);
    }

    private static string RenderText(string template, IReadOnlyDictionary<string, string> bindings, int limit)
    {
        var value = Placeholder().Replace(template, match => bindings.GetValueOrDefault(match.Groups[1].Value) ?? "");
        if (string.IsNullOrWhiteSpace(value))
            throw new EmailTemplateWriteException("Rendered push text is empty.", false);
        if (value.Length <= limit) return value;
        var starts = StringInfo.ParseCombiningCharacters(value);
        var end = starts.LastOrDefault(offset => offset <= limit - 1);
        return value[..end] + "…";
    }

    [GeneratedRegex(@"\{\{([^{}]+)\}\}")]
    private static partial Regex Placeholder();
}