using AIStudio.Chat;
using AIStudio.Settings;
using AIStudio.Settings.DataModel;
using AIStudio.Tools.PluginSystem;
using AIStudio.Tools.PluginSystem.Assistants;
using AIStudio.Tools.ToolCallingSystem;
using ProviderSettings = AIStudio.Settings.Provider;

namespace AIStudio.Tools.Services;

public sealed class DirectChatService(SettingsManager settingsManager, DataSourceService dataSourceService, ToolRegistry toolRegistry, ILogger<DirectChatService> logger)
{
    private static string TB(string fallbackEn) => I18N.I.T(fallbackEn, typeof(DirectChatService).Namespace, nameof(DirectChatService));

    public async Task<DirectChatStartResult> TryCreateAssistantChatAsync(PluginAssistants assistantPlugin)
    {
        if (assistantPlugin.ChatLaunchConfiguration is not { } launchConfiguration)
            return new(null, TB("The assistant plugin does not contain a valid chat launch configuration."));

        var providerResult = this.ResolveProvider(launchConfiguration.ProviderId);
        if (providerResult.IsExplicit && providerResult.Provider == ProviderSettings.NONE)
            return new(null, providerResult.ErrorMessage);

        var profileResult = this.ResolveProfile(launchConfiguration.ProfileId);
        var profile = profileResult.Profile;
        if (profile is null)
            return new(null, profileResult.ErrorMessage);

        var chatTemplateResult = this.ResolveChatTemplate(launchConfiguration.ChatTemplateId);
        var chatTemplate = chatTemplateResult.ChatTemplate;
        if (chatTemplate is null)
            return new(null, chatTemplateResult.ErrorMessage);

        //
        // A chat template that forbids profiles wins over a configured profile: the chat disables
        // its profile selection for such templates, so keeping the profile would pin one that the
        // user can neither see nor change. We drop it instead of failing the whole launch.
        //
        if (!chatTemplate.AllowProfileUsage && profile != Profile.NO_PROFILE)
        {
            logger.LogWarning(
                "Assistant plugin '{PluginName}' selects the profile '{ProfileName}', but its chat template '{ChatTemplateName}' does not allow profiles. The chat starts without a profile.",
                assistantPlugin.Name, profile.GetSafeName(), chatTemplate.GetSafeName());

            profile = Profile.NO_PROFILE;
        }

        var dataSourceOptionsResult = await this.ResolveDataSourceOptionsAsync(assistantPlugin, providerResult.Provider, chatTemplate, launchConfiguration.DataSourceIds);
        var dataSourceOptions = dataSourceOptionsResult.Options;
        if (dataSourceOptions is null)
            return new(null, dataSourceOptionsResult.ErrorMessage);

        //
        // A launcher that names no workspace wants the same chat the chat page starts on its own:
        // one that belongs nowhere, is kept among the temporary chats, and disappears with them. The
        // empty workspace ID is what says so, here as everywhere else in the app.
        //
        var workspaceId = Guid.Empty;
        if (!launchConfiguration.OpensTemporaryChat)
        {
            try
            {
                workspaceId = await WorkspaceBehaviour.ResolveOrCreateWorkspaceIdByNameAsync(launchConfiguration.WorkspaceName);
            }
            catch (Exception exception)
            {
                logger.LogError(exception, "Assistant plugin '{PluginName}' could not resolve or create workspace '{WorkspaceName}'.", assistantPlugin.Name, launchConfiguration.WorkspaceName);
                return new(null, string.Format(TB("The workspace '{0}' could not be opened or created."), launchConfiguration.WorkspaceName));
            }

            if (workspaceId == Guid.Empty)
            {
                logger.LogWarning("Assistant plugin '{PluginName}' could not resolve or create workspace '{WorkspaceName}'.", assistantPlugin.Name, launchConfiguration.WorkspaceName);
                return new(null, string.Format(TB("The workspace '{0}' could not be opened or created."), launchConfiguration.WorkspaceName));
            }
        }

        var toolChoice = ChatTemplate.ChooseToolIds(chatTemplate, launchConfiguration.ToolIds);
        if (toolChoice.LauncherChoiceDropped)
            logger.LogWarning(
                "Assistant plugin '{PluginName}' selects the tools '{LauncherToolIds}', but its chat template '{ChatTemplateName}' names tools of its own. The chat starts with the tools of that template.",
                assistantPlugin.Name, string.Join(", ", launchConfiguration.ToolIds!), chatTemplate.GetSafeName());

        //
        // Only the tools the user could have switched on themselves. Either side may name one whose
        // settings are incomplete — an unconfigured web search, say — and starting the chat with it
        // enabled would show a state the user cannot produce by hand and cannot fix from the chat.
        // Null keeps the chat's own defaults, which is what a launcher without tools wants.
        //
        var selectedToolIds = toolChoice.ToolIds is null
            ? null
            : await toolRegistry.FilterSelectableToolIdsAsync(Components.CHAT, toolChoice.ToolIds);

        var chatThread = new ChatThread
        {
            IncludeDateTime = true,
            SelectedProvider = providerResult.Provider == ProviderSettings.NONE ? string.Empty : providerResult.Provider.Id,
            SelectedProfile = profile.Id,
            SelectedChatTemplate = chatTemplate.Id,
            // The provider confidence is checked later, when the chat sends a message:
            SelectedToolIds = selectedToolIds,
            SystemPrompt = SystemPrompts.DEFAULT,
            WorkspaceId = workspaceId,
            ChatId = Guid.NewGuid(),
            Name = assistantPlugin.AssistantTitle,
            DataSourceOptions = dataSourceOptions,
            Blocks = chatTemplate == ChatTemplate.NO_CHAT_TEMPLATE ? [] : chatTemplate.ExampleConversation.Select(block => block.DeepClone()).ToList(),
        };

        //
        // Whoever decided these options — the chat template or the launcher — decided them for this
        // chat. Without saying so, the chat page would replace them with the chat defaults again:
        //
        var dataSourcesWereChosen = chatTemplate.DataSourceOptions is not null || launchConfiguration.DataSourceIds is not null;
        return new(new(chatThread, ApplySelectedChatTemplateToComposer: true, PreserveDataSourceOptions: dataSourcesWereChosen), string.Empty);
    }

    private (ProviderSettings Provider, bool IsExplicit, string ErrorMessage) ResolveProvider(Guid? providerId)
    {
        //
        // The launcher does not name a provider, so it wants the chat defaults. We resolve them
        // exactly like the chat does when it loads a chat without a provider. When no default can
        // be determined, we do not fail: the chat opens with an empty provider selection and the
        // user picks a provider there, just like for any other new chat.
        //
        if (providerId is null)
            return new(settingsManager.GetChatProviderForLoadedChat(), false, string.Empty);

        //
        // GetProviderById does not apply any confidence filtering, so we check the provider
        // ourselves afterwards, exactly as its documentation demands:
        //
        var provider = settingsManager.GetProviderById(providerId.Value.ToString());
        if (provider == ProviderSettings.NONE)
            return new(ProviderSettings.NONE, true, string.Format(TB("The assistant chat launcher references provider '{0}', but that provider does not exist."), providerId));

        if (!settingsManager.IsProviderConfident(provider, Components.CHAT))
            return new(ProviderSettings.NONE, true, string.Format(TB("The provider '{0}' selected by the assistant chat launcher is not permitted for chats at the required confidence level."), provider.InstanceName));

        return new(provider, true, string.Empty);
    }

    private (Profile? Profile, string ErrorMessage) ResolveProfile(Guid? profileId)
    {
        if (profileId is null)
            return new(settingsManager.GetPreselectedProfile(Components.CHAT), string.Empty);

        // The launcher explicitly wants no profile:
        if (profileId == Guid.Empty)
            return new(Profile.NO_PROFILE, string.Empty);

        //
        // We already handled the empty GUID above, so GetProfileById returning the no-profile
        // entry here can only mean that the referenced profile is gone:
        //
        var profile = settingsManager.GetProfileById(profileId.Value.ToString());
        return profile == Profile.NO_PROFILE
            ? new(null, string.Format(TB("The assistant chat launcher references profile '{0}', but that profile does not exist."), profileId))
            : new(profile, string.Empty);
    }

    private (ChatTemplate? ChatTemplate, string ErrorMessage) ResolveChatTemplate(Guid? chatTemplateId)
    {
        if (chatTemplateId is null)
            return new(settingsManager.GetPreselectedChatTemplate(Components.CHAT), string.Empty);

        // The launcher explicitly wants no chat template:
        if (chatTemplateId == Guid.Empty)
            return new(ChatTemplate.NO_CHAT_TEMPLATE, string.Empty);

        //
        // We already handled the empty GUID above, so GetChatTemplateById returning the
        // no-template entry here can only mean that the referenced template is gone:
        //
        var chatTemplate = settingsManager.GetChatTemplateById(chatTemplateId.Value.ToString());
        return chatTemplate == ChatTemplate.NO_CHAT_TEMPLATE
            ? new(null, string.Format(TB("The assistant chat launcher references chat template '{0}', but that template does not exist."), chatTemplateId))
            : new(chatTemplate, string.Empty);
    }

    private async Task<(DataSourceOptions? Options, string ErrorMessage)> ResolveDataSourceOptionsAsync(PluginAssistants assistantPlugin, ProviderSettings provider, ChatTemplate chatTemplate, IReadOnlyList<Guid>? launcherDataSourceIds)
    {
        //
        // The launcher names data sources as plain IDs, and the options around them are always the
        // same ones. Building them here turns its choice into the same kind of thing the chat
        // template carries, which is what lets one rule decide between the two.
        //
        DataSourceOptions? launcherOptions = null;
        if (launcherDataSourceIds is not null)
        {
            var standardOptions = settingsManager.ConfigurationData.Chat.PreselectedDataSourceOptions;
            launcherOptions = new DataSourceOptions
            {
                DisableDataSources = false,
                AutomaticDataSourceSelection = false,
                AutomaticValidation = standardOptions.AutomaticValidation,
                PreselectedDataSourceIds = launcherDataSourceIds.Select(dataSourceId => dataSourceId.ToString()).ToList(),
            };
        }

        var optionsChoice = ChatTemplate.ChooseDataSourceOptions(chatTemplate, launcherOptions);
        if (optionsChoice.LauncherChoiceDropped)
            logger.LogWarning(
                "Assistant plugin '{PluginName}' selects the data sources '{LauncherDataSourceIds}', but its chat template '{ChatTemplateName}' brings data source options of its own. The chat starts with the data sources of that template.",
                assistantPlugin.Name, string.Join(", ", launcherDataSourceIds!), chatTemplate.GetSafeName());

        // Neither side says anything, so the chat starts the way it would start on its own:
        if (optionsChoice.Options is not { } chosenOptions)
            return new(settingsManager.ConfigurationData.Chat.PreselectedDataSourceOptions.CreateCopy(), string.Empty);

        return await this.CheckChosenDataSourcesAsync(provider, chosenOptions, chatTemplate.DataSourceOptions is null ? null : chatTemplate);
    }

    /// <summary>
    /// Checks that the chosen data sources exist and may be used with the provider of the chat.
    /// </summary>
    /// <remarks>
    /// Opening a launcher is one click, so a source which is gone or not permitted has to be said
    /// out loud instead of being dropped quietly: nobody would see what the chat is missing. Which
    /// of the two sides chose the sources changes nothing but the wording — and that wording is the
    /// only place where the user learns which of them to go and fix.
    /// </remarks>
    /// <param name="provider">The provider the launched chat runs with.</param>
    /// <param name="chosenOptions">The options the chat is about to start with.</param>
    /// <param name="originChatTemplate">The chat template the options came from, or null when the launcher named the sources itself.</param>
    /// <returns>The checked options, or null and a message saying why no chat was created.</returns>
    private async Task<(DataSourceOptions? Options, string ErrorMessage)> CheckChosenDataSourcesAsync(ProviderSettings provider, DataSourceOptions chosenOptions, ChatTemplate? originChatTemplate)
    {
        //
        // There is nothing to check when data sources are switched off, and nothing to check either
        // when an agent picks them: that choice is made per message in the chat, exactly as it is
        // for a chat template the user picks by hand.
        //
        if (chosenOptions.DisableDataSources || chosenOptions.AutomaticDataSourceSelection || chosenOptions.PreselectedDataSourceIds.Count == 0)
            return new(chosenOptions, string.Empty);

        //
        // Deciding which data sources are permitted needs an effective provider. Without one,
        // the check below would report every requested source as unavailable, which would hide
        // the actual cause from the user:
        //
        if (provider == ProviderSettings.NONE)
            return new(null, originChatTemplate is null
                ? TB("The assistant chat launcher selects data sources, but no provider is available for chats. Please choose a default provider for chats first. No chat was created.")
                : string.Format(TB("The chat template '{0}' selects data sources, but no provider is available for chats. Please choose a default provider for chats first. No chat was created."), originChatTemplate.GetSafeName()));

        var requestedDataSources = new List<IDataSource>(chosenOptions.PreselectedDataSourceIds.Count);
        foreach (var dataSourceId in chosenOptions.PreselectedDataSourceIds)
        {
            // Data sources have no lookup helper in the settings manager, so we match their ids
            // the same way the rest of the app does:
            var dataSource = settingsManager.ConfigurationData.DataSources.FirstOrDefault(candidate =>
                string.Equals(candidate.Id, dataSourceId, StringComparison.OrdinalIgnoreCase));

            if (dataSource is null)
                return new(null, originChatTemplate is null
                    ? string.Format(TB("The assistant chat launcher references data source '{0}', but that data source does not exist."), dataSourceId)
                    : string.Format(TB("The chat template '{0}' references data source '{1}', but that data source does not exist."), originChatTemplate.GetSafeName(), dataSourceId));

            requestedDataSources.Add(dataSource);
        }

        //
        // The IDs are written back from the sources they resolved to: one of them may be spelled in
        // another case than the source itself, and the chat matches its preselection literally.
        //
        chosenOptions.PreselectedDataSourceIds = requestedDataSources.Select(source => source.Id).ToList();

        IReadOnlyList<IDataSource> availableDataSources;
        try
        {
            //
            // The options the launched chat will run under are what this check runs against: they
            // decide which agent providers take part, and an agent with too little confidence makes
            // a data source unavailable.
            //
            availableDataSources = await dataSourceService.GetAllowedDataSources(provider, chosenOptions, requestedDataSources);
        }
        catch (Exception exception)
        {
            logger.LogError(exception, "The data sources an assistant chat launcher would start its chat with could not be checked.");
            return new(null, originChatTemplate is null
                ? TB("The data sources selected by the assistant chat launcher could not be checked. No chat was created.")
                : string.Format(TB("The data sources selected by the chat template '{0}' could not be checked. No chat was created."), originChatTemplate.GetSafeName()));
        }

        var availableSelectedIds = availableDataSources.Select(source => source.Id).ToHashSet(StringComparer.OrdinalIgnoreCase);
        var unavailableDataSources = requestedDataSources.Where(source => !availableSelectedIds.Contains(source.Id)).Select(source => source.Name).ToList();
        if (unavailableDataSources.Count > 0)
            return new(null, originChatTemplate is null
                ? string.Format(TB("The following data sources selected by the assistant chat launcher are currently unavailable or not permitted for the selected provider: {0}"), string.Join(", ", unavailableDataSources))
                : string.Format(TB("The following data sources selected by the chat template '{0}' are currently unavailable or not permitted for the selected provider: {1}"), originChatTemplate.GetSafeName(), string.Join(", ", unavailableDataSources)));

        return new(chosenOptions, string.Empty);
    }
}