using System.Text;

namespace AIStudio.Assistants.BeyondFactsLab;

/// <summary>
/// Puts together the system prompts of the BeyondFacts Lab.
/// </summary>
/// <remarks>
/// The same parts, forms, and materials always give the same prompt, byte by byte, on every system. The parts which
/// stay the same during a conversation come first, the core and the guide, then the material, which changes seldom,
/// and the details last, so that providers which cache the beginning of a prompt can do so. The texts this class adds
/// itself are German, like the prompts.
/// </remarks>
public static class BflPromptComposer
{
    /// <summary>
    /// The line break of the prompt, the same on every system.
    /// </summary>
    private const char LINE_BREAK = '\n';

    /// <summary>
    /// Puts together the system prompt of a step.
    /// </summary>
    /// <param name="parts">The texts of the prompt.</param>
    /// <param name="step">The step the chat belongs to.</param>
    /// <param name="forms">The forms of the preparation, by their steps; a step this version cannot open is missing.</param>
    /// <param name="materials">What the prompt carries of the material of the preparation, see BflMaterialBudget.</param>
    /// <param name="responseLanguage">The name of the language the model answers in, e.g., the language of the app.</param>
    /// <returns>The system prompt.</returns>
    /// <exception cref="FormatException">The core prompt has a placeholder without a value.</exception>
    public static string Compose(BflPromptParts parts, BflStep step, IReadOnlyDictionary<BflStep, BflStepFormData> forms, IReadOnlyList<BflMaterialExcerpt> materials, string responseLanguage) => BflPromptTemplate.Fill(parts.Core, new Dictionary<string, string>(StringComparer.Ordinal)
    {
        [BflPromptTemplate.RESPONSE_LANGUAGE] = responseLanguage,
        [BflPromptTemplate.ADDRESS_FORM] = parts.Address.Trim(),
        [BflPromptTemplate.KNOWLEDGE] = parts.Knowledge.Trim(),
        [BflPromptTemplate.STEP] = parts.Step.Trim(),
        [BflPromptTemplate.MATERIALS] = Materials(materials),
        [BflPromptTemplate.DETAILS] = Details(step, forms),
        [BflPromptTemplate.MISSING_DETAILS] = MissingDetails(step, forms)
    }).ReplaceLineEndings(LINE_BREAK.ToString());

    /// <summary>
    /// Puts together the system prompt of the conversation about whether the lab fits a task.
    /// </summary>
    /// <remarks>
    /// It knows no preparation and leaves out the guide, so that it stays short.
    /// </remarks>
    /// <param name="parts">The texts of the prompt.</param>
    /// <param name="responseLanguage">The name of the language the model answers in, e.g., the language of the app.</param>
    /// <returns>The system prompt.</returns>
    /// <exception cref="FormatException">The prompt has a placeholder without a value.</exception>
    public static string ComposeOnboarding(BflOnboardingPromptParts parts, string responseLanguage) => BflPromptTemplate.Fill(parts.Onboarding, new Dictionary<string, string>(StringComparer.Ordinal)
    {
        [BflPromptTemplate.RESPONSE_LANGUAGE] = responseLanguage,
        [BflPromptTemplate.ADDRESS_FORM] = parts.Address.Trim()
    }).ReplaceLineEndings(LINE_BREAK.ToString());

    /// <summary>
    /// Lists the material of the preparation, each with its name and as much of its text as fits, or for an image,
    /// whether it goes along.
    /// </summary>
    /// <remarks>
    /// The model learns which material is shortened, so that it neither takes the beginning for the whole nor
    /// guesses what follows, and which text is the transcript of a recording, whose spelling may be off.
    /// </remarks>
    /// <param name="materials">What the prompt carries of each material, in the order the person added them.</param>
    private static string Materials(IReadOnlyList<BflMaterialExcerpt> materials)
    {
        if (materials.Count is 0)
            return "Die Person hat kein Material hinzugefügt.";

        var text = new StringBuilder();
        for (var index = 0; index < materials.Count; index++)
        {
            var excerpt = materials[index];
            var material = excerpt.Share.Material;
            if (index > 0)
                text.Append(LINE_BREAK);

            text.Append($"## Material {index + 1}: „{material.Name}“").Append(LINE_BREAK);
            if (material.Kind is BflMaterialKind.IMAGE)
            {
                text.Append(excerpt.Share.Image switch
                {
                    BflImageDelivery.SENT => "(Ein Bild. Es liegt der ersten Nachricht dieses Gesprächs bei.)",
                    BflImageDelivery.OVER_THE_LIMIT => "(Ein Bild. Das Modell nimmt nicht so viele Bilder auf einmal an. Du kennst nur seinen Namen.)",
                    _ => "(Ein Bild. Das Modell kann keine Bilder sehen. Du kennst nur seinen Namen.)",
                }).Append(LINE_BREAK);
                continue;
            }

            if (material.Kind is BflMaterialKind.RECORDING)
                text.Append("(Das Transkript einer Aufnahme. Namen und Fachbegriffe können falsch geschrieben sein.)").Append(LINE_BREAK);

            if (excerpt.Text.Length is 0)
            {
                text.Append("(Für dieses Material reicht der Platz im Kontext des Modells nicht. Du kennst nur seinen Namen.)").Append(LINE_BREAK);
                continue;
            }

            if (material.IsShortened)
                text.Append("(Das Lab hat nur den Anfang dieses Materials übernommen. Den Rest kennst du nicht.)").Append(LINE_BREAK);

            if (!excerpt.Share.IsComplete)
                text.Append($"(Gekürzt: Hier steht nur der Anfang, etwa {excerpt.Share.Percent} % des Materials. Für mehr reicht der Platz im Kontext des Modells nicht.)").Append(LINE_BREAK);

            text.Append(LINE_BREAK).Append(excerpt.Text.Trim()).Append(LINE_BREAK);
        }

        return text.ToString().TrimEnd();
    }

    /// <summary>
    /// Lists what the person entered into the forms, step by step.
    /// </summary>
    /// <remarks>
    /// Something the person confided, such as their personal involvement, reaches only the chat of its own step:
    /// no other step may confront them with it by surprise.
    /// </remarks>
    /// <param name="step">The step the chat belongs to.</param>
    /// <param name="forms">The forms of the preparation, by their steps.</param>
    private static string Details(BflStep step, IReadOnlyDictionary<BflStep, BflStepFormData> forms)
    {
        var text = new StringBuilder();
        foreach (var candidate in BflStep.All)
        {
            if (!forms.TryGetValue(candidate, out var form))
                continue;

            var lines = new List<string>();
            foreach (var field in BflFieldCatalog.ForStep(candidate))
            {
                if (field.IsPersonalDisclosure && candidate != step)
                    continue;

                var value = ValueOf(field, form);
                if (value.Length is 0)
                    continue;

                var marker = field.IsPersonalDisclosure ? " (persönliche Angabe)" : string.Empty;
                lines.Add($"- {field.Label}{marker}: {value.Replace("\n", "\n  ", StringComparison.Ordinal)}");
            }

            if (lines.Count is 0)
                continue;

            if (text.Length > 0)
                text.Append(LINE_BREAK);

            text.Append("## ").Append(StepHeading(candidate, step)).Append(LINE_BREAK);
            foreach (var line in lines)
                text.Append(line).Append(LINE_BREAK);
        }

        return text.Length is 0 ? "Die Person hat noch keine Angaben gemacht." : text.ToString().TrimEnd();
    }

    /// <summary>
    /// Lists the key details the forms still lack, step by step.
    /// </summary>
    /// <param name="step">The step the chat belongs to.</param>
    /// <param name="forms">The forms of the preparation, by their steps; a missing form counts as empty.</param>
    private static string MissingDetails(BflStep step, IReadOnlyDictionary<BflStep, BflStepFormData> forms)
    {
        var lines = new List<string>();
        foreach (var candidate in BflStep.All)
        {
            var missing = BflMissingDetails.Of(candidate, forms.GetValueOrDefault(candidate) ?? new BflStepFormData());
            if (missing.Count > 0)
                lines.Add($"- {StepHeading(candidate, step)}: {string.Join("; ", missing.Select(field => field.Label))}");
        }

        return lines.Count is 0 ? "Es fehlen keine wichtigen Angaben." : $"Diese wichtigen Angaben fehlen noch:{LINE_BREAK}{string.Join(LINE_BREAK, lines)}";
    }

    /// <summary>
    /// Gets the value of a field as the model reads it: the labels of chosen options, or the text with its lines.
    /// </summary>
    /// <param name="field">The field.</param>
    /// <param name="form">The form which holds the value.</param>
    /// <returns>The value, empty when the field has none.</returns>
    private static string ValueOf(BflFieldDefinition field, BflStepFormData form)
    {
        if (field.Kind is BflFieldKind.CHOICE or BflFieldKind.MULTI_CHOICE)
        {
            // An option this version does not know, e.g., one a newer version added, has no label to show:
            var chosen = form.GetChoices(field.Id);
            return string.Join(", ", field.Options.Where(option => chosen.Contains(option.Id)).Select(option => option.Label));
        }

        return form.Get(field.Id).Trim().ReplaceLineEndings(LINE_BREAK.ToString());
    }

    /// <summary>
    /// Gets the heading of a step in the details, which marks the step the chat belongs to.
    /// </summary>
    /// <param name="candidate">The step to name.</param>
    /// <param name="step">The step the chat belongs to.</param>
    private static string StepHeading(BflStep candidate, BflStep step) => candidate == step ? $"{candidate.Title} (dieser Schritt)" : candidate.Title;
}