// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Xml.Linq;
using static XliffTasks.Model.XlfNames;

namespace XliffTasks.Model;

internal static class XElementExtensions
{
    /// <summary>
    /// Returns the effective target value of a <code>trans-unit</code> element in an XLIFF file.
    /// If the <code>trans-unit</code> has no <code>target</code> child, returns the value of the <code>source</code>
    /// child.
    /// </summary>
    /// <param name="transUnitElement">An <see cref="XElement"/> representing the <code>trans-unit</code>.</param>
    /// <returns>The value of the <code>target</code> element if it exists; otherwise the value of the
    /// <code>source</code> element.</returns>
    public static string GetTargetValue(this XElement transUnitElement) => 
        transUnitElement.Element(Target)?.Value
        ?? transUnitElement.Element(Source).Value;

    /// <summary>
    /// Sets the target value of a <code>trans-unit</code> element in an XLIFF file.
    /// Creates the <code>target</code> element and <code>state</code> attribute as necessary.
    /// </summary>
    /// <param name="transUnitElement">An <see cref="XElement"/> representing the <code>trans-unit</code>.</param>
    /// <param name="value">The new target value.</param>
    public static void SetTargetValue(this XElement transUnitElement, string value)
    {
        XElement targetElement = transUnitElement.Element(Target);
        if (targetElement == null)
        {
            XElement sourceElement = transUnitElement.Element(Source);
            targetElement = new XElement(Target, new XAttribute("state", "new"));
            sourceElement.AddAfterSelf(targetElement);
        }

        targetElement.Value = value;
        if (targetElement.Attribute("state") == null)
        {
            targetElement.Add(new XAttribute("state", "new"));
        }
    }

    /// <summary>
    /// Returns the effective target translation of a <code>trans-unit</code> element in an XLIFF file.
    /// If the <code>trans-unit</code> has no <code>target</code> element or <code>state</code> attribute,
    /// returns a default value ("new").
    /// </summary>
    /// <param name="transUnitElement">An <see cref="XElement"/> representing the <code>trans-unit</code>.</param>
    /// <returns>The value of the <code>state</code> attribute if it exists, otherwise "new".</returns>
    public static string GetTargetState(this XElement transUnitElement) =>
        transUnitElement.Element(Target)?.Attribute("state")?.Value
        ?? "new";

    /// <summary>
    /// Sets the target translation state of a <code>trans-unit</code> element in an XLIFF file.
    /// Creates the <code>target</code> element and <code>state</code> attribute as necessary.
    /// </summary>
    /// <param name="transUnitElement">An <see cref="XElement"/> representing the <code>trans-unit</code>.</param>
    /// <param name="value">The new state value.</param>
    public static void SetTargetState(this XElement transUnitElement, string value)
    {
        XElement targetElement = transUnitElement.Element(Target);
        if (targetElement == null)
        {
            XElement sourceElement = transUnitElement.Element(Source);
            targetElement = new XElement(Target);
            sourceElement.AddAfterSelf(targetElement);
        }

        XAttribute stateAttribute = targetElement.Attribute("state");
        if (stateAttribute == null)
        {
            stateAttribute = new XAttribute("state", value);
            targetElement.Add(stateAttribute);
        }
        else
        {
            stateAttribute.Value = value;
        }
    }

    /// <summary>
    /// Gets the <code>source</code> value of a <code>trans-unit</code> element in an XLIFF file.
    /// </summary>
    /// <param name="transUnitElement">An <see cref="XElement"/> representing the <code>trans-unit</code>.</param>
    /// <returns>The value of the <code>source</code> element.</returns>
    public static string GetSourceValue(this XElement transUnitElement) =>
        transUnitElement.Element(Source).Value;

    /// <summary>
    /// Sets the <code>source</code> value of a <code>trans-unit</code> element in an XLIFF file.
    /// </summary>
    /// <param name="transUnitElement">An <see cref="XElement"/> representing the <code>trans-unit</code>.</param>
    /// <param name="value">The new <code>source</code> value.</param>
    public static void SetSourceValue(this XElement transUnitElement, string value) =>
        transUnitElement.Element(Source).Value = value;

    /// <summary>
    /// Gets the <code>note</code> value of a <code>trans-unit</code> element in an XLIFF file.
    /// </summary>
    /// <param name="transUnitElement">An <see cref="XElement"/> representing the <code>trans-unit</code>.</param>
    /// <returns>The value of the <code>note</code> element, or <code>null</code> if it does not exist.</returns>
    public static string GetNoteValue(this XElement transUnitElement) =>
        transUnitElement.Element(Note)?.Value;

    /// <summary>
    /// Sets the <code>note</code> value of a <code>trans-unit</code> element in an XLIFF file.
    /// Creates the <code>note</code> element as needed, and places it in the correct location
    /// relative to the <code>source</code> and <code>target</code> elements.
    /// </summary>
    /// <param name="transUnitElement">An <see cref="XElement"/> representing the <code>trans-unit</code>.</param>
    /// <param name="value">The new <code>note</code> value.</param>
    public static void SetNoteValue(this XElement transUnitElement, string value)
    {
        XElement noteElement = transUnitElement.Element(Note);
        if (noteElement == null)
        {
            XElement priorElement = transUnitElement.Element(Target) ?? transUnitElement.Element(Source);
            noteElement = new XElement(Note);
            priorElement.AddAfterSelf(noteElement);
        }

        noteElement.Value = value;
        noteElement.SelfCloseIfPossible();
    }

    /// <summary>
    /// Gets the <code>id</code> value of a <code>trans-unit</code> element in an XLIFF file.
    /// </summary>
    /// <param name="transUnitElement">An <see cref="XElement"/> representing the <code>trans-unit</code>.</param>
    /// <returns>The value of the <code>id</code> attribute.</returns>
    public static string GetId(this XElement transUnitElement) =>
        transUnitElement.Attribute("id").Value;
}