using System;
using System.Collections.Generic;
using System.IO;
using Jint;
using Jint.Native;
using Jint.Native.Json;
using Jint.Native.Object;
using ln.templates.html;

namespace ln.templates;

public class Template
{
    public Template(string filename, ITemplateResolver resolver)
    :this(filename, resolver, null)
    {}
    
    private Template(string filename, ITemplateResolver resolver, string source)
    {
        FileName = filename;
        Resolver = resolver;

        if (source is null)
        {
            Load();
        }
        else
        {
            Document = TemplateReader.Parse(source);
        }
    }


    private void Load()
    {
        Document = TemplateReader.ReadTemplate(FileName);
        LastWriteTime = File.GetLastWriteTime(FileName);

        string metaFileName = Path.Combine(Path.GetDirectoryName(FileName), String.Format("{0}.json",Path.GetFileNameWithoutExtension(FileName)));
        if (File.Exists(metaFileName))
        {
            using (StreamReader sr = new StreamReader(metaFileName))
                _jsonMeta = sr.ReadToEnd();
        }
        else
        {
            _jsonMeta = "{}";
        }
    }

    public ITemplateResolver Resolver { get; set; }
    public string FileName { get; }
    public TemplateDocument Document { get; private set; }
    public DateTime LastWriteTime { get; private set; }

    public void Render(TextWriter target) => Render(target, Array.Empty<KeyValuePair<string, object>>());
    public void Render(TextWriter target, IEnumerable<KeyValuePair<string, object>> scriptObjects)
    {
        Context context = new Context(Resolver, scriptObjects, target);
        Render(context);
    }

    public void Render(Context context) => Render(context, null);
    public void Render(Context context, ObjectInstance globals)
    {
        DateTime currentLastWriteTime = File.GetLastWriteTime(FileName);
        if (currentLastWriteTime > LastWriteTime)
            Load();


        if (_jsonMeta is not null)
            context.AssignGlobals(new JsonParser(context.Engine).Parse(_jsonMeta) as ObjectInstance);
        if (globals is not null)
            context.AssignGlobals(globals);
        
        Document.RenderTemplate(context);
        context.TargetWriter.Flush();
    }
    
    /* JSON Metadata */
    private string _jsonMeta;
    public JsValue GetMetaObject(Engine engine) => new JsonParser(engine).Parse(_jsonMeta);

}