using System;
using System.Collections.Generic;
using System.IO;
using System.Text;

namespace ln.templates.html
{
    public class FileSystemTemplateSource : ITemplateSource
    {
        public String BasePath { get; }

        Dictionary<string, TemplateDocument> templateDocuments = new Dictionary<string, TemplateDocument>();

        public FileSystemTemplateSource(String path)
        {
            if (!Directory.Exists(path))
                throw new FileNotFoundException();
            BasePath = path;
        }

        public TemplateDocument GetTemplateByPath(string path)
        {
            string templatePath = Path.Combine(BasePath, path);
            if (!File.Exists(templatePath))
            {
                if (templateDocuments.ContainsKey(path))
                    templateDocuments.Remove(path);

                throw new FileNotFoundException();
            }

            if (!templateDocuments.TryGetValue(path,out TemplateDocument templateDocument))
            {
                templateDocument = ReadTemplateDocument(path);
                templateDocuments[path] = templateDocument;
            } else
            {
                DateTime templateDateTime = File.GetLastWriteTime(templatePath);
                if (templateDateTime.Ticks != templateDocument.TemplateVersion)
                {
                    templateDocument = ReadTemplateDocument(path);
                    templateDocuments[path] = templateDocument;
                }
            }

            return templateDocument;
        }

        TemplateDocument ReadTemplateDocument(string path)
        {
            string templatePath = Path.Combine(BasePath, path);

            TemplateReader templateReader = new TemplateReader();
            using (StreamReader sr = new StreamReader(templatePath))
            {
                templateReader.Read(sr);
            }
            templateReader.TemplateDocument.TemplateVersion = File.GetLastWriteTime(templatePath).Ticks;

            return templateReader.TemplateDocument;
        }
    }
}