import { Lock } from "@hibas123/utils";
import * as fs from "fs";
import * as path from "path";
import { Adapter, Message, Formatted } from "@hibas123/logging";

const MAX_FILE_SIZE = 500000000;

export class LoggingFiles implements Adapter {
   file: Files;
   constructor(private filename: string, private maxFileSize = MAX_FILE_SIZE) {}

   init() {
      if (!this.file) {
         this.file = Files.getFile(this.filename);
         this.file.init(this.maxFileSize);
      }
   }

   flush(sync: boolean) {
      this.file.flush(sync);
   }

   onMessage(message: Message) {
      let msg = Buffer.from(Formatted.strip(message.text) + "\n");
      this.file.write(msg);
   }

   close() {
      this.file.close();
      this.file = undefined;
   }
}

//TODO: Optimise write path

const Debounce = (callback: () => void, iv = 500, max = 100) => {
   let to: any;
   let curr = 0;

   return {
      trigger: () => {
         curr++;
         if (curr >= max) {
            if (to) {
               clearTimeout(to);
               to = undefined;
            }
            curr = 0;
            callback();
         } else if (!to) {
            to = setTimeout(() => {
               to = undefined;
               curr = 0;
               callback();
            }, iv);
         }
      },
   };
};

export class Files {
   private open = 0;

   private static files = new Map<string, Files>();
   static getFile(filename: string): Files {
      filename = path.resolve(filename);
      let file = this.files.get(filename);
      if (!file) {
         file = new Files(filename);
         this.files.set(filename, file);
      }
      file.open++;
      return file;
   }

   private maxFileSize = MAX_FILE_SIZE;
   private size: number = 0;
   private stream: fs.WriteStream = undefined;
   private lock = new Lock();
   private debounce = Debounce(this.checkQueue.bind(this));

   #initialized = false;

   public get initlialized() {
      return this.#initialized;
   }

   private constructor(private file: string) {}

   public async init(maxFileSize: number) {
      if (this.#initialized) return;
      let lock = await this.lock.getLock();
      this.maxFileSize == maxFileSize;
      await this.initializeFile();
      this.#initialized = true;
      lock.release();
      this.checkQueue();
   }

   private async initializeFile(new_file = false) {
      try {
         if (this.stream) {
            this.stream.close();
         }
         const folder = path.dirname(this.file);
         if (folder) {
            if (!(await fsExists(folder))) {
               await fsMkDir(folder).catch(() => {}); //Could happen, if two seperate instances want to create the same folder so ignoring
            }
         }

         let size = 0;
         if (await fsExists(this.file)) {
            let stats = await fsStat(this.file);
            if (new_file || stats.size >= this.maxFileSize) {
               if (await fsExists(this.file + ".old"))
                  await fsUnlink(this.file + ".old");
               await fsMove(this.file, this.file + ".old");
            } else {
               size = stats.size;
            }
         }

         this.stream = fs.createWriteStream(this.file, { flags: "a" });
         this.size = size;
      } catch (e) {
         console.log(e);
         //TODO: is this the right behavior?
         process.exit(1);
      }
   }

   private queue: Buffer[] = [];

   async checkQueue() {
      if (this.lock.locked) return;
      let lock = await this.lock.getLock();
      let msg: Buffer;
      while ((msg = this.queue.shift())) {
         await this.write_to_file(msg);
      }
      lock.release();
   }

   public async close() {
      await this.flush(false);
      this.open--;
      if (this.open <= 0) {
         this.stream.close();
         Files.files.delete(this.file);
      }
   }

   public flush(sync: boolean) {
      if (sync) {
         // if sync flush, the process most likely is in failstate, so checkQueue stopped its work.
         let msg: Buffer;
         while ((msg = this.queue.shift())) {
            this.stream.write(msg);
         }
      } else {
         return Promise.resolve().then(async () => {
            const lock = await this.lock.getLock();
            lock.release();
            await this.checkQueue();
         });
      }
   }

   private async write_to_file(data: Buffer) {
      try {
         if (
            data.byteLength < this.maxFileSize &&
            this.size + data.byteLength > this.maxFileSize
         ) {
            await this.initializeFile(true);
         }
         this.size += data.byteLength;
         this.stream.write(data);
      } catch (err) {
         // TODO: Better error handling!
         console.error(err);
         this.initializeFile(false);
         this.write_to_file(data);
      }
   }

   public write(data: Buffer) {
      this.queue.push(data);
      this.debounce.trigger();
   }

   public dispose() {}
}

function fsUnlink(path) {
   return new Promise<void>((resolve, reject) => {
      fs.unlink(path, (err) => {
         if (err) reject(err);
         else resolve();
      });
   });
}

function fsStat(path: string) {
   return new Promise<fs.Stats>((resolve, reject) => {
      fs.stat(path, (err, stats) => {
         if (err) reject(err);
         else resolve(stats);
      });
   });
}

function fsMove(oldPath: string, newPath: string) {
   return new Promise<void>((resolve, reject) => {
      let callback = (err?) => {
         if (err) reject(err);
         else resolve();
      };

      fs.rename(oldPath, newPath, function (err) {
         if (err) {
            if (err.code === "EXDEV") {
               copy();
            } else {
               callback(err);
            }
            return;
         }
         callback();
      });

      function copy() {
         fs.copyFile(oldPath, newPath, (err) => {
            if (err) callback(err);
            else fs.unlink(oldPath, callback);
         });
      }
   });
}

function fsExists(path: string) {
   return new Promise<boolean>((resolve, reject) => {
      fs.exists(path, resolve);
   });
}

function fsMkDir(path: string) {
   return new Promise<void>((resolve, reject) => {
      fs.mkdir(path, (err) => (err ? reject(err) : resolve()));
   });
}