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//! Create and manage temporary file used for unit tests.
//! File is deleted on Drop

/**
 * File content initializer closure.
 * Initializes TestFile with content.
*/
/*
#![feature(trait_alias)]
pub trait FileInitializer = Fn (&mut TestFile) -> std::io::Result<()>;
*/

use std::mem::ManuallyDrop;

/**
 * TestFile structure.
 * Holds opened File and PathBuf.
 * Files are created in temporary directory with unique names. Deleted on Drop.
 * This structure can be dereferenced to &File and implements
 * AsRef for Path, PathBuf and File.
*/
pub struct TestFile {
      file : ManuallyDrop<std::fs::File>,
      path : std::path::PathBuf
}

/**
  Removes TestFile from disk.
*/
impl Drop for TestFile {
    fn drop(&mut self) {
        unsafe { ManuallyDrop::drop(&mut self.file) };
        let _ = std::fs::remove_file(&self.path);
    }
}

use std::ops::{Deref,DerefMut};
use std::convert::{AsRef,AsMut};

impl AsRef<std::path::Path> for TestFile {
   fn as_ref(&self) -> &std::path::Path {
       &self.path
   }
}

impl AsRef<std::path::PathBuf> for TestFile {
    fn as_ref(&self) -> &std::path::PathBuf {
        &self.path
    }
}

impl AsRef<std::fs::File> for TestFile {
   fn as_ref(&self) -> &std::fs::File {
       &self.file
   }
}

impl AsMut<std::fs::File> for TestFile {
   fn as_mut(&mut self) -> &mut std::fs::File {
       &mut self.file
   }
}

impl AsMut<dyn std::io::Read> for TestFile {
   fn as_mut(&mut self) -> &mut (dyn std::io::Read + 'static) {
        self.file.deref_mut()
   }
}

impl AsMut<dyn std::io::Write> for TestFile {
   fn as_mut(&mut self) -> &mut (dyn std::io::Write + 'static) {
        self.file.deref_mut()
   }
}

impl AsMut<TestFile> for TestFile {
   fn as_mut(&mut self) -> &mut TestFile {
        self
   }
}

impl Deref for TestFile {
   type Target = std::fs::File;
   fn deref(&self) -> &Self::Target { &self.file }
}

impl DerefMut for TestFile {
   fn deref_mut(&mut self) -> &mut Self::Target { &mut self.file }
}

/**
 * Turns file into TestFile
*/
pub fn from_file(path: impl AsRef<std::path::Path>) -> TestFile {
   std::fs::OpenOptions::new().read(true).write(true).create_new(false).open(path.as_ref()).map(
      |f| TestFile{ file:ManuallyDrop::new(f), path:std::path::PathBuf::new() }).map(
      |mut tf| { tf.path.push(path.as_ref());tf})
      .unwrap()
}

/**
 * Create an empty test file
*/
pub fn empty() -> TestFile {
    create(|_unused| Ok(()))
}

/**
  Create a TestFile from string
*/
pub fn from<T: AsRef<str>>(content: T) -> TestFile {
    use std::io::Write;
    create(|tfile| tfile.file.write_all(content.as_ref().as_bytes()))
}

/**
 * Create test file with content supplied by initializer closure
*/
pub fn create<I>(initializer: I) -> TestFile
     where I: Fn (&mut TestFile) -> std::io::Result<()> {
   let mut retries = 6;
   let mut rng = rand::thread_rng();
   use rand::Rng;
   use std::fs::OpenOptions;
   use std::io::{Seek, SeekFrom};

   while retries > 0 {
      retries-=1;
      let mut tmp = std::env::temp_dir();
      tmp.push(format!("TMP{}",rng.gen_range::<_,u32,u32>(0,1000)));
      match OpenOptions::new().read(true).write(true).create_new(true).open(&tmp).map(
      |f| TestFile{ file:ManuallyDrop::new(f), path:tmp }
      ).and_then(|mut tfile:TestFile| -> std::io::Result<TestFile> { match initializer(<TestFile as AsMut<TestFile>>::as_mut(&mut tfile)) { Ok(_) => Ok(tfile), Err(ioerr) => Err(ioerr) }}
      ).and_then(|mut tfile| match tfile.file.seek(SeekFrom::Start(0)) { Ok(_) => Ok(tfile), Err(ioerr) => Err(ioerr) }
      ).and_then(|mut tfile| match <dyn std::io::Write>::flush(<TestFile as AsMut<std::fs::File>>::as_mut(&mut tfile)) { Ok(_) => Ok(tfile), Err(ioerr) => Err(ioerr) }
      ) {
         Ok(tfile) => return tfile,
         Err(_) => continue
      }
   }
   panic!("Can't create temporary file")
}

/**
 * Generate unique tmp file name
 */
pub fn generate_name() -> std::path::PathBuf {
   let mut retries = 10;
   let mut rng = rand::thread_rng();
   use rand::Rng;
   use std::fs::OpenOptions;

   while retries > 0 {
      retries-=1;
      let mut tmp = std::env::temp_dir();
      tmp.push(format!("TMP{}", rng.gen_range::<_,u32,u32>(0,1000)));
      match OpenOptions::new().read(true).write(true).create_new(true).open(&tmp).map(
      |f| { drop(f); let _ignored = std::fs::remove_file(&tmp); () })
      {
         Ok(()) => return tmp,
         Err(_) => continue
      }
   }
   panic!("Can't generate suitable tmp file name");
}

#[cfg(test)]
#[path= "./lib_tests.rs"]
mod tests;