temp-postgres 0.1.0

use std::ffi::{OsStr, OsString};
use std::path::{Path, PathBuf};
use std::time::Duration;

use crate::error::ErrorInner;
use crate::util::{KillOnDrop, TempDir};
use crate::Error;
use std::process::Command;

/// A temporary postgres instance.
///
/// All state of the postgres instance is stored in a temporary directory.
/// Unless disabled, the temporary directory is deleted when this object is dropped.
pub struct TempPostgres {
	tempdir: TempDir,
	server: KillOnDrop,
	log_path: PathBuf,
}

impl std::fmt::Debug for TempPostgres {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
		f.debug_struct("TempPostgres")
			.field("tempdir", &self.tempdir.path())
			.field("server_pid", &self.server.id())
			.finish_non_exhaustive()
	}
}

impl TempPostgres {
	/// Spawn a new postgres instance with a temporary state directory.
	pub async fn new() -> Result<Self, Error> {
		Self::from_builder(&TempPostgresBuilder::new()).await
	}

	/// Create a builder to customize your [`TempPostgres`].
	///
	/// After configuring the desirec options, run [`TempPostgresBuilder::spawn()`].
	pub fn builder() -> TempPostgresBuilder {
		TempPostgresBuilder::new()
	}

	/// Get the PID of the postgres server process.
	pub fn process_id(&self) -> u32 {
		self.server.id()
	}

	/// Get the path of the temporary state directory.
	pub fn directory(&self) -> &Path {
		self.tempdir.path()
	}

	/// Get the path of the log file.
	pub fn log_path(&self) -> &Path {
		&self.log_path
	}

	/// Read the contents of the log file.
	pub async fn read_log(&self) -> Result<String, Error> {
		use tokio::io::AsyncReadExt;

		let mut file = tokio::fs::File::open(&self.log_path)
			.await
			.map_err(|e| ErrorInner::Open(self.log_path.clone(), e))?;

		let mut buffer = String::new();
		file.read_to_string(&mut buffer)
			.await
			.map_err(|e| ErrorInner::Read(self.log_path.clone(), e))?;
		Ok(buffer)
	}

	/// Connect an asycnchronous client to the postgres instance.
	pub async fn client(&self) -> Result<tokio_postgres::Client, tokio_postgres::Error> {
		let (client, connection) = tokio_postgres::Config::new()
			.dbname("postgres")
			.host_path(self.directory())
			.connect_timeout(Duration::from_millis(10))
			.connect(tokio_postgres::NoTls)
			.await?;

		let directory  = self.directory().to_owned();
		tokio::spawn(async move {
			if let Err(e) = connection.await {
				panic!("Error in connection with postgres on {}: {e}", directory.display());
			}
		});

		Ok(client)
	}

	/// Enable or disable clean-up of the temporary directory when this object is dropped.
	pub fn set_clean_on_drop(&mut self, clean_on_drop: bool) {
		self.tempdir.set_clean_on_drop(clean_on_drop);
	}

	/// Kill the server and remove the temporary state directory on the filesystem.
	///
	/// Note that the server will also be killed when this object is dropped,
	/// and unless disabled, the temporary state directory will be removed by the [`Drop`] implementation too.
	///
	/// This function ignores the value of `clean_on_drop`.
	/// It also allows for better error handling compared to just dropping the object.
	pub async fn kill_and_clean(mut self) -> Result<(), Error> {
		self.server.kill()
			.map_err(ErrorInner::KillServer)?;

		let path = self.tempdir.path().to_owned();
		self.tempdir.close()
			.map_err(|e| ErrorInner::CleanDir(path, e))?;
		Ok(())
	}

	/// Kill the server, but leave the temporary state directory on the filesystem.
	///
	/// Note that the server will also be killed when this object is dropped.
	///
	/// This function ignores the value of `clean_on_drop`.
	/// It also allows for better error handling compared to just dropping the object.
	pub async fn kill_no_clean(mut self) -> Result<(), Error> {
		let _path = self.tempdir.into_path();
		self.server.kill()
			.map_err(ErrorInner::KillServer)?;
		Ok(())
	}

	/// Create the temporary directory and spawn a server based on the configuration of the given builder object.
	async fn from_builder(builder: &TempPostgresBuilder) -> Result<Self, Error> {
		let tempdir = builder.make_temp_dir().map_err(ErrorInner::MakeTempDir)?;

		let data_dir = tempdir.path().join("data");
		let pid_file = data_dir.join("postmaster.pid");
		let log_path = tempdir.path().join("output.log");

		let stderr = std::fs::File::create(&log_path)
			.map_err(|e| ErrorInner::Create(log_path.clone(), e))?;
		let stdout = stderr.try_clone()
			.map_err(|e| ErrorInner::Duplicate(log_path.clone(), e))?;

		crate::util::run_command(
			"pgctl initdb",
			tokio::process::Command::new(builder.get_pg_ctl_command())
				.env("TZ", builder.get_default_timezone())
				.arg("initdb")
				.arg("-D")
				.arg(&data_dir)
				.arg("-o")
				.arg("--locale")
				.arg("-o")
				.arg(builder.get_default_locale())
				.arg("-o")
				.arg("--encoding=UTF8")
				.arg("-o")
				.arg("--no-sync")
				.arg("-o")
				.arg("--no-instructions")
				.arg("-o")
				.arg("--auth=trust")
		).await?;

		let server = Command::new(builder.get_postgres_command())
			.stderr(stderr)
			.stdout(stdout)
			.arg("-D")
			.arg(&data_dir)
			.arg("-k")
			.arg(tempdir.path())
			.arg("-c")
			.arg("listen_addresses=")
			.arg("-F")
			.spawn()
			.map_err(|e| ErrorInner::SpawnServer(builder.get_postgres_command_string(), e))?;
		let server = KillOnDrop::new(server);

		wait_ready(&pid_file, Duration::from_millis(500)).await?;

		Ok(Self {
			tempdir,
			server,
			log_path,
		})
	}
}

/// Wait for the postgres server to be ready.
async fn wait_ready(pid_file: &Path, timeout: Duration) -> Result<(), Error> {
	let deadline = std::time::Instant::now() + timeout;
	loop {
		if poll_ready(pid_file).await? {
			return Ok(())
		} else if std::time::Instant::now() > deadline {
			return Err(ErrorInner::ServerReadyTimeout.into());
		} else {
			tokio::time::sleep(Duration::from_millis(10)).await;
		}
	}
}

/// Check if the postgres server is ready by reading the PID file.
async fn poll_ready(pid_file: &Path) -> Result<bool, Error> {
	use tokio::io::AsyncReadExt;
	let mut file = match tokio::fs::File::open(&pid_file).await {
		Ok(x) => x,
		Err(e) => {
			if e.kind() == std::io::ErrorKind::NotFound {
				return Ok(false);
			} else {
				return Err(ErrorInner::Open(pid_file.to_owned(), e).into());
			}
		}
	};

	let mut data = Vec::new();
	file.read_to_end(&mut data)
		.await
		.map_err(|e| ErrorInner::Read(pid_file.to_owned(), e))?;

	// Strip trailing whitespace.
	while data.last().is_some_and(|&b| b == b'\n' || b == b'\r' || b == b' ') {
		data.pop();
	};
	Ok(data.ends_with(b"\nready"))
}

/// Builder for customizing your [`TempPostgres`] object.
///
/// After configuring the desired options, run [`TempPostgresBuilder::spawn()`].
#[derive(Debug)]
pub struct TempPostgresBuilder {
	/// The parent directory for the temporary directory.
	///
	/// Use the system default if set to `None`.
	parent_directory: Option<PathBuf>,

	/// The default locale for the database.
	default_locale: Option<OsString>,

	/// The default timezone for the database.
	default_timezone: Option<OsString>,

	/// The postgres command to execute.
	postgres_command: Option<OsString>,

	/// The pg_ctl command to execute.
	pg_ctl_command: Option<OsString>,

	/// Clean up the temprorary directory when the [`TempPostgres`] object is dropped.
	clean_on_drop: bool,
}

impl TempPostgresBuilder {
	/// Create a new builder.
	pub fn new() -> Self {
		Self {
			parent_directory: None,
			default_locale: None,
			default_timezone: None,
			postgres_command: None,
			pg_ctl_command: None,
			clean_on_drop: true,
		}
	}

	/// Spawn the postgres server and connect to it.
	pub async fn spawn(&self) -> Result<TempPostgres, Error> {
		TempPostgres::from_builder(self).await
	}

	/// Enable or disable cleaning of the temporary state directory when the [`TempPostgres`] object is dropped.
	///
	/// This can also be changed after creation with [`TempPostgres::set_clean_on_drop()`].
	pub fn clean_on_drop(mut self, clean_on_drop: bool) -> Self {
		self.clean_on_drop = clean_on_drop;
		self
	}

	/// Set the default locale for the database.
	///
	/// This is passed to the `pg_ctl` command when initializing the database.
	///
	/// Defaults to "C" if not specified.
	pub fn default_locale(mut self, locale: impl Into<OsString>) -> Self {
		self.default_locale = Some(locale.into());
		self
	}

	/// Set the default timezone for the database.
	///
	/// This is passed to the `pg_ctl` command when initializing the database.
	///
	/// Defaults to "UTC" if not specified.
	pub fn default_timezone(mut self, timezone: impl Into<OsString>) -> Self {
		self.default_timezone = Some(timezone.into());
		self
	}

	/// Overwrite the `postgres` command to run.
	///
	/// Can be used to run a `postgres` binary from an alternative location.
	pub fn postgres_command(mut self, command: impl Into<OsString>) -> Self {
		self.postgres_command = Some(command.into());
		self
	}

	/// Overwrite the `pg_ctl` command to run.
	///
	/// Can be used to run a `pg_ctl` binary from an alternative location.
	pub fn pg_ctl_command(mut self, command: impl Into<OsString>) -> Self {
		self.pg_ctl_command = Some(command.into());
		self
	}

	/// Get the default locale for the database.
	fn get_default_locale(&self) -> &OsStr {
		self.default_locale
			.as_deref()
			.unwrap_or("C".as_ref())
	}

	/// Get the default timezone for the database.
	fn get_default_timezone(&self) -> &OsStr {
		self.default_locale
			.as_deref()
			.unwrap_or("UTC".as_ref())
	}

	/// Get the postgres command to execute to run postgres.
	fn get_postgres_command(&self) -> &OsStr {
		self.postgres_command
			.as_deref()
			.unwrap_or("postgres".as_ref())
	}

	/// Get the postgres command to execute to run postgres as a string, for diagnostic purposes.
	fn get_postgres_command_string(&self) -> String {
		self.get_postgres_command().to_string_lossy().into()
	}

	/// Get the postgres command to execute to run postgres.
	fn get_pg_ctl_command(&self) -> &OsStr {
		self.pg_ctl_command
			.as_deref()
			.unwrap_or("pg_ctl".as_ref())
	}

	/// Create a temporary directory according to the configuration of the builder.
	fn make_temp_dir(&self) -> std::io::Result<TempDir> {
		match &self.parent_directory {
			Some(dir) => TempDir::new_in(dir, self.clean_on_drop),
			None => TempDir::new(self.clean_on_drop),
		}
	}
}

impl Default for TempPostgresBuilder {
	fn default() -> Self {
		Self::new()
	}
}