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| -rw-r--r-- | pkgs/by-name/mp/mpdpopm/src/messages.rs | 409 |
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diff --git a/pkgs/by-name/mp/mpdpopm/src/messages.rs b/pkgs/by-name/mp/mpdpopm/src/messages.rs new file mode 100644 index 00000000..171a246a --- /dev/null +++ b/pkgs/by-name/mp/mpdpopm/src/messages.rs @@ -0,0 +1,409 @@ +// Copyright (C) 2020-2025 Michael herstine <sp1ff@pobox.com> +// +// This file is part of mpdpopm. +// +// mpdpopm is free software: you can redistribute it and/or modify it under the terms of the GNU +// General Public License as published by the Free Software Foundation, either version 3 of the +// License, or (at your option) any later version. +// +// mpdpopm is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even +// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General +// Public License for more details. +// +// You should have received a copy of the GNU General Public License along with mpdpopm. If not, +// see <http://www.gnu.org/licenses/>. + +//! # messages +//! +//! Process incoming messages to the [mpdpopm](https://github.com/sp1ff/mpdpopm) daemon. +//! +//! # Introduction +//! +//! The [mpdpopm](https://github.com/sp1ff/mpdpopm) daemon accepts commands over a dedicated +//! [channel](https://www.musicpd.org/doc/html/protocol.html#client-to-client). It also provides for +//! a generalized framework in which the [mpdpopm](https://github.com/sp1ff/mpdpopm) administrator +//! can define new commands backed by arbitrary command execution server-side. +//! +//! # Commands +//! +//! The following commands are built-in: +//! +//! - set rating: `rate RATING( TRACK)?` +//! - set playcount: `setpc PC( TRACK)?` +//! - set lastplayed: `setlp TIMESTAMP( TRACK)?` +//! +//! There is no need to provide corresponding accessors since this functionality is already provided +//! via "sticker get". Dedicated accessors could provide the same functionality with slightly more +//! convenience since the sticker name would not have to be specified (as with "sticker get") & may +//! be added at a later date. +//! +//! I'm expanding the MPD filter functionality to include attributes tracked by mpdpopm: +//! +//! - findadd replacement: `findadd FILTER [sort TYPE] [window START:END]` +//! (cf. [here](https://www.musicpd.org/doc/html/protocol.html#the-music-database)) +//! +//! - searchadd replacement: `searchadd FILTER [sort TYPE] [window START:END]` +//! (cf. [here](https://www.musicpd.org/doc/html/protocol.html#the-music-database)) +//! +//! Additional commands may be added through the +//! [generalized commands](crate::commands#the-generalized-command-framework) feature. + +use crate::{ + clients::{Client, IdleClient, PlayerStatus}, + filters::ExpressionParser, + filters_ast::{FilterStickerNames, evaluate}, +}; + +use anyhow::{Context, Error, Result, anyhow, bail}; +use boolinator::Boolinator; +use tracing::debug; + +use std::collections::VecDeque; + +/// Break `buf` up into individual tokens while removing MPD-style quoting. +/// +/// When a client sends a command to [mpdpopm](crate), it will look like this on the wire: +/// +/// ```text +/// sendmessage ${CHANNEL} "some-command \"with space\" simple \"'with single' and \\\\\"" +/// ``` +/// +/// In other words, the MPD "sendmessage" command takes two parameters: the channel and the +/// message. The recipient (i.e. us) is responsible for breaking up the message into its constituent +/// parts (a command name & its arguments in our case). +/// +/// The message will perforce be quoted according ot the MPD rules: +/// +/// 1. an un-quoted token may contain any printable ASCII character except space, tab, ' & " +/// +/// 2. to include spaces, tabs, '-s or "-s, the token must be enclosed in "-s, and any "-s or \\-s +/// therein must be backslash escaped +/// +/// When the messages is delivered to us, it has already been un-escaped; i.e. we will see the +/// string: +/// +/// ```text +/// some-command "with space" simple "'with single' and \\" +/// ``` +/// +/// This function will break that string up into individual tokens with one more level +/// of escaping removed; i.e. it will return an iterator that will yield the four tokens: +/// +/// 1. some-command +/// 2. with space +/// 3. simple +/// 4. 'with single' and \\ +/// +/// [MPD](https://github.com/MusicPlayerDaemon/MPD) has a nice +/// [implementation](https://github.com/MusicPlayerDaemon/MPD/blob/master/src/util/Tokenizer.cxx#L170) +/// that modifies the string in place by copying subsequent characters on top of escape characters +/// in the same buffer, inserting nulls in between the resulting tokens,and then working in terms of +/// pointers to the resulting null-terminated strings. +/// +/// Once I realized that I could split slices I saw how to implement an Iterator that do the same +/// thing (an idiomatic interface to the tokenization backed by a zero-copy implementation). I was +/// inspired by [My Favorite Rust Function +/// Signature](<https://www.brandonsmith.ninja/blog/favorite-rust-function>). +/// +/// NB. This method works in terms of a slice of [`u8`] because we can't index into Strings in +/// Rust, and MPD deals only in terms of ASCII at any rate. +pub fn tokenize(buf: &mut [u8]) -> impl Iterator<Item = Result<&[u8]>> { + TokenIterator::new(buf) +} + +struct TokenIterator<'a> { + /// The slice on which we operate; modified in-place as we yield tokens + slice: &'a mut [u8], + /// Index into [`slice`] of the first non-whitespace character + input: usize, +} + +impl<'a> TokenIterator<'a> { + pub fn new(slice: &'a mut [u8]) -> TokenIterator<'a> { + let input = match slice.iter().position(|&x| x > 0x20) { + Some(n) => n, + None => slice.len(), + }; + TokenIterator { slice, input } + } +} + +impl<'a> Iterator for TokenIterator<'a> { + type Item = Result<&'a [u8]>; + + fn next(&mut self) -> Option<Self::Item> { + let nslice = self.slice.len(); + if self.slice.is_empty() || self.input == nslice { + None + } else if '"' == self.slice[self.input] as char { + // This is NextString in MPD: walk self.slice, un-escaping characters, until we find + // a closing ". Note that we un-escape by moving characters forward in the slice. + let mut inp = self.input + 1; + let mut out = self.input; + while self.slice[inp] as char != '"' { + if '\\' == self.slice[inp] as char { + inp += 1; + if inp == nslice { + return Some(Err(anyhow!("Trailing backslash"))); + } + } + self.slice[out] = self.slice[inp]; + out += 1; + inp += 1; + if inp == nslice { + return Some(Err(anyhow!("No closing quote"))); + } + } + // The next token is in self.slice[self.input..out] and self.slice[inp] is " + let tmp = std::mem::take(&mut self.slice); + let (_, tmp) = tmp.split_at_mut(self.input); + let (result, new_slice) = tmp.split_at_mut(out - self.input); + self.slice = new_slice; + // strip any leading whitespace + self.input = inp - out + 1; // +1 to skip the closing " + while self.input < self.slice.len() && self.slice[self.input] as char == ' ' { + self.input += 1; + } + Some(Ok(result)) + } else { + // This is NextUnquoted in MPD; walk self.slice, validating characters until the end + // or the next whitespace + let mut i = self.input; + while i < nslice { + if 0x20 >= self.slice[i] { + break; + } + if self.slice[i] as char == '"' || self.slice[i] as char == '\'' { + return Some(Err(anyhow!("Invalid char: `{}`", self.slice[i]))); + } + i += 1; + } + // The next token is in self.slice[self.input..i] & self.slice[i] is either one- + // past-the end or whitespace. + let tmp = std::mem::take(&mut self.slice); + let (_, tmp) = tmp.split_at_mut(self.input); + let (result, new_slice) = tmp.split_at_mut(i - self.input); + self.slice = new_slice; + // strip any leading whitespace + self.input = match self.slice.iter().position(|&x| x > 0x20) { + Some(n) => n, + None => self.slice.len(), + }; + Some(Ok(result)) + } + } +} + +/// Collective state needed for processing messages, both built-in & generalized +#[derive(Default)] +pub struct MessageProcessor {} + +impl MessageProcessor { + /// Whip up a new instance; other than cloning the iterators, should just hold references in the + /// enclosing scope + pub fn new() -> MessageProcessor { + Self::default() + } + + /// Read messages off the commands channel & dispatch 'em + pub async fn check_messages<'a>( + &self, + client: &mut Client, + idle_client: &mut IdleClient, + state: PlayerStatus, + command_chan: &str, + stickers: &FilterStickerNames<'a>, + ) -> Result<()> { + let m = idle_client + .get_messages() + .await + .context("Failed to `get_messages` from client")?; + + for (chan, msgs) in m { + // Only supporting a single channel, ATM + (chan == command_chan).ok_or_else(|| anyhow!("Unknown chanell: `{}`", chan))?; + for msg in msgs { + self.process(msg, client, &state, stickers).await?; + } + } + + Ok(()) + } + + /// Process a single command + pub async fn process<'a>( + &self, + msg: String, + client: &mut Client, + state: &PlayerStatus, + stickers: &FilterStickerNames<'a>, + ) -> Result<()> { + if let Some(stripped) = msg.strip_prefix("findadd ") { + self.findadd(stripped.to_string(), client, stickers, state) + .await + } else if let Some(stripped) = msg.strip_prefix("searchadd ") { + self.searchadd(stripped.to_string(), client, stickers, state) + .await + } else { + unreachable!("Unkonwn command") + } + } + + /// Handle `findadd': "FILTER [sort TYPE] [window START:END]" + async fn findadd<'a>( + &self, + msg: String, + client: &mut Client, + stickers: &FilterStickerNames<'a>, + _state: &PlayerStatus, + ) -> Result<()> { + let mut buf = msg.into_bytes(); + let args: VecDeque<&str> = tokenize(&mut buf) + .map(|r| match r { + Ok(buf) => Ok(std::str::from_utf8(buf) + .context("Failed to interpete `findadd` string as utf8")?), + Err(err) => Err(err), + }) + .collect::<Result<VecDeque<&str>>>()?; + + debug!("findadd arguments: {:#?}", args); + + // there should be 1, 3 or 5 arguments. `sort' & `window' are not supported, yet. + + // ExpressionParser's not terribly ergonomic: it returns a ParesError<L, T, E>; T is the + // offending token, which has the same lifetime as our input, which makes it tough to + // capture. Nor is there a convenient way in which to treat all variants other than the + // Error Trait. + let ast = match ExpressionParser::new().parse(args[0]) { + Ok(ast) => ast, + Err(err) => { + bail!("Failed to parse filter: `{}`", err) + } + }; + + debug!("ast: {:#?}", ast); + + let mut results = Vec::new(); + for song in evaluate(&ast, true, client, stickers) + .await + .context("Failed to evaluate filter")? + { + results.push(client.add(&song).await); + } + match results + .into_iter() + .collect::<std::result::Result<Vec<()>, Error>>() + { + Ok(_) => Ok(()), + Err(err) => Err(err), + } + } + + /// Handle `searchadd': "FILTER [sort TYPE] [window START:END]" + async fn searchadd<'a>( + &self, + msg: String, + client: &mut Client, + stickers: &FilterStickerNames<'a>, + _state: &PlayerStatus, + ) -> Result<()> { + // Tokenize the message + let mut buf = msg.into_bytes(); + let args: VecDeque<&str> = tokenize(&mut buf) + .map(|r| match r { + Ok(buf) => Ok(std::str::from_utf8(buf) + .context("Failed to interpete `searchadd` string as utf8")?), + Err(err) => Err(err), + }) + .collect::<Result<VecDeque<_>>>()?; + + debug!("searchadd arguments: {:#?}", args); + + // there should be 1, 3 or 5 arguments. `sort' & `window' are not supported, yet. + + // ExpressionParser's not terribly ergonomic: it returns a ParesError<L, T, E>; T is the + // offending token, which has the same lifetime as our input, which makes it tough to + // capture. Nor is there a convenient way in which to treat all variants other than the + // Error Trait. + let ast = match ExpressionParser::new().parse(args[0]) { + Ok(ast) => ast, + Err(err) => { + bail!("Failed to parse filter: `{err}`") + } + }; + + debug!("ast: {:#?}", ast); + + let mut results = Vec::new(); + for song in evaluate(&ast, false, client, stickers) + .await + .context("Failed to evaluate ast")? + { + results.push(client.add(&song).await); + } + match results + .into_iter() + .collect::<std::result::Result<Vec<()>, Error>>() + { + Ok(_) => Ok(()), + Err(err) => Err(err), + } + } +} + +#[cfg(test)] +mod tokenize_tests { + use super::Result; + use super::tokenize; + + #[test] + fn tokenize_smoke() { + let mut buf1 = String::from("some-command").into_bytes(); + let x1: Vec<&[u8]> = tokenize(&mut buf1).collect::<Result<Vec<&[u8]>>>().unwrap(); + assert_eq!(x1[0], b"some-command"); + + let mut buf2 = String::from("a b").into_bytes(); + let x2: Vec<&[u8]> = tokenize(&mut buf2).collect::<Result<Vec<&[u8]>>>().unwrap(); + assert_eq!(x2[0], b"a"); + assert_eq!(x2[1], b"b"); + + let mut buf3 = String::from("a \"b c\"").into_bytes(); + let x3: Vec<&[u8]> = tokenize(&mut buf3).collect::<Result<Vec<&[u8]>>>().unwrap(); + assert_eq!(x3[0], b"a"); + assert_eq!(x3[1], b"b c"); + + let mut buf4 = String::from("a \"b c\" d").into_bytes(); + let x4: Vec<&[u8]> = tokenize(&mut buf4).collect::<Result<Vec<&[u8]>>>().unwrap(); + assert_eq!(x4[0], b"a"); + assert_eq!(x4[1], b"b c"); + assert_eq!(x4[2], b"d"); + + let mut buf5 = String::from("simple-command \"with space\" \"with '\"").into_bytes(); + let x5: Vec<&[u8]> = tokenize(&mut buf5).collect::<Result<Vec<&[u8]>>>().unwrap(); + assert_eq!(x5[0], b"simple-command"); + assert_eq!(x5[1], b"with space"); + assert_eq!(x5[2], b"with '"); + + let mut buf6 = String::from("cmd \"with\\\\slash and space\"").into_bytes(); + let x6: Vec<&[u8]> = tokenize(&mut buf6).collect::<Result<Vec<&[u8]>>>().unwrap(); + assert_eq!(x6[0], b"cmd"); + assert_eq!(x6[1], b"with\\slash and space"); + + let mut buf7 = String::from(" cmd \"with\\\\slash and space\" ").into_bytes(); + let x7: Vec<&[u8]> = tokenize(&mut buf7).collect::<Result<Vec<&[u8]>>>().unwrap(); + assert_eq!(x7[0], b"cmd"); + assert_eq!(x7[1], b"with\\slash and space"); + } + + #[test] + fn tokenize_filter() { + let mut buf1 = String::from(r#""(artist =~ \"foo\\\\bar\\\"\")""#).into_bytes(); + let x1: Vec<&[u8]> = tokenize(&mut buf1).collect::<Result<Vec<&[u8]>>>().unwrap(); + assert_eq!(1, x1.len()); + eprintln!("x1[0] is ``{}''", std::str::from_utf8(x1[0]).unwrap()); + assert_eq!( + std::str::from_utf8(x1[0]).unwrap(), + r#"(artist =~ "foo\\bar\"")"# + ); + } +} |