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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. //! # Command Parser //! //! The command parser deals with interpreting textual input (like a //! command line) and executing a command with the provided parameters. //! //! Each command has a name which is typically a series of words. Some //! examples might be: //! //! * `show directory /bin` //! * `show struct` //! * `thread step in` //! * `thread step out` //! * `show process list` //! //! Don't worry about commands being long. Ideally, it will be rare that //! that the entire command would be typed by applying intelligent and //! interactive autocompletion. //! //! Commands can take parameters. Parameters can be marked as `required` //! or `repeatable`. Repeatable parameters generate a list of values //! rather than a single value. //! //! There are [three kinds of parameters]: //! //! * Simple: Just a value that is present in the command line. For //! example: `show interface eth0` where `eth0` is a simple //! parameter `name` which will have the value `eth0`. //! * Named: A name that precedes the value in the command line. For //! example: `show route src <ip> dst <ip>` where `src <ip>` and //! `dst <ip>` are both named parameters to a command `show route`. //! * Flag: Signify a `true` value when present. For example: //! `show log verbose` where `verbose` is a flag parameter that //! results in value of `true` when present and `false` when not. //! //! The command parser does not assume anything about the implementation //! of the textual interface. It provides a mechanism for parsing tokens //! that have been tokenized from an input and a method for communicating //! with the embedding application for errors and autocompletion by way of //! using structured data rather than printing to an output device (like //! `stdout`). //! //! The command parser consists of two important things: //! //! * A tree that represents the available commands and their arguments. //! This tree consists of instances of implementations of [`Node`] like //! [`CommandNode`], [`ParameterNode`] and [`RootNode`]. Construction of this //! tree is done with the help of [`CommandTree`], [`Command`] and //! [`Parameter`]. //! * A [`Parser`] that handles input and matches it against the command //! tree. This parser is intended to be short-lived and to just live //! for the duration of parsing and evaluating a single command line //! input. //! //! ## Building A Command Tree //! //! The commands handled by a [`Parser`] are represented by a tree based //! the words in the commands. For example, with commands `show directory`, //! `show class`, `help`, and `thread step`, there are 3 leaf nodes from //! the root and the tree is arranged like: //! //! * show //! * directory //! * class //! * help //! * thread //! * step //! //! Building a tree of nodes for use with the parser is best done with //! the [`CommandTree`] in conjunction with [`Command`] and [`Parameter`]. //! //! Start by creating a mutable [`CommandTree`] instance: //! //! ``` //! use commands::parser::{CommandTree, Parser}; //! //! let mut tree = CommandTree::new(); //! ``` //! //! Then, add your commands and arguments, and finally, //! call `finalize` on the tree to get back a [`RootNode`] //! that can use be used with a [`Parser`]. //! //! ``` //! use commands::parser::{Command, CommandTree, Parameter, Parser}; //! //! let mut tree = CommandTree::new(); //! tree.command(Command::new("again") //! .hidden(false) //! .parameter(Parameter::new("test") //! .required(false) //! .help("This is just a test parameter."))); //! let root = tree.finalize(); //! let mut parser = Parser::new(root); //! ``` //! //! [`commands::tokenizer`]: ../tokenizer/index.html //! [`Command`]: struct.Command.html //! [`CommandNode`]: struct.CommandNode.html //! [`CommandTree`]: struct.CommandTree.html //! [`Node`]: enum.Node.html //! [`Parameter`]: struct.Parameter.html //! [`ParameterNode`]: trait.ParameterNode.html //! [`Parser`]: struct.Parser.html //! [`RootNode`]: struct.RootNode.html //! [three kinds of parameters]: enum.ParameterKind.html mod builder; mod completion; mod constants; mod nodes; // Re-export public API pub use self::builder::{Command, CommandTree, Parameter}; pub use self::constants::ParameterKind; pub use self::constants::{PRIORITY_DEFAULT, PRIORITY_MINIMUM, PRIORITY_PARAMETER}; pub use self::completion::{Completion, CompletionOption}; pub use self::nodes::{Node, NodeOps, TreeNode}; pub use self::nodes::{CommandNode, ParameterNameNode, ParameterNode, RootNode}; use std::collections::HashMap; use std::error::Error; use std::fmt; use std::rc::Rc; use tokenizer::{Token, TokenType}; /// Command parser /// /// The lifetime parameter `'text` refers to the lifetime of the /// tokens passed into the parser. This is the same as the lifetime /// of the text used to create the tokens. /// /// When creating a `Parser`, you must give it an `Rc<RootNode>`. /// [`RootNode`] instances should be created using a [`CommandTree`]. /// /// ``` /// use commands::parser::{Command, CommandTree, Parser}; /// /// let mut tree = CommandTree::new(); /// tree.command(Command::new("show")); /// tree.command(Command::new("set")); /// tree.command(Command::new("help")); /// /// let mut parser = Parser::new(tree.finalize()); /// ``` /// /// The parser is constructed as a `mut`able object as most of /// the methods on it will modify its state. /// /// [`CommandTree`]: struct.CommandTree.html /// ['RootNode`]: struct.RootNode.html pub struct Parser<'text> { current_node: Rc<Node>, /// The nodes which have been accepted during `parse` or `advance`. pub nodes: Vec<Rc<Node>>, /// The tokens which have been accepted during `parse` or `advance`. pub tokens: Vec<Token<'text>>, commands: Vec<Rc<Node>>, parameters: HashMap<String, String>, } impl<'text> Parser<'text> { /// Construct a parser with a root node. pub fn new(initial_node: Rc<Node>) -> Parser<'text> { Parser { current_node: initial_node, nodes: vec![], tokens: vec![], commands: vec![], parameters: HashMap::new(), } } /// Given an optional token, get the possible valid completions /// for the current parser state. /// /// Possible completions are successors of the current node which /// are not `hidden`, are `acceptable`, and which match the token, /// if one has been provided. /// /// Nodes may customize the `Complete` trait to customize the /// [`Completion`] and [`CompletionOption`]s which are generated /// for that node. /// /// Each valid successor node will have one [`Completion`] in the /// result vector. Each [`Completion`] will have one or more /// [`CompletionOption`] for each valid way that the value may be /// entered. /// /// ``` /// use commands::parser::{Command, CommandTree, Parser}; /// use commands::tokenizer::{Token, tokenize}; /// /// let mut tree = CommandTree::new(); /// tree.command(Command::new("show")); /// tree.command(Command::new("set")); /// tree.command(Command::new("help")); /// /// let mut parser = Parser::new(tree.finalize()); /// /// // Completing now should have 3 options, 1 for each command. /// let comps = parser.complete(None); /// assert_eq!(comps.len(), 3); /// /// // But completing with a token for 'h' should have 1 option. /// if let Ok(tokens) = tokenize("h") { /// let comps = parser.complete(Some(tokens[0])); /// assert_eq!(comps.len(), 1); /// assert_eq!(comps[0].options.len(), 1); /// assert_eq!(comps[0].options[0].option_string, "help"); /// } else { /// panic!("Tokenize failed."); /// } /// /// // And completing for 's' should have 2 options. /// if let Ok(tokens) = tokenize("s") { /// let comps = parser.complete(Some(tokens[0])); /// assert_eq!(comps.len(), 2); /// } else { /// panic!("Tokenize failed."); /// } /// ``` /// /// [`Completion`]: struct.Completion.html /// [`CompletionOption`]: struct.CompletionOption.html pub fn complete(&self, token: Option<Token<'text>>) -> Vec<Completion> { self.current_node .successors() .iter() .filter(|n| { // To be a possible completion, the node should not be // hidden, it should be acceptable, and if there's a token, // it should be a valid match for the node. !n.node().hidden && n.acceptable(self, n) && if let Some(t) = token { n.matches(self, t) } else { true } }) .map(|n| n.complete(token)) .collect::<Vec<_>>() } /// Parse a vector of tokens, advancing through the /// node hierarchy. /// /// ``` /// use commands::parser::{Command, CommandTree, Parser}; /// use commands::tokenizer::tokenize; /// /// let mut tree = CommandTree::new(); /// tree.command(Command::new("show interface")); /// /// let mut parser = Parser::new(tree.finalize()); /// /// if let Ok(tokens) = tokenize("show interface") { /// parser.parse(tokens); /// } /// ``` pub fn parse(&mut self, tokens: Vec<Token<'text>>) -> Result<(), ParseError<'text>> { for token in tokens { match token.token_type { TokenType::Whitespace => {} TokenType::Word => try!(self.advance(token)), } } Ok(()) } /// Parse a single token, advancing through the node hierarchy. pub fn advance(&mut self, token: Token<'text>) -> Result<(), ParseError<'text>> { let matches = self.current_node .successors() .iter() .filter(|n| n.acceptable(self, n) && n.matches(self, token)) .cloned() .collect::<Vec<_>>(); match matches.len() { 1 => { let matching_node = &matches[0]; matching_node.accept(self, token, matching_node); self.current_node = matching_node.clone(); self.nodes.push(matching_node.clone()); self.tokens.push(token); Ok(()) } 0 => { Err(ParseError::NoMatches(token, self.current_node .successors() .iter() .filter(|n| n.acceptable(self, n)) .cloned() .collect::<Vec<_>>())) } _ => Err(ParseError::AmbiguousMatch(token, matches)), } } /// Execute the command that has been accepted by the parser. /// /// * XXX: This should be returning a Result probably. pub fn execute(&self) { if !self.commands.is_empty() { unimplemented!(); // self.commands[0].execute(self) } } /// Verify that the parser is in a valid state with /// respect to having accepted a command and all /// required parameters. pub fn verify(&self) -> Result<(), VerifyError> { if let Some(&Node::Command(ref command)) = self.commands.first().map(|n| &**n) { for expected in &command.parameters { if let Node::Parameter(ref param) = **expected { let name = ¶m.node.name; if param.required && !self.parameters.contains_key(name) { return Err(VerifyError::MissingParameter(name.clone())); } } else { unreachable!(); } } Ok(()) } else { Err(VerifyError::NoCommandAccepted) } } } /// Errors that calling `parse` on the `Parser` can raise. #[derive(Clone)] pub enum ParseError<'text> { /// There were no matches for the token. NoMatches(Token<'text>, Vec<Rc<Node>>), /// There was more than 1 possible match for the token. AmbiguousMatch(Token<'text>, Vec<Rc<Node>>), } impl<'text> fmt::Debug for ParseError<'text> { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { match *self { ParseError::NoMatches(token, _) => write!(f, "NoMatches({:?}, ...)", token), ParseError::AmbiguousMatch(token, _) => write!(f, "AmbiguousMatch({:?}, ...)", token), } } } impl<'text> Error for ParseError<'text> { fn description(&self) -> &str { match *self { ParseError::NoMatches(_, _) => "No match.", ParseError::AmbiguousMatch(_, _) => "Ambiguous match.", } } } impl<'text> fmt::Display for ParseError<'text> { fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { self.description().fmt(f) } } /// Errors that calling `verify` on the `Parser` can raise. #[derive(Clone,Debug)] pub enum VerifyError { /// No command has been accepted by the parser. NoCommandAccepted, /// A required parameter is missing. MissingParameter(String), } impl Error for VerifyError { fn description(&self) -> &str { match *self { VerifyError::NoCommandAccepted => "No command has been accepted by the parser.", VerifyError::MissingParameter(_) => "A required parameter is missing.", } } } impl fmt::Display for VerifyError { fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { self.description().fmt(f) } } #[cfg(test)] mod test { use super::*; use tokenizer::tokenize; #[test] #[should_panic] fn verify_signals_no_command() { let root = CommandTree::new().finalize(); let parser = Parser::new(root); match parser.verify() { Err(VerifyError::NoCommandAccepted) => panic!(), _ => {} } } #[test] #[should_panic] fn parse_signals_no_matches() { let mut tree = CommandTree::new(); tree.command(Command::new("show")); let mut parser = Parser::new(tree.finalize()); if let Ok(tokens) = tokenize("h") { match parser.parse(tokens) { Err(ParseError::NoMatches(_, _)) => panic!(), _ => {} } } } #[test] #[should_panic] fn parse_signals_ambiguous_match() { let mut tree = CommandTree::new(); tree.command(Command::new("show")); tree.command(Command::new("set")); let mut parser = Parser::new(tree.finalize()); if let Ok(tokens) = tokenize("s") { match parser.parse(tokens) { Err(ParseError::AmbiguousMatch(_, _)) => panic!(), _ => {} } } } }