draconic/src/reader.rs

use std::fs::File;
use std::io::Read;
use std::path::Path;



// TODO: Make this work on only a predetermined size of a buffer.


/// Stores some input and allows it to be
/// read on a character by character basis.
///
pub struct Reader
{
   /// The current position in the buffer.
   position: usize,

   /// The buffer of the input data to be read.
   buffer: Vec<char>
}



impl Reader
{
   /// Create a new empty Reader.
   pub fn new() -> Reader
   {
      Reader
      {
         position: 0usize,
         buffer: Vec::new(),
      }
   }

   /// Create a new reader from a File.
   pub fn from_file<F>(filepath: F) -> Reader
      where F: AsRef<Path>
   {
      let mut reader: Reader;

      // Create a new Reader and load the data
      // for it from the file at the given filepath.
      reader = Reader::new();
      reader.load_from_file(filepath);

      reader
   }

   /// Create a new reader from a String.
   pub fn from_string(data: String) -> Reader
   {
      let mut reader: Reader;

      // Create a new Reader and load the data to it.
      reader = Reader::new();
      reader.load_from_string(data);

      reader
   }

   /// Reset the Reader back to the starting position.
   pub fn reset(&mut self)
   {
      // Move back to the start of the buffer.
      self.position = 0usize;
   }

   /// Clear the Reader of all data.
   pub fn clear(&mut self)
   {
      self.buffer = Vec::new();
      self.reset();
   }

   /// Clears the Reader and sets it to read from a File.
   pub fn load_from_file<F>(&mut self, filepath: F)
      where F: AsRef<Path>
   {
      let mut data: String;

      // Open the file for reading and load the
      // data into a String that will be parsed.
      data = String::new();
      match File::open(filepath.as_ref())
      {
         Ok(mut file) =>
         {
            match file.read_to_string(&mut data)
            {
               Ok(bytes_read) =>
               {
                  info!("{} bytes read from {:?}",
                        bytes_read, filepath.as_ref());
               }

               Err(error) =>
               {
                  error!("{}", error);
               }
            }
         }

         Err(error) =>
         {
            error!("{}", error);
         }
      }

      // Load the String read from the file.
      self.load_from_string(data);
   }

   /// Clears the Reader and sets it to read from the given data.
   pub fn load_from_string(&mut self, data: String)
   {
      // Clear the Reader.
      self.clear();

      // Parse the String that the reader is
      // reading from as a set of characters
      // in the Reader's buffer.
      for character in data.chars()
      {
         self.buffer.push(character);
      }
   }

   /// Get the current character.
   pub fn get_char(&self) -> Result<char, &'static str>
   {
      // Make sure we are not at the end of the buffer.
      if self.is_eob() == false
      {
         // Return the character at the current position.
         Ok(self.buffer[self.position])
      }
      else
      {
         // There was an error.
         Err("Unable to read character. \
              No characters left in the input buffer.")
      }
   }

   /// Get the current character and move the
   /// Reader on to the next character.
   pub fn consume_char(&mut self) -> Result<char, &'static str>
   {
      let character: char;

      // Get the current character and move the position 
      // in the buffer forward.
      character = try!(self.get_char());
      self.position += 1;

      // Return the character that was retrieved.
      Ok(character)
   }

   /// Get a line of text from the current character to the next
   /// newline character, including the current character.
   pub fn get_line(&mut self) -> Result<String, &'static str>
   {
      let mut index: usize;
      let mut buffer: String;

      // Create a new buffer to hold the line created.
      buffer = String::new();

      // Now get the current position the reader is at.
      index = self.position;
      while index < self.buffer.len() && self.buffer[index] != '\n'
      {
         buffer.push(self.buffer[index]);
         index += 1;
      }

      // Read the newline character if the reader did not run out of buffer.
      if index < self.buffer.len() && self.buffer[index] == '\n'
      {
         buffer.push(self.buffer[index]);
      }

      // Return the buffer of characters that was created.
      Ok(buffer)
   }

   /// Get a line of text from the current character to the next
   /// newline character, including the current character and newline.
   /// This will consume all the characters and move the position
   /// of the reader.
   pub fn consume_line(&mut self) -> Result<String, &'static str>
   {
      let mut continue_consuming: bool;
      let mut current_char: char;
      let mut buffer: String;

      // Create a new buffer to hold the line created.
      buffer = String::new();

      // Consume all the characters of the line
      // and add them to the buffer.
      continue_consuming = true;
      while continue_consuming == true
      {
         current_char = try!(self.consume_char());
         buffer.push(current_char);

         if current_char == '\n'
         {
            continue_consuming = false;
         }
      }

      // Return the buffer of characters that was created.
      Ok(buffer)
   }

   /// Check to see if we have reached the end of the buffer.
   pub fn is_eob(&self) -> bool
   {
      self.position >= self.buffer.len()
   }
}