//! A parser for the [TGFF][1] (Task Graphs For Free) format.
//!
//! [1]: http://ziyang.eecs.umich.edu/~dickrp/tgff/

use std::fmt;
use std::iter::Peekable;
use std::str::CharIndices;

pub use content::Content;
pub use content::{Graph, Task, Arc, Deadline};
pub use content::{Table, Column};

mod content;

static READ_CAPACITY: usize = 20;

/// An outcome of parsing.
pub type Result<T> = std::result::Result<T, Error>;

/// A parsing error.
pub struct Error {
    /// The line on which the error occurred.
    pub line: usize,
    /// The description of the error.
    pub message: String,
}

struct Parser<'a> {
    line: usize,
    cursor: Peekable<CharIndices<'a>>,
    content: Content,
}

/// Parse a string containing a TGFF file.
///
/// The input string is the content of a TGFF file generated by the `tgff`
/// command-line utility based on the corresponding TGFFOPT file.
pub fn parse(input: &str) -> Result<Content> {
    Parser::new(input).process()
}

macro_rules! raise(
    ($parser:expr, $($arg:tt)*) => (
        return Err(Error { line: $parser.line, message: format!($($arg)*) });
    );
);

macro_rules! some(
    ($parser:expr, $result:expr, $($arg:tt)*) => (
        match $result {
            Some(result) => result,
            _ => raise!($parser, $($arg)*),
        }
    );
);

impl fmt::Debug for Error {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        write!(formatter, "{} on line {}", self.message, self.line)
    }
}

impl fmt::Display for Error {
    #[inline]
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        fmt::Debug::fmt(self, formatter)
    }
}

impl<'a> Parser<'a> {
    fn new(input: &'a str) -> Parser<'a> {
        Parser {
            line: 1,
            cursor: input.char_indices().peekable(),
            content: content::new(),
        }
    }

    fn process(&mut self) -> Result<Content> {
        loop {
            match self.peek() {
                Some('@') => try!(self.process_at()),
                Some(_) => raise!(self, "found an unknown statement"),
                _ => break,
            }
        }
        Ok(std::mem::replace(&mut self.content, content::new()))
    }

    fn process_at(&mut self) -> Result<()> {
        try!(self.skip_char('@'));

        let name = try!(self.get_token());
        let number = try!(self.get_natural());

        if let Some('{') = self.peek() {
            self.process_block(name, number)
        } else {
            self.content.attributes.insert(name, number);
            Ok(())
        }
    }

    fn process_block(&mut self, name: String, id: usize) -> Result<()> {
        try!(self.skip_char('{'));
        if let Some('#') = self.peek() {
            try!(self.process_table(name, id));
        } else {
            try!(self.process_graph(name, id));
        }
        try!(self.skip_char('}'));
        Ok(())
    }

    fn process_graph(&mut self, name: String, id: usize) -> Result<()> {
        let mut graph = content::new_graph(name, id);

        loop {
            match self.read_token() {
                Some(token) => match &*token {
                    "TASK" => {
                        let id = try!(self.get_id());
                        try!(self.skip_str("TYPE"));
                        let kind = try!(self.get_natural());
                        graph.tasks.push(content::new_task(id, kind));
                    },
                    "ARC" => {
                        let id = try!(self.get_id());
                        try!(self.skip_str("FROM"));
                        let from = try!(self.get_id());
                        try!(self.skip_str("TO"));
                        let to = try!(self.get_id());
                        try!(self.skip_str("TYPE"));
                        let kind = try!(self.get_natural());
                        graph.arcs.push(content::new_arc(id, from, to, kind));
                    },
                    "HARD_DEADLINE" => {
                        let id = try!(self.get_id());
                        try!(self.skip_str("ON"));
                        let on = try!(self.get_id());
                        try!(self.skip_str("AT"));
                        let at = try!(self.get_natural());
                        graph.deadlines.push(content::new_deadline(id, on, at));
                    },
                    _ => {
                        let value = try!(self.get_natural());
                        graph.attributes.insert(token.clone(), value);
                    },
                },
                _ => break,
            }
        }

        self.content.graphs.push(graph);
        Ok(())
    }

    fn process_table(&mut self, name: String, id: usize) -> Result<()> {
        let mut table = content::new_table(name, id);

        try!(self.skip_char('#'));

        let mut names = vec![];
        loop {
            match self.read_token() {
                Some(token) => names.push(token),
                _ => break,
            }
        }
        for name in names.into_iter() {
            table.attributes.insert(name, try!(self.get_real()));
        }

        try!(self.skip_comment());
        try!(self.skip_char('#'));

        loop {
            match self.read_token() {
                Some(name) => table.columns.push(content::new_column(name)),
                _ => break,
            }
        }
        let cols = table.columns.len();
        loop {
            match self.peek() {
                Some('}') | None => break,
                _ => {},
            }
            for i in (0..cols) {
                table.columns[i].data.push(try!(self.get_real()));
            }
        }

        self.content.tables.push(table);
        Ok(())
    }

    #[inline]
    fn peek(&mut self) -> Option<char> {
        match self.cursor.peek() {
            Some(&(_, c)) => Some(c),
            _ => None,
        }
    }

    fn skip(&mut self, accept: &Fn(usize, char) -> bool) -> usize {
        let mut count = 0;

        loop {
            match self.peek() {
                Some(c) => {
                    if !accept(count, c) { break; }
                    self.next();
                    count += 1;
                },
                _ => break,
            }
        }

        count
    }

    fn skip_char(&mut self, expected: char) -> Result<()> {
        match self.next() {
            Some(c) => {
                if c == expected {
                    self.skip_void();
                    return Ok(());
                }
            },
            _ => {},
        }
        raise!(self, "expected `{}`", expected);
    }

    fn skip_str(&mut self, expected: &str) -> Result<()> {
        let (len, vec) = (expected.len(), expected.chars().collect::<Vec<_>>());
        if self.skip(&|i, c| i < len && c == vec[i]) != len {
            raise!(self, "expected `{}`", expected);
        }
        self.skip_void();
        Ok(())
    }

    #[inline]
    fn skip_void(&mut self) {
        self.skip(&|_, c| c == ' ' || c == '\t' || c == '\n');
    }

    fn skip_comment(&mut self) -> Result<()> {
        if self.skip(&|i, c| i == 0 && c == '#' || (i > 0) && c == '-') < 2 {
            raise!(self, "expected a comment line");
        }
        self.skip_void();
        Ok(())
    }

    fn read(&mut self, accept: &Fn(usize, char) -> bool) -> Option<String> {
        let mut result = std::string::String::with_capacity(READ_CAPACITY);
        let mut count = 0;

        loop {
            match self.peek() {
                Some(c) => {
                    if !accept(count, c) { break; }
                    result.push(c);
                    self.next();
                    count += 1;
                },
                _ => break,
            }
        }

        if count == 0 {
            None
        } else {
            Some(result)
        }
    }

    fn read_token(&mut self) -> Option<String> {
        let result = self.read(&|i, c| {
            match c {
                'A'...'Z' | 'a'...'z' if i == 0 => true,
                'A'...'Z' | 'a'...'z' | '_' | '0'...'9' if i > 0 => true,
                _ => false,
            }
        });
        self.skip_void();
        result
    }

    fn read_id(&mut self) -> Option<usize> {
        match self.read_token() {
            Some(token) => match token.split('_').nth(1) {
                Some(id) => match usize::from_str_radix(id, 10) {
                    Ok(id) => Some(id),
                    _ => None,
                },
                _ => None,
            },
            _ => None,
        }
    }

    fn read_natural(&mut self) -> Option<usize> {
        let result = match self.read(&|_, c| c >= '0' && c <= '9') {
            Some(number) => match usize::from_str_radix(&number, 10) {
                Ok(number) => Some(number),
                _ => None,
            },
            _ => None,
        };
        self.skip_void();
        result
    }

    fn read_real(&mut self) -> Option<f64> {
        let result = match self.read(&|_, c| {
            match c {
                '+' | '-' | '.' | '0'...'9' | 'e' | 'E' => true,
                _ => false,
            }
        }) {
            Some(number) => match number.parse() {
                Ok(number) => Some(number),
                _ => None,
            },
            _ => None,
        };
        self.skip_void();
        result
    }

    fn get_token(&mut self) -> Result<String> {
        match self.read_token() {
            Some(token) => Ok(token),
            _ => raise!(self, "expected a token"),
        }
    }

    fn get_id(&mut self) -> Result<usize> {
        match self.read_id() {
            Some(id) => Ok(id),
            _ => raise!(self, "expected an id"),
        }
    }

    fn get_natural(&mut self) -> Result<usize> {
        match self.read_natural() {
            Some(number) => Ok(number),
            _ => raise!(self, "expected a natural number"),
        }
    }

    fn get_real(&mut self) -> Result<f64> {
        match self.read_real() {
            Some(number) => Ok(number),
            _ => raise!(self, "expected a real number"),
        }
    }
}

impl<'a> std::iter::Iterator for Parser<'a> {
    type Item = char;

    fn next(&mut self) -> Option<char> {
        match self.cursor.next() {
            Some((_, '\n')) => {
                self.line += 1;
                Some('\n')
            },
            Some((_, c)) => Some(c),
            _ => None,
        }
    }
}

#[cfg(test)]
mod tests {
    macro_rules! parser(
        ($input:expr) => (super::Parser::new($input));
    );

    #[test]
    fn process_at() {
        assert!(parser!("@abc 12").process_at().is_ok());
        assert!(parser!("@ ").process_at().is_err());
        assert!(parser!("@abc").process_at().is_err());
    }

    #[test]
    fn process_block() {
        assert!(parser!("{}").process_block(String::new(), 0).is_ok());
    }

    #[test]
    fn process_graph() {
        let mut parser = parser!("TASK t0_0\tTYPE 2   ");
        assert!(parser.process_graph(String::new(), 0).is_ok());
        {
            let ref task = parser.content.graphs[0].tasks[0];
            assert_eq!(task.id, 0);
            assert_eq!(task.kind, 2);
        }

        parser = parser!("ARC a0_42 \tFROM t0_0  TO  t0_1 TYPE 35   ");
        assert!(parser.process_graph(String::new(), 0).is_ok());
        {
            let ref arc = parser.content.graphs[0].arcs[0];
            assert_eq!(arc.id, 42);
            assert_eq!(arc.from, 0);
            assert_eq!(arc.to, 1);
            assert_eq!(arc.kind, 35);
        }

        parser = parser!("HARD_DEADLINE d0_9 ON t0_12 AT 1000   ");
        assert!(parser.process_graph(String::new(), 0).is_ok());
        {
            let ref deadline = parser.content.graphs[0].deadlines[0];
            assert_eq!(deadline.id, 9);
            assert_eq!(deadline.on, 12);
            assert_eq!(deadline.at, 1000);
        }
    }

    #[test]
    fn process_table() {
        let mut parser = parser!("# foo\n 70.07\n#--\n# bar baz\n1 2 3 4 ");
        assert!(parser.process_table(String::new(), 0).is_ok());
        let ref table = parser.content.tables[0];
        assert_eq!(table.attributes["foo"], 70.07);
        assert_eq!(table.columns[0].name, "bar".to_string());
        assert_eq!(table.columns[1].name, "baz".to_string());
        assert_eq!(table.columns[0].data, vec![1.0, 3.0]);
        assert_eq!(table.columns[1].data, vec![2.0, 4.0]);
    }

    #[test]
    fn skip_char() {
        let mut parser = parser!("#  \t\n  abc");
        assert!(parser.skip_char('#').is_ok());
        assert_eq!(parser.next().unwrap(), 'a');
    }

    #[test]
    fn skip_str() {
        let mut parser = parser!("abc  \t\n  xyz");
        assert!(parser.skip_str("abc").is_ok());
        assert_eq!(parser.next().unwrap(), 'x');
    }

    #[test]
    fn skip_void() {
        let mut parser = parser!("  \t  abc");
        parser.skip_void();
        assert_eq!(parser.next().unwrap(), 'a');
    }

    #[test]
    fn skip_comment() {
        let mut parser = parser!("#--------------   \n abc");
        assert!(parser.skip_comment().is_ok());
        assert_eq!(parser.next().unwrap(), 'a');
    }

    #[test]
    fn get_token() {
        macro_rules! test(
            ($input:expr, $output:expr) => (
                assert_eq!(parser!($input).get_token().unwrap(), $output.to_string())
            );
        );
        test!("AZ xyz", "AZ");
        test!("az xyz", "az");
        test!("AZ_az_09 xyz", "AZ_az_09");
    }

    #[test]
    fn get_id() {
        assert_eq!(parser!("t0_42").get_id().unwrap(), 42);
    }

    #[test]
    fn get_natural() {
        assert_eq!(parser!("09").get_natural().unwrap(), 9);
    }

    #[test]
    fn get_real() {
        macro_rules! test(
            ($input:expr, $output:expr) => (
                assert_eq!(parser!($input).get_real().unwrap(), $output)
            );
        );
        test!("-1", -1.0);
        test!("0.1", 0.1);
        test!("1.2e3", 1.2e3);
        test!("1.2e+3", 1.2e3);
        test!("-1.2e-3", -1.2e-3);
    }
}