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// Conserve backup system.
// Copyright 2015, 2016, 2017 Martin Pool.

//! Bands are identified by a string like `b0001-0023`, represented by a `BandId` object.

use std::fmt;

use errors::*;


/// Identifier for a band within an archive, eg 'b0001' or 'b0001-0020'.
///
/// `BandId`s implement a total ordering `std::cmp::Ord`.
#[derive(Debug, PartialEq, Clone, Eq, PartialOrd, Ord)]
pub struct BandId {
    // TODO: Maybe don't store both the vec and the string?

    /// The sequence numbers at each tier.
    seqs: Vec<u32>,

    /// The pre-calculated string form for this id.
    string_form: String,
}

// TODO: Maybe a more concise debug form?


impl BandId {
    /// Makes a new BandId from a sequence of integers.
    pub fn new(seqs: &[u32]) -> BandId {
        assert!(seqs.len() > 0);
        BandId {
            seqs: seqs.to_vec(),
            string_form: BandId::make_string_form(seqs),
        }
    }

    /// Return the origin BandId.
    pub fn zero() -> BandId {
        BandId::new(&[0])
    }

    /// Return the next BandId at the same level as self.
    pub fn next_sibling(self: &BandId) -> BandId {
        let mut next_seqs = self.seqs.clone();
        next_seqs[self.seqs.len() - 1] += 1;
        BandId::new(&next_seqs)
    }

    /// Make a new BandId from a string form.
    pub fn from_string(s: &str) -> Result<BandId> {
        let nope = Err(ErrorKind::InvalidVersion.into());
        if !s.starts_with('b') {
            return nope;
        }
        let mut seqs = Vec::<u32>::new();
        for num_part in s[1..].split('-') {
            match num_part.parse::<u32>() {
                Ok(num) => seqs.push(num),
                Err(..) => return nope,
            }
        }
        if seqs.is_empty() {
            nope
        } else {
            // This rebuilds a new string form to get it into the canonical form.
            Ok(BandId::new(&seqs))
        }
    }

    /// Returns the string representation of this BandId.
    ///
    /// Bands have an id which is a sequence of one or more non-negative integers.
    /// This is externally represented as a string like `b0001-0010`, which becomes
    /// their directory name in the archive.
    ///
    /// Numbers are zero-padded to what should normally be a reasonable length, but they can
    /// be longer.
    pub fn as_string(self: &BandId) -> &String {
        &self.string_form
    }

    fn make_string_form(seqs: &[u32]) -> String {
        let mut result = String::with_capacity(30);
        result.push_str("b");
        for s in seqs {
            result.push_str(&format!("{:04}-", s));
        }
        result.pop(); // remove the last dash
        result.shrink_to_fit();
        result
    }
}


impl fmt::Display for BandId {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.as_string().fmt(f)
    }
}


#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    #[should_panic]
    fn empty_id_not_allowed() {
        BandId::new(&[]);
    }

    #[test]
    fn equality() {
        assert_eq!(BandId::new(&[1]), BandId::new(&[1]))
    }

    #[test]
    fn zero() {
        assert_eq!(BandId::zero().as_string(), "b0000");
    }

    #[test]
    fn next() {
        assert_eq!(BandId::zero().next_sibling().as_string(), "b0001");
        assert_eq!(BandId::new(&[2, 3]).next_sibling().as_string(),
                   "b0002-0004");
    }

    #[test]
    fn as_string() {
        let band_id = BandId::new(&[1, 10, 20]);
        assert_eq!(band_id.as_string(), "b0001-0010-0020");
        assert_eq!(BandId::new(&[1000000, 2000000]).as_string(),
                   "b1000000-2000000")
    }

    #[test]
    fn from_string_detects_invalid() {
        assert!(BandId::from_string("").is_err());
        assert!(BandId::from_string("hello").is_err());
        assert!(BandId::from_string("b").is_err());
        assert!(BandId::from_string("b-").is_err());
        assert!(BandId::from_string("b2-").is_err());
        assert!(BandId::from_string("b-2").is_err());
        assert!(BandId::from_string("b2-1-").is_err());
        assert!(BandId::from_string("b2--1").is_err());
        assert!(BandId::from_string("beta").is_err());
        assert!(BandId::from_string("b-eta").is_err());
        assert!(BandId::from_string("b-1eta").is_err());
        assert!(BandId::from_string("b-1-eta").is_err());
    }

    #[test]
    fn from_string_valid() {
        assert_eq!(BandId::from_string("b0001").unwrap().as_string(), "b0001");
        assert_eq!(BandId::from_string("b123456").unwrap().as_string(),
                   "b123456");
        assert_eq!(BandId::from_string("b0001-0100-0234").unwrap().as_string(),
                   "b0001-0100-0234");
    }

    #[test]
    fn format() {
        let a_bandid = BandId::from_string("b0001-0234").unwrap();
        assert_eq!(format!("{}", a_bandid), "b0001-0234");
        // Implements padding correctly
        assert_eq!(format!("{:<15}", a_bandid), "b0001-0234     ");
    }
}