// testing.rs

//

// Copyright 2018 Georges Racinet <georges.racinet@octobus.net>

//

// This software may be used and distributed according to the terms of the

// GNU General Public License version 2 or any later version.

use crate::{Graph, GraphError, Revision, NULL_REVISION};

/// A stub `Graph`, same as the one from `test-ancestor.py`

///

/// o  13

/// |

/// | o  12

/// | |

/// | | o    11

/// | | |\

/// | | | | o  10

/// | | | | |

/// | o---+ |  9

/// | | | | |

/// o | | | |  8

///  / / / /

/// | | o |  7

/// | | | |

/// o---+ |  6

///  / / /

/// | | o  5

/// | |/

/// | o  4

/// | |

/// o |  3

/// | |

/// | o  2

/// |/

/// o  1

/// |

/// o  0

#[derive(Clone, Debug)]

pub struct SampleGraph;

impl Graph for SampleGraph {

    fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError> {

        let null_rev = NULL_REVISION.0;

        let res = match rev.0 {

            0 => Ok([null_rev, null_rev]),

            1 => Ok([0, null_rev]),

            2 => Ok([1, null_rev]),

            3 => Ok([1, null_rev]),

            4 => Ok([2, null_rev]),

            5 => Ok([4, null_rev]),

            6 => Ok([4, null_rev]),

            7 => Ok([4, null_rev]),

            8 => Ok([null_rev, null_rev]),

            9 => Ok([6, 7]),

            10 => Ok([5, null_rev]),

            11 => Ok([3, 7]),

            12 => Ok([9, null_rev]),

            13 => Ok([8, null_rev]),

            r => Err(GraphError::ParentOutOfRange(Revision(r))),

        };

        match res {

            Ok([a, b]) => Ok([Revision(a), Revision(b)]),

            Err(e) => Err(e),

        }

    }

}

// A Graph represented by a vector whose indices are revisions

// and values are parents of the revisions

pub type VecGraph = Vec<[Revision; 2]>;

impl Graph for VecGraph {

    fn parents(&self, rev: Revision) -> Result<[Revision; 2], GraphError> {

        Ok(self[rev.0 as usize])

    }

}