1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135

use item::StringItem;

///
/// A builder for a tree of [`StringItem`]s
///
/// [`StringItem`]: ../item/struct.StringItem.html
pub struct TreeBuilder {
    item: StringItem,
    level: u32,
}

impl TreeBuilder {
    ///
    /// Start building a tree
    ///
    /// The `text` argument will be the top level item's text.
    ///
    pub fn new(text: String) -> TreeBuilder {
        TreeBuilder {
            item: StringItem {
                text,
                children: Vec::new(),
            },
            level: 0,
        }
    }

    fn append_child_level(parent: &mut StringItem, level: u32, item: StringItem) {
        if level == 0 {
            parent.children.push(item);
        } else {
            TreeBuilder::append_child_level(parent.children.last_mut().unwrap(), level - 1, item);
        }
    }

    ///
    /// Add a child to the current item and make the new child current
    ///
    pub fn begin_child(&mut self, text: String) -> &mut Self {
        TreeBuilder::append_child_level(
            &mut self.item,
            self.level,
            StringItem {
                text,
                children: Vec::new(),
            },
        );
        self.level += 1;
        self
    }

    ///
    /// Finish adding children, and make the current item's parent current
    ///
    pub fn end_child(&mut self) -> &mut Self {
        self.level -= 1;
        self
    }

    ///
    /// Add an empty child (leaf item) to the current item
    ///
    pub fn add_empty_child(&mut self, text: String) -> &mut Self {
        self.begin_child(text).end_child()
    }

    ///
    /// Finish building the tree and return the top level item
    ///
    pub fn build(&mut self) -> StringItem {
        self.item.clone()
    }
}

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

    #[test]
    fn empty() {
        let tree = TreeBuilder::new("test".to_string()).build();
        assert_eq!(&tree.text, "test");
        assert_eq!(tree.children.len(), 0);
    }

    #[test]
    fn single_child() {
        let tree = TreeBuilder::new("test".to_string())
            .add_empty_child("test_two".to_string())
            .build();

        assert_eq!(&tree.text, "test");
        assert_eq!(tree.children.len(), 1);
        assert_eq!(&tree.children[0].text, "test_two");
    }

    #[test]
    fn many_children_flat() {
        let mut builder = TreeBuilder::new("test".to_string());
        let n = 10;
        for i in 0..n {
            builder.add_empty_child(format!("test {}", i));
        }
        let tree = builder.build();

        assert_eq!(&tree.text, "test");
        assert_eq!(tree.children.len(), n);
        for i in 0..n {
            assert_eq!(tree.children[i].text, format!("test {}", i));
        }
    }

    #[test]
    fn many_children_nested() {
        let mut builder = TreeBuilder::new("test".to_string());
        let n = 10;
        for i in 0..n {
            builder.begin_child(format!("test {}", i));
        }
        for _ in 0..n {
            builder.end_child();
        }
        let tree = builder.build();

        assert_eq!(&tree.text, "test");

        let mut item = tree;
        for _ in 0..n {
            assert_eq!(item.children.len(), 1);
            item = item.children[0].clone();
        }

        assert_eq!(item.children.len(), 0);
    }
}