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

use super::*;

pub enum Operator<T> 
where T: std::fmt::Display
{
  IsNull,
  IsNotNull,
  Equal(Value<T>),
  NotEqual(Value<T>),
  GreaterThan(Value<T>),
  GreaterEqual(Value<T>),
  LowerThan(Value<T>),
  LowerEqual(Value<T>),
}

/// Describe a single filtering condition using a label and an operator (with the associated operator value if applicable)
pub struct Condition<T>
where T: std::fmt::Display
{
  label: String,
  operator: Operator<T>,
}

impl<T> Condition<T>
where T: std::fmt::Display
{
  pub fn from_label_operator(label: String, operator: Operator<T>) -> Condition<T> {
    Condition { label, operator }
  }
}

impl<T> traits::Filter for Condition<T>
where T: std::fmt::Display
{
  /// Return the `WHERE` clause associated with the condition
  fn filter(&self) -> String {
    let label = &self.label;
    match &self.operator {
      Operator::IsNull          => format!("`{label}` IS NULL"),
      Operator::IsNotNull       => format!("`{label}` IS NOT NULL"),
      Operator::Equal(v)        => format!("`{label}` = {v}"),
      Operator::NotEqual(v)     => format!("`{label}` != {v}"),
      Operator::GreaterThan(v)  => format!("`{label}` > {v}"),
      Operator::GreaterEqual(v) => format!("`{label}` >= {v}"),
      Operator::LowerThan(v)    => format!("`{label}` < {v}"),
      Operator::LowerEqual(v)   => format!("`{label}` <= {v}"),
    }
  }
}

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

  #[test]
  fn it_display_correct_clause_for_u32() -> Result<()> {
    use traits::Filter;

    assert!(Field::from("key").eq(1u32).filter().eq("`key` = 1"));
    assert!(Field::from("key").ne(1u32).filter().eq("`key` != 1"));
    assert!(Field::from("key").gt(2u32).filter().eq("`key` > 2"));
    assert!(Field::from("key").ge(2u32).filter().eq("`key` >= 2"));
    assert!(Field::from("key").lt(2u32).filter().eq("`key` < 2"));
    assert!(Field::from("key").le(2u32).filter().eq("`key` <= 2"));

    Ok(())
  }

  #[test]
  fn it_display_correct_clause_for_string() -> Result<()> {
    use traits::Filter;

    assert!(Field::from("key_str").eq("val").filter().eq("`key_str` = 'val'"));
    assert!(Field::from("key_str").ne("val").filter().eq("`key_str` != 'val'"));
    assert!(Field::from("key_str").gt("val").filter().eq("`key_str` > 'val'"));
    assert!(Field::from("key_str").ge("val").filter().eq("`key_str` >= 'val'"));
    assert!(Field::from("key_str").lt("val").filter().eq("`key_str` < 'val'"));
    assert!(Field::from("key_str").le("val").filter().eq("`key_str` <= 'val'"));

    Ok(())
  }
}