// OPCUA for Rust
// SPDX-License-Identifier: MPL-2.0
// Copyright (C) 2017-2020 Adam Lock

//! Contains the implementation of `NumericRange`.

use std::str::FromStr;

use regex::Regex;

/// Numeric range describes a range within an array. See OPCUA Part 4 7.22
///
/// This parameter is defined in Table 159. A formal BNF definition of the numeric range can be
/// found in Clause A.3.
///
/// The syntax for the string contains one of the following two constructs. The first construct is
/// the string representation of an individual integer. For example, `6` is valid, but `6,0` and
/// `3,2` are not. The minimum and maximum values that can be expressed are defined by the use
/// of this parameter and not by this parameter type definition. The second construct is a range
/// represented by two integers separated by the colon (`:`) character. The first integer shall
/// always have a lower value than the second. For example, `5:7` is valid, while `7:5` and `5:5`
/// are not. The minimum and maximum values that can be expressed by these integers are defined by
/// the use of this parameter, and not by this parameter type definition. No other characters,
/// including white-space characters, are permitted.
///
/// Multi-dimensional arrays can be indexed by specifying a range for each dimension separated by
/// a `,`. For example, a 2x2 block in a 4x4 matrix could be selected with the range `1:2,0:1`.
/// A single element in a multi-dimensional array can be selected by specifying a single number
/// instead of a range. For example, `1,1` specifies selects the `[1,1]` element in a two dimensional
/// array.
///
/// Dimensions are specified in the order that they appear in the ArrayDimensions Attribute. All
/// dimensions shall be specified for a NumericRange to be valid.
///
/// All indexes start with `0`. The maximum value for any index is one less than the length of the
/// dimension.
#[derive(Debug, Clone, PartialEq)]
pub enum NumericRange {
    /// None
    None,
    /// A single index
    Index(u32),
    /// A range of indices
    Range(u32, u32),
    /// Multiple ranges contains any mix of Index, Range values - a multiple range containing multiple ranges is invalid
    MultipleRanges(Vec<NumericRange>),
}

impl NumericRange {
    pub fn has_range(&self) -> bool {
        *self != NumericRange::None
    }
}

// Valid inputs
#[test]
fn valid_numeric_ranges() {
    let valid_ranges = vec![
        ("", NumericRange::None, ""),
        ("0", NumericRange::Index(0), "0"),
        ("0000", NumericRange::Index(0), "0"),
        ("1", NumericRange::Index(1), "1"),
        ("0123456789", NumericRange::Index(123456789), "123456789"),
        ("4294967295", NumericRange::Index(4294967295), "4294967295"),
        ("1:2", NumericRange::Range(1, 2), "1:2"),
        ("2:3", NumericRange::Range(2, 3), "2:3"),
        ("0:1,0:2,0:3,0:4,0:5", NumericRange::MultipleRanges(vec![
            NumericRange::Range(0, 1),
            NumericRange::Range(0, 2),
            NumericRange::Range(0, 3),
            NumericRange::Range(0, 4),
            NumericRange::Range(0, 5)
        ]), "0:1,0:2,0:3,0:4,0:5"),
        ("0:1,2,3,0:4,5,6,7,8,0:9", NumericRange::MultipleRanges(vec![
            NumericRange::Range(0, 1),
            NumericRange::Index(2),
            NumericRange::Index(3),
            NumericRange::Range(0, 4),
            NumericRange::Index(5),
            NumericRange::Index(6),
            NumericRange::Index(7),
            NumericRange::Index(8),
            NumericRange::Range(0, 9)
        ]), "0:1,2,3,0:4,5,6,7,8,0:9")
    ];
    for vr in valid_ranges {
        let range = vr.0.parse::<NumericRange>();
        if range.is_err() {
            println!("Range {} is in error when it should be ok", vr.0);
        }
        assert!(range.is_ok());
        assert_eq!(range.unwrap(), vr.1);
        assert_eq!(vr.2, &vr.1.as_string());
    }
}

#[test]
fn invalid_numeric_ranges() {
    // Invalid values are either malformed, contain a min >= max, or they exceed limits on size of numbers
    // or number of indices.
    let invalid_ranges = vec![
        " ", " 1", "1 ", ":", ":1", "1:1", "2:1", "0:1,2,3,4:4", "1:", "1:1:2", ",", ":,", ",:",
        ",1", "1,", "1,2,", "1,,2", "01234567890", "0,1,2,3,4,5,6,7,8,9,10",
        "4294967296", "0:4294967296", "4294967296:0"
    ];
    for vr in invalid_ranges {
        println!("vr = {}", vr);
        let range = vr.parse::<NumericRange>();
        if range.is_ok() {
            println!("Range {} is ok when it should be in error", vr);
        }
        assert!(range.is_err());
    }
}

const MAX_INDICES: usize = 10;

impl FromStr for NumericRange {
    type Err = ();
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if s.is_empty() {
            Ok(NumericRange::None)
        } else {
            // <numeric-range> ::= <dimension> [',' <dimension>]
            // <dimension> ::= <index> [':' <index>]
            // <index> ::= <digit> [<digit>]
            // <digit> ::= '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'

            // Split the string on the comma
            let parts: Vec<_> = s.split(',').collect();
            match parts.len() {
                1 => Self::parse_range(&parts[0]),
                2..=MAX_INDICES => {
                    // Multi dimensions
                    let mut ranges = Vec::with_capacity(parts.len());
                    for p in &parts {
                        if let Ok(range) = Self::parse_range(&p) {
                            ranges.push(range);
                        } else {
                            return Err(());
                        }
                    }
                    Ok(NumericRange::MultipleRanges(ranges))
                }
                // 0 parts, or more than MAX_INDICES (really????)
                _ => Err(()),
            }
        }
    }
}

impl NumericRange {
    pub fn new<T>(s: T) -> Result<Self, ()> where T: Into<String> {
        Self::from_str(s.into().as_ref())
    }

    pub fn as_string(&self) -> String {
        match self {
            NumericRange::None => String::new(),
            NumericRange::Index(idx) => {
                format!("{}", idx)
            }
            NumericRange::Range(min, max) => {
                format!("{}:{}", min, max)
            }
            NumericRange::MultipleRanges(ref ranges) => {
                let ranges: Vec<String> = ranges.iter().map(|r| r.as_string()).collect();
                ranges.join(",")
            }
        }
    }

    fn parse_range(s: &str) -> Result<NumericRange, ()> {
        if s.is_empty() {
            Err(())
        } else {
            // Regex checks for number or number:number
            //
            // The BNF for numeric range doesn't appear to care that number could start with a zero,
            // e.g. 0009 etc. or have any limits on length.
            //
            // To stop insane values, a number must be 10 digits (sufficient for any permissible
            // 32-bit value) or less regardless of leading zeroes.
            lazy_static! {
                static ref RE: Regex = Regex::new("^(?P<min>[0-9]{1,10})(:(?P<max>[0-9]{1,10}))?$").unwrap();
            }
            if let Some(captures) = RE.captures(s) {
                let min = captures.name("min");
                let max = captures.name("max");
                match (min, max) {
                    (None, None) | (None, Some(_)) => Err(()),
                    (Some(min), None) => {
                        min.as_str().parse::<u32>()
                            .map(|min| NumericRange::Index(min))
                            .map_err(|_| ())
                    }
                    (Some(min), Some(max)) => {
                        // Parse as 64-bit but cast down
                        if let Ok(min) = min.as_str().parse::<u64>() {
                            if let Ok(max) = max.as_str().parse::<u64>() {
                                if min >= max {
                                    Err(())
                                } else if max > u32::MAX as u64 {
                                    Err(())
                                } else {
                                    Ok(NumericRange::Range(min as u32, max as u32))
                                }
                            } else {
                                Err(())
                            }
                        } else {
                            Err(())
                        }
                    }
                }
            } else {
                Err(())
            }
        }
    }

    /// Tests if the range is basically valid, i.e. that the min < max, that multiple ranges
    /// doesn't point to multiple ranges
    pub fn is_valid(&self) -> bool {
        match self {
            NumericRange::None => true,
            NumericRange::Index(_) => true,
            NumericRange::Range(min, max) => { min < max }
            NumericRange::MultipleRanges(ref ranges) => {
                let found_invalid = ranges.iter().any(|r| {
                    // Nested multiple ranges are not allowed
                    match r {
                        NumericRange::MultipleRanges(_) => true,
                        r => !r.is_valid()
                    }
                });
                !found_invalid
            }
        }
    }
}