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Improve RVR Parsing (#10)
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@JonathanDowning
JonathanDowning authored Dec 4, 2020
1 parent 901bdff commit bb70b43
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3 changes: 2 additions & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -5,9 +5,10 @@ This is a simple regular expression based METAR parser.
## Usage Example

``` swift
let metar = METAR(rawMETAR: "EGLL 290420Z AUTO 05005KT 020V090 7000 OVC005 09/08 Q1024 TEMPO BKN004")
let metar = METAR(rawMETAR: "EGLL 290420Z AUTO 05005KT 020V090 7000 R04/1300VP2000U OVC005 09/08 Q1024 TEMPO BKN004")
print(metar?.visibility?.measurement) // Prints: Optional(7000.0 m)
print(metar?.temperature?.measurement) // Prints: Optional(9.0 °C)
print(metar?.qnh?.measurement) // Prints: Optional(1024.0 hPa)
print(metar?.wind?.speed.measurement) // Prints: Optional(5.0 kn)
print(metar?.runwayVisualRanges) // Prints: Optional([Runway 04: 1300.0 m – >2000.0 m Increasing])
```
98 changes: 75 additions & 23 deletions Sources/METAR/METAR.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -106,7 +106,7 @@ public extension METAR {
var metar = metar

guard let loneSlashesRegularExpression = try? NSRegularExpression(pattern: "^(/)+") else { return nil }
guard let icaoRegularExpression = try? NSRegularExpression(pattern: "(.*?)([A-Z]{4})\\b") else { return nil }
guard let icaoRegularExpression = try? NSRegularExpression(pattern: "(.*?)([A-Z0-9]{4})\\b") else { return nil }
guard let dateRegularExpression = try? NSRegularExpression(pattern: "(?<!\\S)([0-9]{2})([0-9]{2})([0-9]{2})Z\\b") else { return nil }
guard let remarksRegularExpression = try? NSRegularExpression(pattern: "(?<!\\S)RMK(.*)") else { return nil }
guard let tempoBecomingRegularExpression = try? NSRegularExpression(pattern: "(?<!\\S)(TEMPO|BECMG)(.*)") else { return nil }
Expand All @@ -124,7 +124,7 @@ public extension METAR {
guard let metricFractionVisibilityRegularExpression = try? NSRegularExpression(pattern: "(?<!\\S)(?:([0-9]+) )?([0-9]+)/([0-9]{1})SM\\b") else { return nil }
guard let weatherRegularExpression = try? NSRegularExpression(pattern: "(?<!\\S)(-|\\+|VC|RE)?([A-Z]{2})([A-Z]{2})?([A-Z]{2})?\\b") else { return nil }
guard let pressureRegularExpression = try? NSRegularExpression(pattern: "(?<!\\S)(?:(?:Q([0-9]{4}))|(?:A([0-9]{4})))\\b") else { return nil }
guard let rvrRegularExpression = try? NSRegularExpression(pattern: "(?<!\\S)R([0-9]{2}[L|C|R]?)\\/(?:(?:([P|M]?)([0-9]{4}))|(?:([0-9]{4})V([0-9]{4})))(FT)?(U|D|N)?\\b") else { return nil }
guard let rvrRegularExpression = try? NSRegularExpression(pattern: "\\bR([0-9]{2}[L|C|R]?)\\/([P|M]?)([0-9]{4})(?:V([P|M]?)([0-9]{4}))?(FT)?(U|D|N)?\\b") else { return nil }

// Lone Slashes Removal

Expand Down Expand Up @@ -242,25 +242,38 @@ public extension METAR {

var rvrs = [RunwayVisualRange]()
for match in metar.matches(for: rvrRegularExpression).reversed() {
guard let range = match[0], let runwayRange = match[1] else {
guard let range = match[0], let runwayRange = match[1], let visibilityValue = match[3].flatMap({ Double(String(metar[$0])) }) else {
continue
}

let unit: UnitLength = match[6].map { metar[$0] } == "FT" ? .feet : .meters

let visibility: RunwayVisualRange.Visibility
if let lower = match[4].flatMap({ Double(String(metar[$0])) }), let upper = match[5].flatMap({ Double(String(metar[$0])) }) {
visibility = .variable(.init(value: min(lower, upper), unit: unit), .init(value: max(lower, upper), unit: unit))
} else if let value = match[3].flatMap({ Double(String(metar[$0])) }), match[2].map({ metar[$0] }) == "M" {
visibility = .lessThan(.init(value: value, unit: unit))
} else if let value = match[3].flatMap({ Double(String(metar[$0])) }), match[2].map({ metar[$0] }) == "P" {
visibility = .greaterThan(.init(value: value, unit: unit))
} else if let value = match[3].flatMap({ Double(String(metar[$0])) }) {
visibility = .equal(.init(value: value, unit: unit))
} else {
continue
let visbilityModifier: RunwayVisualRange.Visibility.Modifier
switch match[2].map({ metar[$0] }) {
case "M":
visbilityModifier = .lessThan
case "P":
visbilityModifier = .greaterThan
default:
visbilityModifier = .equalTo
}

let visibility = RunwayVisualRange.Visibility(modifier: visbilityModifier, measurement: .init(value: visibilityValue, unit: unit))

let variableVisibility: RunwayVisualRange.Visibility? = match[5].flatMap({ Double(String(metar[$0])) }).map { value in
let variableVisibilityModifier: RunwayVisualRange.Visibility.Modifier
switch match[4].map({ metar[$0] }) {
case "M":
variableVisibilityModifier = .lessThan
case "P":
variableVisibilityModifier = .greaterThan
default:
variableVisibilityModifier = .equalTo
}
return .init(modifier: variableVisibilityModifier, measurement: .init(value: value, unit: unit))
}


let trend: RunwayVisualRange.Trend?
switch match[7].map({ metar[$0] }) {
case "U":
Expand All @@ -273,7 +286,7 @@ public extension METAR {
trend = nil
}

rvrs.append(.init(runway: String(metar[runwayRange]), visibility: visibility, trend: trend))
rvrs.append(.init(runway: String(metar[runwayRange]), visibility: visibility, variableVisibility: variableVisibility, trend: trend))

metar.removeSubrange(range)
}
Expand Down Expand Up @@ -640,23 +653,62 @@ public struct Visibility: Equatable {

}

public struct RunwayVisualRange: Equatable {
public struct RunwayVisualRange: Equatable, CustomStringConvertible {

public struct Visibility: Equatable, CustomStringConvertible {

public enum Visibility: Equatable {
case lessThan(Measurement<UnitLength>)
case equal(Measurement<UnitLength>)
case greaterThan(Measurement<UnitLength>)
case variable(Measurement<UnitLength>, Measurement<UnitLength>)
public enum Modifier {
case lessThan, equalTo, greaterThan
}

public var modifier: Modifier = .equalTo
public var measurement: Measurement<UnitLength>

public var description: String {
switch modifier {
case .lessThan:
return "<\(measurement)"
case .equalTo:
return "\(measurement)"
case .greaterThan:
return ">\(measurement)"
}
}
}

public enum Trend {
case increasing, decreasing, notChanging
public enum Trend: CustomStringConvertible {
case decreasing
case notChanging
case increasing

public var description: String {
switch self {
case .decreasing:
return "Decreasing"
case .notChanging:
return "Not Changing"
case .increasing:
return "Increasing"
}
}
}

public var runway: String
public var visibility: Visibility
public var variableVisibility: Visibility?
public var trend: Trend?

public var description: String {
var description = "Runway \(runway): \(visibility)"
if let variableVisibility = variableVisibility {
description += " – \(variableVisibility)"
}
if let trend = trend {
description += " \(trend)"
}
return description
}

}

public struct Wind: Equatable {
Expand Down
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