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-- ************Purpose		:AMIN (Approximate Matching of Indian Names)
-- ************Developed by	: Technical Team Election, Commission of India, New Delhi.

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Imports System.Text.RegularExpressions
Public Class AMIN
Dim i As Integer
    Dim j As Integer
    Dim source() As Char
    Dim target() As Char
    Dim Simplificationcost As Decimal
    Function AMIN_percentage(ByVal strsource As String, ByVal strtarget As String) As Decimal
        Dim decPercentage As Decimal
        Dim len1 As Integer = Len(strsource)
        Dim len2 As Integer = Len(strtarget)
       
        Dim max As Integer
        max = Math.Max(len1, len2)
        decPercentage = System.Math.Round((1.0 - ((CDec(AMIN_English(strsource, strtarget)) / max))) * 100, 2)
        Return decPercentage
    End Function
    'ASSUMPTION IS THAT THE NAME STRINGS ARE CLEAN AND IN UPPERCASE 
    Function AMIN_English(ByVal str1 As String, ByVal str2 As String)
        Dim d(Len(str1), Len(str2)) As Decimal
        Dim i As Integer
        Dim j As Integer
        Dim value1 As Decimal
        Dim value2 As Decimal
        Dim value3 As Decimal
        Dim minValue As Decimal
        'Building Source array
        str1 = "#" & str1 & "!"
        source = str1.ToCharArray
        '******************
        'Building Target array
        str2 = "#" & str2 & "!"
        target = str2.ToCharArray
        '******************
        

        Dim len1 As Integer = str1.Length - 2
        Dim len2 As Integer = str2.Length - 2

        For i = 0 To len1
            d(i, 0) = i
        Next
        For j = 0 To len2
            d(0, j) = j
        Next
        For i = 1 To len1
            For j = 1 To len2
                Dim values(2) As Decimal
                value1 = d(i - 1, j) + costInsertDelete_EN(source(i), source(i - 1), source(i + 1)) 'cost deletion
                value2 = d(i, j - 1) + costInsertDelete_EN(target(j), target(j - 1), target(j + 1)) 'cost insertion
                minValue = Math.Min(value1, value2)
                value3 = d(i - 1, j - 1) + costsubstitution_EN(source(i), target(j)) 'cost substitution
                minValue = Math.Min(value3, minValue)
                d(i, j) = minValue
                ReDim Preserve values(1)
                If (i > 2 And j > 2) Then
                    If source(i) = target(j - 1) And source(i - 1) = target(j) Then
                        values(0) = d(i, j)
                        values(1) = d(i - 2, j - 2) + costswapping_EN(source(i), target(j))
                        d(i, j) = Min(values)
                    End If
                End If
                ReDim Preserve values(1)
                ReDim Preserve values(1)
                '"KS" is treated almost equal to "X"
                'value of matrix differs where KS is matched with X and it is different when X is matched with KS
                ' as length row and columns differs in both cases
                'that is why two cases are handled differently.
                Simplificationcost = 0.95
                If source(i) = "S" And source(i - 1) = "K" Then
                    If target(j) = "X" Then
                        values(0) = d(i, j)
                        If d(i - 1, j - 1) > 0.95 Then
                            values(1) = d(i - 1, j - 1) - Simplificationcost
                        Else
                            values(1) = d(i, j - 1) - Simplificationcost
                        End If
                        d(i, j) = Min(values)
                    End If
                ElseIf target(j) = "S" Then
                    If target(j - 1) = "K" And source(i) = "X" Then
                        values(0) = d(i, j)
                        ' values(1) = d(i - 1, j - 1) - SimplificationCost
                        values(1) = d(i, j - 1) - Simplificationcost
                        d(i, j) = Min(values)
                    End If
                End If
                '"EE" is treated almost equal to "I"
                If source(i) = "E" And source(i - 1) = "E" Then
                    If j = i - 1 Then
                        If target(j) = "I" Then
                            values(0) = d(i, j)
                            If j > 1 Then
                                Simplificationcost = 0.2 'cost is less if case occurs in between
                            Else
                                Simplificationcost = 0.95 'cost is more if case occurs at the start of word
                            End If
                            'If d(i - 1, j - 1) < 0.3 Then SimplificationCost = 0
                            values(1) = d(i - 1, j - 1) - Simplificationcost
                            d(i, j) = Min(values)
                        End If
                    End If
                    '"OO" is treated almost equal to "O"
                ElseIf source(i) = "O" And source(i - 1) = "O" Then
                    If j = i - 1 Then
                        If target(j) = "U" Then
                            values(0) = d(i, j)
                            If j > 1 Then
                                Simplificationcost = 0.2
                            Else
                                Simplificationcost = 0.95
                            End If
                            'If d(i - 1, j - 1) < 0.3 Then SimplificationCost = 0
                            values(1) = d(i - 1, j - 1) - Simplificationcost
                            d(i, j) = Min(values)
                        End If
                    End If
                ElseIf target(j) = "E" And target(j - 1) = "E" Then
                    If i = j - 1 Then
                        If source(i) = "I" Then
                            values(0) = d(i, j)
                            If i > 1 Then
                                Simplificationcost = 0.2
                            Else
                                Simplificationcost = 0.95
                            End If
                            ' If d(i - 1, j - 1) < 0.3 Then SimplificationCost = 0
                            values(1) = d(i - 1, j - 1) - Simplificationcost
                            d(i, j) = Min(values)
                        End If
                    End If
                ElseIf target(j) = "O" And target(j - 1) = "O" Then
                    If i = j - 1 Then
                        If source(i) = "U" Then
                            values(0) = d(i, j)
                            If i > 1 Then
                                Simplificationcost = 0.2 'cost is less if case occurs in between
                            Else
                                Simplificationcost = 0.95 'cost is more if case occurs at the start of word
                            End If
                            'If d(i - 1, j - 1) < 0.3 Then SimplificationCost = 0
                            values(1) = d(i - 1, j - 1) - Simplificationcost

                            d(i, j) = Min(values)
                        End If
                    End If
                End If
            Next
        Next
        Dim intdist As Decimal
        intdist = d(len1, len2)
        source.Clear(source, 0, source.Length)
        target.Clear(target, 0, target.Length)
        buildtable(d)
        Return intdist
    End Function
    'This function can be used in substitution of two characters based on the requirement for example: GY-JN for hindi 
    Function twoCharacterSubstitution(ByVal srcValue As String, ByVal targetValue As String)
        Return 0.0
    End Function
    Function isNearbyFirstChar_EN(ByVal char1 As Char, ByVal char1Next As Char, ByVal char2 As Char, ByVal char2Next As Char) As Boolean
        If char1 = char2 Then Return True
        If IsVowel(char1) And IsVowel(char2) And IsValidVowelCombination(char1, char2) Then Return True
        Select Case char1 & char1Next & char2
            Case "ESS", "YOU", "YUU", "GNN", "PSS"
                Return True
        End Select
        Select Case char1 & char2 & char2Next
            Case "SES", "UYO", "UYU", "NGN", "SPS"
                Return True
        End Select
        Select Case char1 & char2
            Case "CK", "KC", "KQ", "QK", "PF", "FP", "GJ", "JG", "BV", "VB", "VW", "WV", "BW", "WB", "JZ", "ZJ", "XZ", "ZX", "XS", "SX", "ZS", "SZ", "SC", "CS", "YU", "UY"
                Return True
            Case Else
                Return False
        End Select
    End Function
    Function IsValidVowelCombination(ByVal char1 As Char, ByVal char2 As Char) As Boolean
        'following are not the nearest combinations of vowels 
        Select Case char1 & char2
            Case "AU", "UA", "EU", "UE", "IU", "UI", "IO", "OI"
                Return False
            Case Else
                Return True
        End Select
    End Function
    Private Function costInsertDelete_EN(ByVal thischar As Char, ByVal prevchar As Char, ByVal nextchar As Char)
        'Cost Insertion for the Target Character and cost deletion for the source character
        If Asc(thischar) < 65 Or Asc(thischar) > 90 Then
            Return 0.05
        ElseIf (thischar = prevchar) And thischar <> "E" And thischar <> "O" Then
            'ElseIf (thischar = prevchar) Then
            Return 0.15
        End If
        If IsVowel(thischar) Then
            Return 0.25
        ElseIf Regex.IsMatch(thischar, "[WY]") = True Then
            Return 0.5
        ElseIf thischar = "H" Then
            If Regex.IsMatch(prevchar, "[BCDGKPJS]") = True Then
                Return 0.15
            Else
                Return 0.25
            End If
        ElseIf thischar = "C" And Regex.IsMatch(prevchar, "[SX]") = True Then
            Return 0.25
        ElseIf thischar = "N" And IsConsonant(nextchar) Then
            Return 0.35
        Else
            Return 1.0
        End If
    End Function
    Private Function costsubstitution_EN(ByVal chr1 As Char, ByVal chr2 As Char) As Decimal
        'cost of substituting source character with target character, only if the substitution is valid
        If chr1 = chr2 Then
            Return 0.0
        ElseIf IsVowel(chr1) And IsVowel(chr2) And IsValidVowelCombination(chr1, chr2) Then
            Return 0.25
        ElseIf (Asc(chr1) < 65 Or Asc(chr1) > 90) Or (Asc(chr2) < 65 Or Asc(chr2) > 90) Then
            Return 0.05
        End If
        Select Case chr1 & chr2
            Case "YI", "IY", "RD", "DR", "CK", "KC", "CS", "SC", "GJ", "JG", "ZJ", "JZ", "XZ", "ZX", "XS", "SX", "XJ", "JS", "SZ", "ZS"
                Return 0.25
            Case "KQ", "QK", "WV", "VW", "BV", "VB", "PF", "FP"
                Return 0.15
            Case Else
                Return 1.0
        End Select
    End Function
    Private Function costswapping_EN(ByVal chr1 As Char, ByVal chr2 As Char) As Decimal
        'cost of swapping two characters
        If IsVowel(chr1) And IsVowel(chr2) And IsValidVowelCombination(chr1, chr2) Then
            Return 0.15
        ElseIf (IsVowel(chr1) And Regex.IsMatch(chr2, "[BCDFGHJKLMNPQSTVWXYZ]") = True) Or (IsVowel(chr2) And Regex.IsMatch(chr1, "[BCDFGHJKLMNPQSTVWXYZ]") = True) Then
            Return 0.25
        ElseIf (IsVowel(chr1) And chr2 = "R") Or (IsVowel(chr2) And chr1 = "R") Then
            Return 0.15
        Else
            Return 0.35
        End If
    End Function
    Private Function IsVowel(ByVal chr As Char) As Boolean
        IsVowel = False
        If Regex.IsMatch(chr, "[AEIOU]") = True Then Return True
    End Function
    Private Function IsConsonant(ByVal chr As Char) As Boolean
        IsConsonant = False
        If Regex.IsMatch(chr, "[^AEIOU]") = True Then Return True
    End Function
    Private Function Min(ByVal values() As Decimal) As Object
        Dim i As Integer
        Dim min_value As Object
        min_value = values(LBound(values))
        For i = LBound(values) + 1 To UBound(values)
            If min_value > values(i) Then min_value = values(i)
        Next i
        Min = min_value
    End Function

End Class