Handle malformed db entries (#87)

* Catch errors likely caused by null paths in db

The errors caused by reading the db when a location with no path set
has got into the database are actually `[InvalidCastException]`s thrown
when trying to convert the identifiers from the database into strings
for `[Location]`s.

This is caused by entries inserted with no path calling `GetById($null)`
so they get the 0-parameter version,
https://github.com/mbdavid/LiteDB/blob/f7ee275908ca48156a9d0bed054809955843e4b0/LiteDB/Document/BsonValue.cs#L49

Restricting the `catch{}` to `[IOException]` also means it's possible to
handle the file in use errors the retry logic is supposed to be
handling separately to other types of error.

* Move database retry logic inside catch block

Should result in more understandable error messages than using
`$Error[0]` and sometimes failing. Plus, will only trigger for
`IOException`s, which is what the file locked errors are reported
as.

* Check for and remove problem entries in db

If an `InvalidCastException` is encountered when running `DBFind`,
run a query to check for entries that look abnormal and remove them
from the database if found.

* Add mandatory params to ZLocation.psd1 exports

* Add mandatory params to ZLocation.Storage

* Add mandatory parameters to ZLocation.Service

`Add` and `Remove` could really use them, but can't add param blocks
to class methods.

* Add mandatory parameters to ZLocation.Search

* Add mandatory parameters for IsExactMatch

ZLocation/ZLocation.Search.psm1

@@ -2,8 +2,11 @@ Set-StrictMode -Version Latest
 
 if ((Get-Variable IsWindows -ErrorAction Ignore) -eq $null) { $IsWindows = $true }
 
-function Find-Matches([hashtable]$hash, [string[]]$query)
-{
+function Find-Matches {
+    param (
+        [Parameter(Mandatory=$true)] [hashtable]$hash, 
+        [string[]]$query
+    )
     $hash = $hash.Clone()
     foreach ($key in ($hash.GetEnumerator() | %{$_.Name}))
     {
@@ -39,18 +42,29 @@ function Find-Matches([hashtable]$hash, [string[]]$query)
     }
 }
 
-function Start-WithPrefix([string]$Path, [string]$lowerPrefix) {
+function Start-WithPrefix {
+    param (
+        [Parameter(Mandatory=$true)] [string]$Path, 
+        [Parameter(Mandatory=$true)] [string]$lowerPrefix
+    )
     $lowerLeaf = (Split-Path -Leaf $Path).ToLower()
     return $lowerLeaf.StartsWith($lowerPrefix)
 }
 
-function IsExactMatch([string]$Path, [string]$lowerPrefix) {
+function IsExactMatch {
+    param (
+        [Parameter(Mandatory=$true)] [string]$Path, 
+        [Parameter(Mandatory=$true)] [string]$lowerPrefix
+    )
     $lowerLeaf = (Split-Path -Leaf $Path).ToLower()
     return $lowerLeaf -eq $lowerPrefix
 }
 
-function Test-FuzzyMatch([string]$path, [string[]]$query)
-{
+function Test-FuzzyMatch {
+    param (
+        [Parameter(Mandatory=$true)] [string]$path,
+        [string[]]$query
+    )
     function contains([string]$left, [string]$right) {
         return [bool]($left.IndexOf($right, [System.StringComparison]::OrdinalIgnoreCase) -ge 0)
     }

ZLocation/ZLocation.Service.psm1

@@ -6,8 +6,27 @@ class Service {
     [Collections.Generic.IEnumerable[Location]] Get() {
         return (dboperation {
             # Return an enumerator of all location entries
-            [Location[]]$arr = DBFind $collection ([LiteDB.Query]::All()) ([Location])
-            ,$arr
+            try {
+                [Location[]]$arr = DBFind $collection ([LiteDB.Query]::All()) ([Location])
+                , $arr
+            }
+            catch [System.InvalidCastException] {
+                Write-Warning "Caught InvalidCastException when reading db, probably [LiteDB.ObjectId] entry present."
+                $oidquery = [LiteDB.Query]::Where('_id', {$args -like '{"$oid":"*"}'})
+                $problementries = (,$collection.Find($oidquery))
+                if ($problementries.Count -gt 0) {
+                    Write-Warning "Found $($problementries.Count) problem entries, attempting to remove..."
+                    $problementries | Write-Debug
+                    try {
+                        DBDelete $collection $oidquery | Out-Null
+                        Write-Warning 'Problem entries successfully removed, please repeat your command.'
+                    } catch {
+                        Write-Error 'Problem entries could not be removed.'
+                    }
+                } else {
+                        Write-Error 'No problem entries found, please open an issue on https://github.com/vors/ZLocation'
+                }
+            }
         })
     }
     [void] Add([string]$path, [double]$weight) {
@@ -57,7 +76,10 @@ function Get-ZLocationLegacyBackupFilePath
  See: https://github.com/mbdavid/LiteDB/wiki/Concurrency
  Exposes $db and $collection variables for use by the $scriptblock
 #>
-function dboperation($private:scriptblock) {
+function dboperation {
+    param (
+        [Parameter(Mandatory=$true)] $private:scriptblock
+    )
     $Private:Mode = if (Get-Variable IsMacOS -ErrorAction Ignore) { 'Exclusive' } else { 'Shared' }
     # $db and $collection will be in-scope within $scriptblock
     $db = DBOpen "Filename=$( Get-ZLocationDatabaseFilePath ); Mode=$Mode"
@@ -68,13 +90,16 @@ function dboperation($private:scriptblock) {
             try {
                 & $private:scriptblock
                 return
-            } catch {
-                $rand = Get-Random 100
-                Start-Sleep -Milliseconds (($__i + 1) * 100 - $rand)
+            } catch [System.IO.IOException] {
+                # The process cannot access the file '~\z-location.db' because it is being used by another process.
+                if ($__i -lt 4 ) {
+                    $rand = Get-Random 100
+                    Start-Sleep -Milliseconds (($__i + 1) * 100 - $rand)
+                } else {
+                    throw [System.IO.IOException] 'Cannot execute database operation after 5 attempts, please open an issue on https://github.com/vors/ZLocation'
+                }
             }
         }
-        Write-Error $error[0]
-        throw 'Cannot execute database operation after 5 attempts, please open an issue on https://github.com/vors/ZLocation'
     } finally {
         $db.dispose()
     }

ZLocation/ZLocation.Storage.psm1

@@ -23,12 +23,19 @@ function Get-ZLocation($Match)
     return $hash
 }
 
-function Add-ZWeight([string]$path, [double]$weight) {
+function Add-ZWeight {
+    param (
+        [Parameter(Mandatory=$true)] [string]$Path,
+        [Parameter(Mandatory=$true)] [double]$Weight
+    )
     $service = Get-ZService
     $service.Add($path, $weight)
 }
 
-function Remove-ZLocation([string]$path) {
+function Remove-ZLocation {
+    param (
+        [Parameter(Mandatory=$true)] [string]$Path
+    )
     $service = Get-ZService
     $service.Remove($path)
 }

ZLocation/ZLocation.psm1

@@ -37,8 +37,11 @@ function Update-ZLocation([string]$path)
 (Get-Variable pwd).attributes.Add((new-object ValidateScript { Update-ZLocation $_.Path; return $true }))
 #>
 
-function Update-ZLocation([string]$path)
+function Update-ZLocation
 {
+    param (
+        [Parameter(Mandatory=$true)] [string]$Path
+    )
     Add-ZWeight $path 1.0
 }