<# Merge curated defaults into the default VS Code profile settings. #>

[CmdletBinding()]
param()

$ErrorActionPreference = 'Stop'

function ConvertFrom-JsoncText {
    param([Parameter(Mandatory = $true)][string]$Text)

    $withoutComments = [System.Text.StringBuilder]::new()
    $state = 'Normal'
    $escaped = $false

    for ($i = 0; $i -lt $Text.Length; $i++) {
        $char = $Text[$i]
        $next = if ($i + 1 -lt $Text.Length) { $Text[$i + 1] } else { [char]0 }

        switch ($state) {
            'Normal' {
                if ($char -eq '"') {
                    [void]$withoutComments.Append($char)
                    $state = 'String'
                } elseif ($char -eq '/' -and $next -eq '/') {
                    $state = 'LineComment'
                    $i++
                } elseif ($char -eq '/' -and $next -eq '*') {
                    $state = 'BlockComment'
                    $i++
                } else {
                    [void]$withoutComments.Append($char)
                }
            }
            'String' {
                [void]$withoutComments.Append($char)
                if ($escaped) {
                    $escaped = $false
                } elseif ($char -eq '\') {
                    $escaped = $true
                } elseif ($char -eq '"') {
                    $state = 'Normal'
                }
            }
            'LineComment' {
                if ($char -eq "`r" -or $char -eq "`n") {
                    [void]$withoutComments.Append($char)
                    $state = 'Normal'
                }
            }
            'BlockComment' {
                if ($char -eq '*' -and $next -eq '/') {
                    $state = 'Normal'
                    $i++
                }
            }
        }
    }

    if ($state -eq 'BlockComment') {
        throw 'settings.json contains an unterminated block comment.'
    }

    $clean = $withoutComments.ToString()
    $withoutTrailingCommas = [System.Text.StringBuilder]::new()
    $state = 'Normal'
    $escaped = $false

    for ($i = 0; $i -lt $clean.Length; $i++) {
        $char = $clean[$i]
        if ($state -eq 'String') {
            [void]$withoutTrailingCommas.Append($char)
            if ($escaped) {
                $escaped = $false
            } elseif ($char -eq '\') {
                $escaped = $true
            } elseif ($char -eq '"') {
                $state = 'Normal'
            }
            continue
        }

        if ($char -eq '"') {
            [void]$withoutTrailingCommas.Append($char)
            $state = 'String'
            continue
        }

        if ($char -eq ',') {
            $lookAhead = $i + 1
            while ($lookAhead -lt $clean.Length -and [char]::IsWhiteSpace($clean[$lookAhead])) {
                $lookAhead++
            }
            if ($lookAhead -lt $clean.Length -and ($clean[$lookAhead] -eq '}' -or $clean[$lookAhead] -eq ']')) {
                continue
            }
        }
        [void]$withoutTrailingCommas.Append($char)
    }

    $json = $withoutTrailingCommas.ToString()
    if ([string]::IsNullOrWhiteSpace($json)) { $json = '{}' }
    return $json | ConvertFrom-Json
}

$settingsDir = if ($env:VSCODE_SETTINGS_DIR) {
    $env:VSCODE_SETTINGS_DIR
} else {
    Join-Path $env:APPDATA 'Code\User'
}
$settingsFile = Join-Path $settingsDir 'settings.json'
[void](New-Item -ItemType Directory -Path $settingsDir -Force)

$backupFile = $null
if (Test-Path -LiteralPath $settingsFile -PathType Leaf) {
    $timestamp = Get-Date -Format 'yyyyMMddHHmmssfff'
    $backupFile = "$settingsFile.backup.$timestamp"
    Copy-Item -LiteralPath $settingsFile -Destination $backupFile
    Write-Host "Backup created: $backupFile"
    $settings = ConvertFrom-JsoncText -Text ([System.IO.File]::ReadAllText($settingsFile))
    if ($settings -isnot [System.Management.Automation.PSCustomObject]) {
        throw 'settings.json must contain a JSON object.'
    }
} else {
    $settings = [pscustomobject]@{}
}

$managedSettings = [ordered]@{
    'editor.fontFamily'       = "'Ubuntu Mono', 'IBM Plex Mono', 'JetBrains Mono', Hack, MonoLisa, monospace"
    'editor.formatOnSave'     = $true
    'editor.lineHeight'       = 24
    'editor.renderWhitespace' = 'all'
    'editor.rulers'           = @(80, 100, 120)
    'editor.wordWrap'         = 'wordWrapColumn'
    'editor.wordWrapColumn'   = 80
    'workbench.colorTheme'    = 'GitHub Dark Default'
    'workbench.iconTheme'     = 'material-icon-theme'
}

foreach ($entry in $managedSettings.GetEnumerator()) {
    $settings | Add-Member -NotePropertyName $entry.Key -NotePropertyValue $entry.Value -Force
}

$tempFile = Join-Path $settingsDir ("settings.json.tmp.{0}" -f [guid]::NewGuid().ToString('N'))
try {
    $json = $settings | ConvertTo-Json -Depth 100
    [System.IO.File]::WriteAllText($tempFile, $json + [Environment]::NewLine, [System.Text.UTF8Encoding]::new($false))
    Move-Item -LiteralPath $tempFile -Destination $settingsFile -Force
} catch {
    Remove-Item -LiteralPath $tempFile -Force -ErrorAction SilentlyContinue
    if ($backupFile) { Write-Error "Could not merge settings. Original preserved at: $backupFile" }
    throw
}

Write-Host "VS Code settings updated: $settingsFile" -ForegroundColor Green