import Cocoa

var vars = [
    "AdobeCommon": "/Library/Application Support/Adobe",
    "df": "shouldn't get replaced",
    "durq": "wurqd!",
    "AdobeProgramFiles": "/Applications"
]

func parseVars(_ str: String) -> String {
    var out = str
    var substr = Substring(str)
    while let closeIndex = substr.lastIndex(of: "]") {
        substr = str[..<closeIndex]
        guard let openIndex = substr.lastIndex(of: "[") else {
            break
        }
        
        let name = String(str[str.index(openIndex, offsetBy: 1)..<closeIndex])
        if let value = vars[name] {
            out.replaceSubrange(openIndex...closeIndex, with: value)
        }
    }
    return out
}

let str = "asdfsdfkdj[AdobeCommon]][[df[]]testtt2][[durq]]"
print(str)
print(parseVars(str))
print(parseVars("[AdobeProgramFiles]/Adobe Photoshop 2020"))
// => asdfsdfkdj[AdobeCommon]][[df[]]testtt2][[durq]]
// => asdfsdfkdj/Library/Application Support/Adobe][[df[]]testtt2][wurqd!]
// => /Applications/Adobe Photoshop 2020