import Foundation

/// Renders a per-host command template (an argv array from hosts.json) into a
/// single remote command string. Tokens are either literals or placeholders:
///   `{name}`  — required; substituted with `subs[name]` (empty if absent)
///   `{name?}` — optional; the whole word is dropped if the value is nil/empty
/// Every emitted word is single-quote-escaped, so titles/paths with spaces,
/// quotes, or `$` can never break out into shell syntax (argv-array semantics:
/// one array element → exactly one shell word).
public enum CommandTemplate {
    public static func render(_ template: [String], _ subs: [String: String?]) -> String {
        var words: [String] = []
        for token in template {
            if let ph = placeholder(token) {
                let value = subs[ph.name] ?? nil
                if ph.optional, value == nil || value!.isEmpty { continue }
                words.append(value ?? "")
            } else {
                words.append(token)
            }
        }
        return words.map(SSHTransport.shq).joined(separator: " ")
    }

    /// "{name}" → (name,false); "{name?}" → (name,true); otherwise nil (literal).
    static func placeholder(_ token: String) -> (name: String, optional: Bool)? {
        guard token.hasPrefix("{"), token.hasSuffix("}") else { return nil }
        var inner = String(token.dropFirst().dropLast())
        let optional = inner.hasSuffix("?")
        if optional { inner = String(inner.dropLast()) }
        guard !inner.isEmpty else { return nil }
        return (inner, optional)
    }
}