//
//  OmniIntent.swift
//  Zyquo Atlas
//
//  Author: Simon-Pierre Boucher
//  Mail: contact@spboucher.ai
//
//  Resolves omnibox input into a navigable URL: direct navigation vs. web
//  search. This is the Phase 2 URL-vs-search half of the smart omnibox; the
//  Phase 3 "ask AI" intent (docs/AI-BROWSER-RESEARCH.md §4.1) layers on top as a
//  third route with explicit affordances — deliberately not auto-hijacking
//  navigate/search here.
//

import Foundation

enum OmniIntent: Equatable {
    /// Navigate directly to this URL.
    case navigate(URL)
    /// Run a web search for this query.
    case search(String)

    /// The default search engine query template (`%@` replaced by the escaped query).
    static let searchTemplate = "https://duckduckgo.com/?q=%@"

    /// Classify raw omnibox text. Bias toward navigate/search (reversible,
    /// cheap) per the research; the AI "ask" route is opt-in elsewhere.
    static func resolve(_ raw: String) -> OmniIntent {
        let text = raw.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !text.isEmpty else { return .search("") }

        // Explicit scheme (http/https/file/about/data) → navigate.
        if let url = URL(string: text), let scheme = url.scheme?.lowercased(),
           ["http", "https", "file", "about", "data"].contains(scheme) {
            return .navigate(url)
        }

        // localhost / IP[:port] / bare host with a known-looking TLD and no
        // spaces → treat as a URL, defaulting to https.
        if !text.contains(" "), looksLikeHost(text) {
            if let url = URL(string: "https://\(text)") {
                return .navigate(url)
            }
        }

        return .search(text)
    }

    /// The URL to actually load for this intent.
    var url: URL? {
        switch self {
        case .navigate(let url):
            return url
        case .search(let query):
            let escaped = query.addingPercentEncoding(
                withAllowedCharacters: .urlQueryAllowed
            ) ?? query
            return URL(string: String(format: OmniIntent.searchTemplate, escaped))
        }
    }

    // MARK: - Heuristics

    private static func looksLikeHost(_ text: String) -> Bool {
        let host = text.split(separator: "/", maxSplits: 1).first.map(String.init) ?? text
        let bare = host.split(separator: ":", maxSplits: 1).first.map(String.init) ?? host
        if bare == "localhost" { return true }
        if isIPAddress(bare) { return true }
        // host.tld shape: at least one dot, a plausible TLD, no whitespace.
        guard let lastDot = bare.lastIndex(of: "."), lastDot != bare.startIndex else { return false }
        let tld = bare[bare.index(after: lastDot)...]
        return tld.count >= 2 && tld.allSatisfy { $0.isLetter }
    }

    private static func isIPAddress(_ s: String) -> Bool {
        let parts = s.split(separator: ".")
        guard parts.count == 4 else { return false }
        return parts.allSatisfy { part in
            guard let n = Int(part) else { return false }
            return (0...255).contains(n)
        }
    }
}