import Foundation

public enum RDEPUBNoteDetector {

    private static let noteTokens = [
        "noteref",      
        "footnote",     
        "endnote",      
        "rearnote",     
        "fnref",        
        "fn-",          
        "fn_",          
        "note",         
        "annotation"    
    ]

    public static func makeReferenceIfLikelyNote(
        sourceHref: String,
        sourceCFI: String?,
        targetHref: String,
        targetFragment: String?,
        targetCFI: String?,
        targetElementHTML: String?
    ) -> RDEPUBNoteReference? {

        let haystack = [
            targetHref,
            targetFragment ?? "",
            targetElementHTML ?? ""
        ].joined(separator: " ").lowercased()

        guard noteTokens.contains(where: { haystack.contains($0) }) ||
              hasEPUBType("footnote", in: targetElementHTML) ||
              hasEPUBType("endnote", in: targetElementHTML) ||
              hasEPUBType("rearnote", in: targetElementHTML) else {
            return nil
        }

        return RDEPUBNoteReference(
            sourceHref: sourceHref,
            sourceCFI: sourceCFI,
            targetHref: targetHref,
            targetFragment: targetFragment,
            targetCFI: targetCFI,
            label: targetFragment,
            kind: kind(from: haystack)
        )
    }

    public static func kind(from text: String) -> RDEPUBNoteKind {
        let lowered = text.lowercased()
        if lowered.contains("endnote") { return .endnote }
        if lowered.contains("rearnote") { return .rearnote }
        if lowered.contains("footnote") || lowered.contains("fn") { return .footnote }
        return .unknown
    }

    private static func hasEPUBType(_ type: String, in html: String?) -> Bool {
        guard let html else { return false }
        let pattern = #"epub:type\s*=\s*['"][^'"]*\b"# + NSRegularExpression.escapedPattern(for: type) + #"\b[^'"]*['"]"#
        return html.range(of: pattern, options: [.regularExpression, .caseInsensitive]) != nil
    }
}