import Foundation

struct RDEPUBBuildDiagnosticsReporter {

    func phase7SemanticSummary(
        title: String?,
        diagnostics: [RDEPUBTextChapterPaginationDiagnostic]
    ) -> String? {

        guard !diagnostics.isEmpty else { return nil }

        let blockKinds = uniqueValues(from: diagnostics.flatMap(\.blockKinds))
        let semanticHints = uniqueValues(from: diagnostics.flatMap(\.semanticHints))
        let attachmentPlacements = uniqueValues(from: diagnostics.flatMap(\.attachmentPlacements))

        let note = diagnostics
            .flatMap(\.sampleNotes)
            .first(where: { $0.contains("semantic") || $0.contains("attachment") || $0.contains("block kinds") })

        var parts = [
            title,
            "章节 \(diagnostics.count)",
            blockKinds.isEmpty ? nil : "block kinds [\(blockKinds.map(\.rawValue).joined(separator: ","))]",
            semanticHints.isEmpty ? nil : "hints [\(semanticHints.map(\.rawValue).joined(separator: ","))]",
            attachmentPlacements.isEmpty ? nil : "placements [\(attachmentPlacements.map(\.rawValue).joined(separator: ","))]"
        ].compactMap { $0 }

        if let note {
            parts.append(note)
        }
        return parts.joined(separator: " · ")
    }

    func chapterDiagnostic(
        href: String,
        title: String,
        pages: [RDEPUBTextPage]
    ) -> RDEPUBTextChapterPaginationDiagnostic {
        RDEPUBTextChapterPaginationDiagnostic(
            href: href,
            title: title,
            pageCount: pages.count,
            breakReasons: pages.map(\.metadata.breakReason),

            attachmentPageCount: pages.filter { !$0.metadata.attachmentKinds.isEmpty }.count,

            blockAdjustedPageCount: pages.filter { $0.metadata.breakReason == .blockBoundary || $0.metadata.breakReason == .attachmentBoundary }.count,
            blockKinds: uniqueValues(from: pages.flatMap(\.metadata.blockKinds)),
            semanticHints: uniqueValues(from: pages.flatMap(\.metadata.semanticHints)),
            attachmentPlacements: uniqueValues(from: pages.flatMap(\.metadata.attachmentPlacements)),

            sampleNotes: Array(pages.flatMap(\.metadata.diagnostics).prefix(4))
        )
    }

    private func uniqueValues<T: Equatable>(from values: [T]) -> [T] {
        values.reduce(into: [T]()) { result, value in
            if !result.contains(value) {
                result.append(value)
            }
        }
    }
}