import Foundation

/// Reconciles the backend's per-cluster speaker labels into cleaner identities:
/// 1. **Merge** non-self clusters whose voiceprints are highly similar — fixes one
///    person being split across chunks (e.g. "MH" + "Unknown_0" → one person).
/// 2. **Name** remaining non-self clusters from the transcript *content* (people
///    addressed by name, self-introductions) via the gateway LLM — fixes wrong/initial
///    labels that the visual cue produced. Conservative: keeps the current label when
///    the content doesn't clearly reveal a name; never touches the mic-channel self.
///
/// The merge math is pure/testable; the naming pass is one LLM call.
enum SpeakerReconciler {

    /// Full reconciliation: merge by voiceprint → dissolve fragment clusters → name
    /// remaining non-self clusters by content (guard-railed).
    static func reconcile(file: SpeakersFile, fingerprints: [String: [Float]], selfName: String,
                          llm: GatewayLLMClient, model: String,
                          mergeThreshold: Double = 0.82) async -> SpeakersFile {
        let protected = protectedNames(file, selfName: selfName)
        let merged = mergeByFingerprint(file, fingerprints: fingerprints, protected: protected, threshold: mergeThreshold)
        let smoothed = smoothFragments(merged, protected: protected)

        // Name the non-self clusters from content.
        let labels = SpeakerEditing.orderedSpeakers(smoothed.segments).filter { !protected.contains($0) }
        guard !labels.isEmpty else { return smoothed }
        // Names the LLM must NOT reuse for another speaker: self + everyone already named.
        let forbidden = protected.union(labels.filter { !LabelMergeResponse.isUnknownName($0) })
        let prompt = namingPrompt(file: smoothed, selfName: selfName, labels: labels, forbidden: forbidden)
        guard let content = try? await llm.completeJSON(model: model, system: nil, user: prompt, maxTokens: 1024) else {
            return smoothed
        }
        let names = parseNaming(content)
        var renamed = smoothed
        var used = Set(SpeakerEditing.orderedSpeakers(smoothed.segments))
        for (current, proposal) in names where current != proposal.name {
            let new = proposal.name
            guard !new.isEmpty, proposal.confidence != "low",
                  !protected.contains(current), !LabelMergeResponse.isUnknownName(new),
                  !protected.contains(new),            // never assign the self/protected name to another voice
                  !(used.contains(new) && new != current)   // never collide with an already-present different speaker
            else { continue }
            renamed = apply(rename: current, to: new, source: "content", in: renamed)
            used.remove(current); used.insert(new)
        }
        return renamed
    }

    /// Dissolve fragment clusters: a non-self "speaker" whose segments are MOSTLY tiny
    /// (median duration ≤ `shortDur`) isn't a real participant — it's diarization
    /// micro-fragments (single words split off mid-sentence; one stray longer segment
    /// shouldn't rescue it, so we use the median, not the max). Reassign each of its
    /// segments to the temporally-nearest real speaker. Pure/testable.
    static func smoothFragments(_ file: SpeakersFile, protected: Set<String>,
                                shortDur: Double = 1.0, minSegs: Int = 3) -> SpeakersFile {
        var durs: [String: [Double]] = [:]
        for s in file.segments { durs[s.speaker, default: []].append(s.end - s.start) }
        func isReal(_ name: String) -> Bool {
            if protected.contains(name) { return true }
            guard let d = durs[name], d.count >= minSegs else { return true }   // too few to judge → keep
            let sorted = d.sorted()
            return sorted[sorted.count / 2] > shortDur                          // median > shortDur → real
        }
        guard file.segments.contains(where: { isReal($0.speaker) }),
              file.segments.contains(where: { !isReal($0.speaker) }) else { return file }

        let out = file.segments.sorted { $0.start < $1.start }
        var result = out
        for i in out.indices where !isReal(out[i].speaker) {
            var bestName: String?, bestGap = Double.greatestFiniteMagnitude
            var j = i - 1
            while j >= 0 { if isReal(out[j].speaker) { let gap = out[i].start - out[j].end; if gap < bestGap { bestGap = gap; bestName = out[j].speaker }; break }; j -= 1 }
            var k = i + 1
            while k < out.count { if isReal(out[k].speaker) { let gap = out[k].start - out[i].end; if gap < bestGap { bestGap = gap; bestName = out[k].speaker }; break }; k += 1 }
            if let name = bestName {
                let s = out[i]
                result[i] = SpeakersFile.Segment(start: s.start, end: s.end, speaker: name, text: s.text)
            }
        }
        let keep = SpeakerEditing.orderedSpeakers(result)
        let speakers = keep.map { n in file.speakers.first { $0.name == n } ?? SpeakersFile.Speaker(name: n, source: "reconciled", overlapConfidence: nil, matchSimilarity: nil) }
        return SpeakersFile(sessionId: file.sessionId, app: file.app, durationSec: file.durationSec,
                            speakers: speakers, segments: result, models: file.models)
    }

    // MARK: - Voiceprint merge (pure)

    static func protectedNames(_ file: SpeakersFile, selfName: String) -> Set<String> {
        var p: Set<String> = [selfName]
        for s in file.speakers where s.source == "mic_channel" { p.insert(s.name) }
        return p
    }

    static func cosine(_ a: [Float], _ b: [Float]) -> Double {
        guard a.count == b.count, !a.isEmpty else { return 0 }
        var dot = 0.0, na = 0.0, nb = 0.0
        for i in 0..<a.count { dot += Double(a[i] * b[i]); na += Double(a[i] * a[i]); nb += Double(b[i] * b[i]) }
        guard na > 0, nb > 0 else { return 0 }
        return dot / (na.squareRoot() * nb.squareRoot())
    }

    /// Greedily merge non-self clusters with cosine similarity ≥ threshold. The
    /// survivor is the "better-named" one (a real name beats Unknown; higher
    /// confidence wins ties). Segments + the speaker roster are remapped.
    static func mergeByFingerprint(_ file: SpeakersFile, fingerprints: [String: [Float]],
                                   protected: Set<String>, threshold: Double) -> SpeakersFile {
        let names = file.speakers.map { $0.name }.filter { !protected.contains($0) && fingerprints[$0] != nil }
        guard names.count > 1 else { return file }
        let rank = Dictionary(uniqueKeysWithValues: file.speakers.map { ($0.name, $0) })

        var canonical: [String: String] = [:]   // name -> survivor
        for n in names { canonical[n] = n }
        func find(_ x: String) -> String { var r = x; while canonical[r]! != r { r = canonical[r]! }; return r }

        for i in 0..<names.count {
            for j in (i + 1)..<names.count {
                let a = find(names[i]), b = find(names[j])
                guard a != b, let fa = fingerprints[a], let fb = fingerprints[b] else { continue }
                if cosine(fa, fb) >= threshold {
                    let survivor = better(a, b, rank: rank)
                    let absorbed = survivor == a ? b : a
                    canonical[absorbed] = survivor
                }
            }
        }
        let map = Dictionary(uniqueKeysWithValues: names.map { ($0, find($0)) }).filter { $0.key != $0.value }
        guard !map.isEmpty else { return file }

        let segments = file.segments.map { s in map[s.speaker].map {
            SpeakersFile.Segment(start: s.start, end: s.end, speaker: $0, text: s.text) } ?? s }
        let keep = SpeakerEditing.orderedSpeakers(segments)
        let speakers = keep.map { rank[$0] ?? SpeakersFile.Speaker(name: $0, source: "reconciled", overlapConfidence: nil, matchSimilarity: nil) }
        return SpeakersFile(sessionId: file.sessionId, app: file.app, durationSec: file.durationSec,
                            speakers: speakers, segments: segments, models: file.models)
    }

    /// Prefer a real name over Unknown; otherwise the higher-confidence cluster.
    private static func better(_ a: String, _ b: String, rank: [String: SpeakersFile.Speaker]) -> String {
        let au = LabelMergeResponse.isUnknownName(a), bu = LabelMergeResponse.isUnknownName(b)
        if au != bu { return au ? b : a }
        let ca = (rank[a]?.overlapConfidence ?? rank[a]?.matchSimilarity ?? 0)
        let cb = (rank[b]?.overlapConfidence ?? rank[b]?.matchSimilarity ?? 0)
        return ca >= cb ? a : b
    }

    private static func apply(rename current: String, to new: String, source: String, in file: SpeakersFile) -> SpeakersFile {
        let segments = SpeakerEditing.replaceSpeaker(current, with: new, in: file.segments)
        let speakers = SpeakerEditing.orderedSpeakers(segments).map { name -> SpeakersFile.Speaker in
            if name == new { return SpeakersFile.Speaker(name: new, source: source, overlapConfidence: nil, matchSimilarity: nil) }
            return file.speakers.first { $0.name == name } ?? SpeakersFile.Speaker(name: name, source: "reconciled", overlapConfidence: nil, matchSimilarity: nil)
        }
        return SpeakersFile(sessionId: file.sessionId, app: file.app, durationSec: file.durationSec,
                            speakers: speakers, segments: segments, models: file.models)
    }

    // MARK: - LLM content naming

    static func namingPrompt(file: SpeakersFile, selfName: String, labels: [String], forbidden: Set<String>) -> String {
        let entries = RecapAnalyzer.entries(from: file)
        let transcript = RecapAnalyzer.cappedTranscript(entries, maxChars: 20_000)
        let forbiddenList = forbidden.sorted().joined(separator: ", ")
        return """
        You are reconciling speaker labels in a diarized transcript. The voices were separated acoustically and labeled with placeholder initials or "Unknown_N". Your ONLY job is to map a placeholder to a person's REAL name when the conversation UNAMBIGUOUSLY reveals it — they introduce themselves ("this is Sarah"), or are directly addressed AND respond. Hearing a name mentioned is NOT enough; people are talked ABOUT without being on the call. When in doubt, return null. Precision matters far more than coverage — a wrong name is worse than no name.

        "\(selfName)" is the local user (their own channel) and is already correct.
        Do NOT assign any of these already-taken names to a different speaker: \(forbiddenList)
        Each real name may be used for AT MOST ONE label.

        LABELS TO RESOLVE: \(labels.joined(separator: ", "))

        TRANSCRIPT (each line is "[<label> <MM:SS>] text"):
        \(transcript)

        Respond with ONLY valid JSON, no other text. Use "high" confidence only when a label introduced themselves or was directly addressed and answered:
        {
          "speakers": [
            {"current": "<label>", "name": "Real Name" or null, "confidence": "high" | "medium" | "low"}
          ]
        }
        """
    }

    static func parseNaming(_ content: String) -> [String: (name: String, confidence: String)] {
        let cleaned = GatewayLLMClient.stripCodeFence(content)
        guard let o = (try? JSONSerialization.jsonObject(with: Data(cleaned.utf8))) as? [String: Any],
              let arr = o["speakers"] as? [[String: Any]] else { return [:] }
        var out: [String: (name: String, confidence: String)] = [:]
        for d in arr {
            guard let cur = (d["current"] as? String)?.trimmingCharacters(in: .whitespacesAndNewlines), !cur.isEmpty,
                  let name = (d["name"] as? String)?.trimmingCharacters(in: .whitespacesAndNewlines),
                  !name.isEmpty, name.lowercased() != "null" else { continue }
            let conf = (d["confidence"] as? String)?.lowercased() ?? "medium"
            out[cur] = (name, conf)
        }
        return out
    }
}