import Foundation

/// Drives a finished session through the backend: chunk → sequential
/// `label-merge` (accumulating voiceprints) → assemble `speakers.json` → persist
/// fingerprints. Requests are sequential by construction (one chunk at a time).
final class TranscriptPipeline {
    private let client: SparkControlClient
    private let voiceprints: VoiceprintStore

    init(baseURL: String, skipTLS: Bool, voiceprints: VoiceprintStore) {
        self.client = SparkControlClient(baseURL: baseURL, skipTLS: skipTLS)
        self.voiceprints = voiceprints
    }

    /// Process a finished session. **Dual-channel** when the system track is healthy
    /// and present: mic (the local user) + system (remote) go as separate files, the
    /// `timeline` names only the remote speakers, and `selfSpans` become `self_vad`.
    /// Otherwise falls back to the **mono** mixed file with self folded into the
    /// timeline. Writes `speakers.json` into `sessionFolder`. `progress(done,total)`
    /// is called per chunk.
    func process(sessionFolder: URL,
                 sessionId: String,
                 app: String,
                 micURL: URL,
                 systemURL: URL,
                 mixedURL: URL,
                 timeline: [VisualTimeline.Segment],
                 selfSpans: [VADSpan],
                 selfName: String,
                 systemHealthy: Bool,
                 progress: ((Int, Int) async -> Void)? = nil) async throws -> SpeakersFile {
        let fm = FileManager.default
        let dual = systemHealthy
            && fm.fileExists(atPath: micURL.path) && fm.fileExists(atPath: systemURL.path)
            && SessionPackager.duration(of: systemURL) > 0
        let duration = dual
            ? max(SessionPackager.duration(of: micURL), SessionPackager.duration(of: systemURL))
            : SessionPackager.duration(of: mixedURL)
        let plan = SessionPackager.planChunks(durationSec: duration)

        // Zero-duration / empty session → a valid empty speakers.json, no backend call.
        if plan.isEmpty || duration <= 0 {
            let empty = TranscriptAssembler.assemble(sessionId: sessionId, app: app, chunks: [])
            try empty.speakersFile.write(to: sessionFolder.appendingPathComponent("speakers.json"))
            await progress?(0, 0)
            return empty.speakersFile
        }

        let chunksDir = sessionFolder.appendingPathComponent("chunks", isDirectory: true)
        try? fm.createDirectory(at: chunksDir, withIntermediateDirectories: true)
        defer { try? fm.removeItem(at: chunksDir) }   // cleanup on success OR throw

        // Start from stored voiceprints; accumulate this call's prints across chunks
        // for within-call unification (the store only persists high-confidence ones).
        var known = voiceprints.knownVoiceprints()
        var results: [TranscriptAssembler.ChunkResult] = []
        // Mono fallback needs self folded into the timeline; dual sends it separately.
        let monoTimeline = dual ? timeline
            : timeline + Self.timeline(fromSelfSpans: selfSpans, selfName: selfName)

        for chunk in plan {
            try Task.checkCancellation()
            await progress?(chunk.index, plan.count)
            let pad = String(format: "%03d", chunk.index)
            let response: LabelMergeResponse

            if dual {
                let micChunk = chunksDir.appendingPathComponent("chunk_\(pad)_mic.wav")
                let sysChunk = chunksDir.appendingPathComponent("chunk_\(pad)_sys.wav")
                try SessionPackager.sliceAudio(from: micURL, startSec: chunk.start, endSec: chunk.end, to: micChunk)
                try SessionPackager.sliceAudio(from: systemURL, startSec: chunk.start, endSec: chunk.end, to: sysChunk)
                guard fm.fileExists(atPath: micChunk.path), fm.fileExists(atPath: sysChunk.path) else { continue }
                let timelineData = try SessionPackager.rebasedTimelineData(timeline, start: chunk.start, end: chunk.end)
                let selfVadData = try SessionPackager.rebasedSelfVadData(selfSpans, start: chunk.start, end: chunk.end)
                response = try await client.labelMergeDual(
                    micURL: micChunk, systemURL: sysChunk, selfName: selfName, selfVad: selfVadData,
                    timeline: timelineData, knownVoiceprints: known.isEmpty ? nil : known, transcribe: true)
                try? fm.removeItem(at: micChunk); try? fm.removeItem(at: sysChunk)
            } else {
                let chunkURL = chunksDir.appendingPathComponent("chunk_\(pad).wav")
                try SessionPackager.sliceAudio(from: mixedURL, startSec: chunk.start, endSec: chunk.end, to: chunkURL)
                guard fm.fileExists(atPath: chunkURL.path) else { continue }   // empty slice → skip
                let timelineData = try SessionPackager.rebasedTimelineData(monoTimeline, start: chunk.start, end: chunk.end)
                response = try await client.labelMerge(
                    audioURL: chunkURL, timeline: timelineData,
                    knownVoiceprints: known.isEmpty ? nil : known, transcribe: true)
                try? fm.removeItem(at: chunkURL)
            }

            for (name, fp) in response.fingerprints where !LabelMergeResponse.isUnknownName(name) {
                known[name] = fp
            }
            voiceprints.update(with: response)
            results.append(.init(chunkStart: chunk.start, response: response,
                                 bodyStart: chunk.bodyStart, bodyEnd: chunk.bodyEnd))
        }
        await progress?(plan.count, plan.count)

        let assembled = TranscriptAssembler.assemble(sessionId: sessionId, app: app, chunks: results)
        try assembled.speakersFile.write(to: sessionFolder.appendingPathComponent("speakers.json"))
        // Persist every cluster's voiceprint (incl. Unknown) so the speaker editor can
        // teach the store a voice when the user renames an Unknown to a real name.
        if !assembled.allFingerprints.isEmpty,
           let data = try? JSONSerialization.data(withJSONObject: assembled.allFingerprints.mapValues { $0.map(Double.init) },
                                                  options: [.sortedKeys]) {
            try? data.write(to: sessionFolder.appendingPathComponent("cluster_fingerprints.json"))
        }
        return assembled.speakersFile
    }

    /// Build the `label-merge` timeline from mic-VAD self spans (Phase 1/2). Once
    /// the visual adapters land (Phase 3–4), their segments are merged in too.
    static func timeline(fromSelfSpans spans: [VADSpan], selfName: String) -> [VisualTimeline.Segment] {
        spans.map { .init(start: $0.start, end: $0.end, name: selfName, confidence: $0.confidence, source: "mic_vad") }
    }
}