export function initProgressPanel(ctx) {
    const sseUrl = '/api/telemetry/stream';
    let eventSource = null;

    function connect() {
        if (eventSource) return;

        eventSource = new EventSource(sseUrl);

        eventSource.onmessage = (event) => {
            try {
                const payload = JSON.parse(event.data);
                const { event: eventName, data } = payload;

                if (eventName === 'ingest_progress') {
                    handleIngestProgress(data);
                } else if (eventName === 'sae_progress') {
                    handleSaeProgress(data);
                }
            } catch (err) {
                console.error("Error parsing telemetry SSE event:", err);
            }
        };

        eventSource.onerror = (err) => {
            console.warn("SSE connection error, closing EventSource:", err);
            if (eventSource) {
                eventSource.close();
                eventSource = null;
            }
            // Auto reconnect after 3 seconds
            setTimeout(connect, 3000);
        };
    }

    function handleIngestProgress(data) {
        const container = document.getElementById('relief-ingest-progress');
        const phaseLabel = document.getElementById('relief-ingest-phase');
        const fillBar = document.getElementById('relief-ingest-fill');
        const subLabel = document.getElementById('relief-ingest-sublabel');
        const pctLabel = document.getElementById('relief-ingest-pct');
        const resultLabel = document.getElementById('relief-ingest-result');
        const shield = document.getElementById('relief-ingest-shield');

        if (!container) return;

        if (data.status === 'processing') {
            container.style.display = 'flex';
            container.classList.add('active');
            if (shield) shield.style.display = 'block';

            if (fillBar) fillBar.style.width = `${data.progress}%`;
            if (pctLabel) pctLabel.textContent = `${data.progress}%`;

            let stageMsg = "Processing...";
            if (data.stage === 'extract_text') {
                stageMsg = "Extracting text from PDF...";
                if (subLabel && data.current && data.total) {
                    subLabel.textContent = `Page ${data.current} / ${data.total}`;
                }
            } else if (data.stage === 'cleaning') {
                stageMsg = "Normalizing text...";
                if (subLabel) subLabel.textContent = "";
            } else if (data.stage === 'chunking') {
                stageMsg = "Splitting text into chunks...";
                if (subLabel) subLabel.textContent = "";
            } else if (data.stage === 'embeddings') {
                stageMsg = "Generating semantic embeddings...";
                if (subLabel && data.current && data.total) {
                    subLabel.textContent = `Chunk ${data.current} / ${data.total}`;
                }
            } else if (data.stage === 'storing') {
                stageMsg = "Storing in database...";
                if (subLabel) subLabel.textContent = "";
            }

            if (phaseLabel) phaseLabel.textContent = stageMsg;
            if (resultLabel) resultLabel.textContent = "";
        } else if (data.status === 'complete') {
            if (fillBar) fillBar.style.width = '100%';
            if (pctLabel) pctLabel.textContent = '100%';
            if (phaseLabel) phaseLabel.textContent = "Ingestion complete!";
            if (subLabel) subLabel.textContent = `${data.chunks} chunks generated`;

            if (resultLabel) {
                resultLabel.style.color = 'var(--color-semantic-success)';
                resultLabel.textContent = `✅ Successfully indexed ${data.chunks} chunks.`;
            }

            setTimeout(() => {
                if (shield) shield.style.display = 'none';
                container.style.display = 'none';
                container.classList.remove('active');
                if (resultLabel) resultLabel.textContent = "";
            }, 3000);

            // Reload file selector list!
            if (ctx && ctx.refresh && typeof ctx.refresh.reliefFiles === 'function') {
                ctx.refresh.reliefFiles(data.filename);
            }
        } else if (data.status === 'error') {
            if (phaseLabel) phaseLabel.textContent = "Error";
            if (resultLabel) {
                resultLabel.style.color = 'var(--color-semantic-error)';
                resultLabel.textContent = `❌ ${data.message || 'Unknown error'}`;
            }
            if (shield) shield.style.display = 'none';
            setTimeout(() => {
                container.style.display = 'none';
                container.classList.remove('active');
            }, 6000);
        }
    }

    function handleSaeProgress(data) {
        const progressContainer = document.getElementById('sae-training-progress');
        const fill = document.getElementById('sae-training-fill');
        const label = document.getElementById('sae-training-label');
        const saeStatusHint = document.getElementById('sae-status-hint');
        const saeToggle = document.getElementById('sae-space-toggle');
        const btnTrainSae = document.getElementById('btn-train-sae');

        if (!progressContainer) return;

        if (data.status === 'loading_vectors') {
            progressContainer.style.display = 'flex';
            if (fill) fill.style.width = '0%';
            if (label) label.textContent = "Loading vectors from database...";
            if (saeStatusHint) saeStatusHint.textContent = "Preparing data...";
            if (saeToggle) saeToggle.setAttribute('disabled', 'true');
            if (btnTrainSae) {
                btnTrainSae.setAttribute('disabled', 'true');
                btnTrainSae.textContent = '⏳ Preparing...';
            }
        } else if (data.status === 'training') {
            progressContainer.style.display = 'flex';
            if (fill) fill.style.width = `${data.progress}%`;
            if (label) {
                label.textContent = `Epoch ${data.current_epoch}/${data.total_epochs} (Loss: ${data.loss.toFixed(6)})`;
            }
            if (saeStatusHint) {
                saeStatusHint.textContent = "⏳ Training SAE on server...";
                saeStatusHint.style.color = 'var(--color-brand-secondary)';
            }
            if (btnTrainSae) {
                btnTrainSae.textContent = `⏳ Training (${data.progress}%)`;
                btnTrainSae.setAttribute('disabled', 'true');
            }
        } else if (data.status === 'success') {
            if (fill) fill.style.width = '100%';
            if (label) label.textContent = "Training complete.";
            setTimeout(() => {
                progressContainer.style.display = 'none';
            }, 3000);

            // Trigger saeStatus UI refresh
            if (ctx && ctx.refresh && typeof ctx.refresh.saeStatus === 'function') {
                ctx.refresh.saeStatus();
            }
        } else if (data.status === 'failed') {
            if (label) label.textContent = `Failed: ${data.error_message}`;
            if (saeStatusHint) {
                saeStatusHint.textContent = `❌ Failed: ${data.error_message}`;
                saeStatusHint.style.color = 'var(--color-semantic-error)';
            }
            setTimeout(() => {
                progressContainer.style.display = 'none';
            }, 5000);

            if (ctx && ctx.refresh && typeof ctx.refresh.saeStatus === 'function') {
                ctx.refresh.saeStatus();
            }
        }
    }

    connect();
}