document.addEventListener('DOMContentLoaded', () => {
    const scenarioList = document.getElementById('scenario-list');
    const weatherSelect = document.getElementById('weather');
    const framesInput = document.getElementById('frames');
    const launchForm = document.getElementById('launch-form');
    const launchBtn = document.getElementById('launch-btn');
    const launchText = document.getElementById('launch-text');
    const launchSpinner = document.getElementById('launch-spinner');
    const terminalOutput = document.getElementById('terminal-output');
    const clearTerminalBtn = document.getElementById('clear-terminal');

    let currentEventSource = null;

    // Fetch Initial Config
    fetch('/api/config')
        .then(response => response.json())
        .then(config => {
            // Populate Scenarios
            config.scenarios.forEach((scenario, index) => {
                const isChecked = scenario === config.default_scenario ? 'checked' : '';
                const cardHtml = `
                    <label class="scenario-card">
                        <input type="radio" name="scenario" value="${scenario}" ${isChecked}>
                        <div class="card-content">
                            <span class="card-title">${scenario}</span>
                        </div>
                    </label>
                `;
                scenarioList.insertAdjacentHTML('beforeend', cardHtml);
            });

            // Listen for scenario changes to load dynamic parameters
            const scenarioRadios = document.querySelectorAll('input[name="scenario"]');
            scenarioRadios.forEach(radio => {
                radio.addEventListener('change', (e) => loadScenarioParams(e.target.value));
            });

            // Load params for the initially selected scenario
            if (config.default_scenario) {
                loadScenarioParams(config.default_scenario);
            }

            // Populate Weather
            config.weather_options.forEach(weather => {
                const isSelected = weather === config.default_weather ? 'selected' : '';
                const optionHtml = `<option value="${weather}" ${isSelected}>${weather}</option>`;
                weatherSelect.insertAdjacentHTML('beforeend', optionHtml);
            });

            // Default Frames
            framesInput.value = config.default_frames;
            
            appendLog(`> Config loaded successfully. Found ${config.scenarios.length} scenarios.`, 'system');
        })
        .catch(error => {
            appendLog(`> Error loading config: ${error.message}`, 'error');
        });

    // Handle Launch
    launchForm.addEventListener('submit', (e) => {
        e.preventDefault();
        
        // UI Loading State
        setLoadingState(true);
        appendLog(`\n> --- NEW SIMULATION RUN ---`, 'info');

        // Close existing stream if any
        if (currentEventSource) {
            currentEventSource.close();
        }

        const formData = new FormData(launchForm);
        
        // Scenario radions are in the sidebar, outside the form
        const scenarioRadio = document.querySelector('input[name="scenario"]:checked');
        const scenarioValue = scenarioRadio ? scenarioRadio.value : 'braking';

        // Serialize dynamic parameters
        const paramInputs = document.querySelectorAll('#dynamic-params-container input');
        let paramsString = [];
        paramInputs.forEach(input => {
            if (input.value !== '') {
                paramsString.push(`${input.name}=${input.value}`);
            }
        });

        const payload = {
            scenario: scenarioValue,
            frames: formData.get('frames'),
            weather: formData.get('weather'),
            no_record: formData.get('no_record') === 'on',
            params: paramsString.join(',')
        };

        // We use fetch API to trigger the run (which could take long), but Server Sent Events (SSE) 
        // doesn't support POST natively without fetch streams. So we do a POST fetch that returns an SSE stream.
        startStream('/api/run', payload);
    });

    // Clear Terminal
    clearTerminalBtn.addEventListener('click', () => {
        terminalOutput.innerHTML = '';
        appendLog('> Terminal cleared.', 'system');
    });

    // Utility: Append log to terminal
    function appendLog(text, type = '') {
        const line = document.createElement('div');
        line.className = `log-line ${type}`;
        
        // Simple heuristic for colored logs
        if (text.includes('[INFO]')) line.classList.add('info');
        if (text.includes('[WARN]')) line.classList.add('warn');
        if (text.includes('[ERROR]')) line.classList.add('error');
        if (text.includes('Traceback') || text.includes('Exception')) line.classList.add('error');

        line.textContent = text;
        terminalOutput.appendChild(line);
        terminalOutput.scrollTop = terminalOutput.scrollHeight;
    }

    // Utility: Post JSON and stream response
    async function startStream(url, payload) {
        try {
            const response = await fetch(url, {
                method: 'POST',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify(payload)
            });

            const reader = response.body.getReader();
            const decoder = new TextDecoder('utf-8');
            let buffer = '';

            while (true) {
                const { done, value } = await reader.read();
                if (done) break;

                buffer += decoder.decode(value, { stream: true });
                let boundary = buffer.indexOf('\n\n');
                
                while (boundary !== -1) {
                    const chunk = buffer.substring(0, boundary);
                    buffer = buffer.substring(boundary + 2);
                    
                    if (chunk.startsWith('data: ')) {
                        const data = chunk.substring(6);
                        
                        // Check for completion marker
                        if (data.startsWith('[PROCESS_COMPLETED]')) {
                            appendLog(`> Simulation Finished. ${data}`, 'info');
                            setLoadingState(false);
                        } else {
                            // Only append if it's not a carriage return override (like tqdm progress bars)
                            // We do a simple replacement to simulate carriage returns in HTML
                            if (data.includes('\r')) {
                                const parts = data.split('\r');
                                const lastPart = parts[parts.length - 1];
                                // Replace the content of the very last line if it exists
                                const lastLine = terminalOutput.lastElementChild;
                                if (lastLine && !lastLine.textContent.includes('\n')) {
                                    lastLine.textContent = lastPart;
                                    continue;
                                }
                            }
                            appendLog(data);
                        }
                    }
                    boundary = buffer.indexOf('\n\n');
                }
            }
        } catch (error) {
            appendLog(`> Connection error: ${error.message}`, 'error');
            setLoadingState(false);
        }
    }

    function setLoadingState(isLoading) {
        launchBtn.disabled = isLoading;
        launchText.style.display = isLoading ? 'none' : 'block';
        launchSpinner.style.display = isLoading ? 'block' : 'none';
        
        if (!isLoading) {
            launchText.textContent = "Launch Another Simulation";
        }
    }

    // Utility: Fetch and render dynamic scenario parameters
    function loadScenarioParams(scenarioName) {
        const container = document.getElementById('dynamic-params-container');
        container.innerHTML = '<div class="input-group full-width"><span class="helper">Loading parameters...</span></div>';

        fetch(`/api/scenario_params/${scenarioName}`)
            .then(res => res.json())
            .then(data => {
                container.innerHTML = '';
                if (data.success && Object.keys(data.params).length > 0) {
                    Object.entries(data.params).forEach(([key, val]) => {
                        const inputHtml = `
                            <div class="input-group">
                                <label for="param_${key}">${key}</label>
                                <div class="input-wrapper">
                                    <input type="text" id="param_${key}" name="${key}" value="${val}">
                                </div>
                            </div>
                        `;
                        container.insertAdjacentHTML('beforeend', inputHtml);
                    });
                } else {
                    container.innerHTML = '<div class="input-group full-width"><span class="helper">No tunable constants found for this scenario.</span></div>';
                }
            })
            .catch(err => {
                container.innerHTML = '<div class="input-group full-width"><span class="helper" style="color:var(--danger)">Failed to load parameters.</span></div>';
            });
    }
});