import React, { Component } from 'react';
import { Paper, Typography, Box, CircularProgress } from '@mui/material';
import { LineChart } from '@mui/x-charts/LineChart';

export default class Chart extends Component {
    constructor(props) {
        super(props);
        this.state = {
            data: [],
            loading: true
        };
        this.intervalId = null;
    }

    componentDidMount() {
        this.fetchData();
        this.intervalId = setInterval(this.fetchData, 60000);
    }

    componentDidUpdate(prevProps) {
        // Compare props to see if we need to refetch
        const prevEffective = this.getEffectiveChannels(prevProps);
        const currEffective = this.getEffectiveChannels(this.props);

        if (prevEffective.join(',') !== currEffective.join(',')) {
            this.fetchData();
        }
    }

    componentWillUnmount() {
        if (this.intervalId) {
            clearInterval(this.intervalId);
        }
    }

    getEffectiveChannels(props) {
        return props.channelConfig
            ? props.channelConfig.map(c => c.id)
            : props.selectedChannels;
    }

    fetchData = () => {
        const effectiveChannels = this.getEffectiveChannels(this.props);

        // Only fetch if selection exists
        if (effectiveChannels.length === 0) {
            this.setState({ data: [], loading: false });
            return;
        }

        const selectionStr = effectiveChannels.join(',');
        const since = new Date(Date.now() - 24 * 60 * 60 * 1000).toISOString();

        fetch(`/api/readings?selection=${encodeURIComponent(selectionStr)}&since=${since}`)
            .then(res => res.json())
            .then(rows => {
                const timeMap = new Map();

                rows.forEach(row => {
                    const id = `${row.device}:${row.channel}`;
                    if (!effectiveChannels.includes(id)) return;

                    const time = new Date(row.timestamp).getTime();
                    if (!timeMap.has(time)) {
                        timeMap.set(time, { time: new Date(row.timestamp) });
                    }
                    const entry = timeMap.get(time);

                    let val = row.value;
                    if (row.data_type === 'json' && !val) {
                        val = null;
                    }
                    entry[id] = val;
                });

                const sortedData = Array.from(timeMap.values()).sort((a, b) => a.time - b.time);
                this.setState({ data: sortedData, loading: false });
            })
            .catch(err => {
                console.error("Failed to fetch data", err);
                this.setState({ loading: false });
            });
    };

    computeAxisLimits(axisKey, effectiveChannels, series) {
        // Collect all data points for this axis
        let axisMin = Infinity;
        let axisMax = -Infinity;

        const axisSeries = series.filter(s => s.yAxisKey === axisKey).map(s => s.dataKey);

        if (axisSeries.length === 0) return {}; // No data for this axis

        // Check if config exists for this axis
        const { axisConfig } = this.props;
        let cfgMin = NaN;
        let cfgMax = NaN;
        if (axisConfig && axisConfig[axisKey]) {
            cfgMin = parseFloat(axisConfig[axisKey].min);
            cfgMax = parseFloat(axisConfig[axisKey].max);
        }

        // Optimization: If no config set, just return empty and let chart autoscale fully.
        if (isNaN(cfgMin) && isNaN(cfgMax)) return {};

        // Calculate data bounds
        let hasData = false;
        this.state.data.forEach(row => {
            axisSeries.forEach(key => {
                const val = row[key];
                if (val !== null && val !== undefined) {
                    hasData = true;
                    if (val < axisMin) axisMin = val;
                    if (val > axisMax) axisMax = val;
                }
            });
        });

        if (!hasData) return {}; // No valid data points

        // Apply config soft limits
        if (!isNaN(cfgMin)) axisMin = Math.min(axisMin, cfgMin);
        if (!isNaN(cfgMax)) axisMax = Math.max(axisMax, cfgMax);

        return { min: axisMin, max: axisMax };
    }

    render() {
        const { loading, data } = this.state;
        const { channelConfig } = this.props;
        const effectiveChannels = this.getEffectiveChannels(this.props);

        if (loading) return <Box sx={{ display: 'flex', justifyContent: 'center', p: 4 }}><CircularProgress /></Box>;
        if (effectiveChannels.length === 0) return <Box sx={{ p: 4 }}><Typography>No channels selected.</Typography></Box>;

        const series = effectiveChannels.map(id => {
            // Find alias and axis if config exists
            let label = id;
            let yAxisKey = 'left';
            if (channelConfig) {
                const item = channelConfig.find(c => c.id === id);
                if (item) {
                    if (item.alias) label = item.alias;
                    if (item.yAxis) yAxisKey = item.yAxis;
                }
            }

            return {
                dataKey: id,
                label: label,
                connectNulls: true,
                showMark: false,
                yAxisKey: yAxisKey,
            };
        });

        const hasRightAxis = series.some(s => s.yAxisKey === 'right');

        const leftLimits = this.computeAxisLimits('left', effectiveChannels, series);
        const rightLimits = this.computeAxisLimits('right', effectiveChannels, series);

        const yAxes = [
            { id: 'left', scaleType: 'linear', ...leftLimits }
        ];
        if (hasRightAxis) {
            yAxes.push({ id: 'right', scaleType: 'linear', ...rightLimits });
        }

        return (
            <Box sx={{ width: '100%', height: '80vh', p: 2 }}>
                <Typography variant="h6" gutterBottom>Last 24 Hours</Typography>
                <Paper sx={{ p: 2, height: '100%', display: 'flex', flexDirection: 'column' }}>
                    <Box sx={{ flexGrow: 1 }}>
                        <LineChart
                            dataset={data}
                            series={series}
                            xAxis={[{
                                dataKey: 'time',
                                scaleType: 'time',
                                valueFormatter: (date) => date.toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' })
                            }]}
                            yAxis={yAxes}
                            rightAxis={hasRightAxis ? 'right' : null}
                            slotProps={{
                                legend: {
                                    direction: 'row',
                                    position: { vertical: 'top', horizontal: 'middle' },
                                    padding: 0,
                                },
                            }}
                        />
                    </Box>
                </Paper>
            </Box>
        );
    }
}