import React, { useState, useRef } from 'react';
import { X, Upload, FileSpreadsheet, Loader, CheckCircle, AlertCircle, Trash2 } from 'lucide-react';

const API_BASE = process.env.REACT_APP_API_BASE || 'http://localhost:3001/api';
const PURPLE = '#A78BFA';

// ---------------------------------------------------------------------------
// Styles
// ---------------------------------------------------------------------------
const OVERLAY_STYLE = {
    position: 'fixed', inset: 0,
    background: 'rgba(0, 0, 0, 0.7)',
    backdropFilter: 'blur(4px)',
    zIndex: 100,
    display: 'flex', alignItems: 'center', justifyContent: 'center',
};

const MODAL_STYLE = {
    background: 'linear-gradient(180deg, #0F1A2E 0%, #0A1628 100%)',
    border: `1px solid ${PURPLE}40`,
    borderRadius: '1rem',
    width: '90%',
    maxWidth: '900px',
    maxHeight: '85vh',
    overflow: 'auto',
    padding: '2rem',
    boxShadow: `0 0 60px rgba(167, 139, 250, 0.15)`,
};

const DROP_ZONE_STYLE = {
    border: `2px dashed ${PURPLE}50`,
    borderRadius: '0.75rem',
    padding: '3rem 2rem',
    textAlign: 'center',
    cursor: 'pointer',
    transition: 'border-color 0.2s, background 0.2s',
};

const DROP_ZONE_ACTIVE = {
    ...DROP_ZONE_STYLE,
    borderColor: PURPLE,
    background: `${PURPLE}10`,
};

const FILE_ROW_STYLE = {
    display: 'flex',
    alignItems: 'center',
    gap: '1rem',
    padding: '0.75rem 1rem',
    borderRadius: '0.5rem',
    background: 'rgba(15, 23, 42, 0.6)',
    border: '1px solid rgba(255,255,255,0.06)',
    marginBottom: '0.5rem',
};

// phase: idle → uploading → preview → committing → done | error
export default function MultiVerticalUploadModal({ onClose, onUploadComplete }) {
    const [phase, setPhase] = useState('idle');
    const [files, setFiles] = useState([]);
    const [previewData, setPreviewData] = useState(null);
    const [error, setError] = useState(null);
    const [dragOver, setDragOver] = useState(false);
    const [commitResult, setCommitResult] = useState(null);
    const fileInputRef = useRef(null);

    // Handle file selection
    const handleFiles = (fileList) => {
        const newFiles = Array.from(fileList).filter(f => f.name.toLowerCase().endsWith('.xlsx'));
        if (newFiles.length === 0) {
            setError('Please select .xlsx files');
            return;
        }
        setFiles(prev => {
            const existing = new Set(prev.map(f => f.name));
            const unique = newFiles.filter(f => !existing.has(f.name));
            return [...prev, ...unique];
        });
        setError(null);
    };

    const removeFile = (index) => {
        setFiles(prev => prev.filter((_, i) => i !== index));
    };

    // Upload and preview
    const handlePreview = async () => {
        if (files.length === 0) return;
        setPhase('uploading');
        setError(null);

        const formData = new FormData();
        for (const file of files) {
            formData.append('files', file);
        }

        try {
            const res = await fetch(`${API_BASE}/compliance/vcl-multi/preview`, {
                method: 'POST',
                credentials: 'include',
                body: formData,
            });
            const data = await res.json();
            if (!res.ok) {
                setError(data.error || 'Upload failed');
                setPhase('idle');
                return;
            }
            setPreviewData(data);
            setPhase('preview');
        } catch (err) {
            setError('Network error: ' + err.message);
            setPhase('idle');
        }
    };

    // Commit
    const handleCommit = async () => {
        if (!previewData || !previewData.files || previewData.files.length === 0) return;
        setPhase('committing');
        setError(null);

        try {
            const res = await fetch(`${API_BASE}/compliance/vcl-multi/commit`, {
                method: 'POST',
                credentials: 'include',
                headers: { 'Content-Type': 'application/json' },
                body: JSON.stringify({
                    files: previewData.files.map(f => ({
                        tempFile: f.tempFile,
                        vertical: f.vertical,
                        report_date: f.report_date,
                        filename: f.filename,
                    })),
                }),
            });
            const data = await res.json();
            if (!res.ok) {
                setError(data.error || 'Commit failed');
                setPhase('preview');
                return;
            }
            setCommitResult(data);
            setPhase('done');
        } catch (err) {
            setError('Network error: ' + err.message);
            setPhase('preview');
        }
    };

    // Remove a file from preview
    const removePreviewFile = (index) => {
        setPreviewData(prev => ({
            ...prev,
            files: prev.files.filter((_, i) => i !== index),
        }));
    };

    return (
        <div style={OVERLAY_STYLE} onClick={onClose}>
            <div style={MODAL_STYLE} onClick={e => e.stopPropagation()}>
                {/* Header */}
                <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', marginBottom: '1.5rem' }}>
                    <h2 style={{ fontSize: '1.1rem', fontWeight: '700', color: '#E2E8F0', margin: 0 }}>
                        Upload Vertical Files
                    </h2>
                    <button onClick={onClose} style={{ background: 'none', border: 'none', color: '#64748B', cursor: 'pointer', padding: '0.25rem' }}>
                        <X style={{ width: '20px', height: '20px' }} />
                    </button>
                </div>

                {/* Phase: Idle — file selection */}
                {phase === 'idle' && (
                    <>
                        {/* Drop zone */}
                        <div
                            style={dragOver ? DROP_ZONE_ACTIVE : DROP_ZONE_STYLE}
                            onDragOver={e => { e.preventDefault(); setDragOver(true); }}
                            onDragLeave={() => setDragOver(false)}
                            onDrop={e => { e.preventDefault(); setDragOver(false); handleFiles(e.dataTransfer.files); }}
                            onClick={() => fileInputRef.current?.click()}
                        >
                            <Upload style={{ width: '32px', height: '32px', color: PURPLE, margin: '0 auto 0.75rem' }} />
                            <div style={{ fontSize: '0.85rem', color: '#E2E8F0', marginBottom: '0.25rem' }}>
                                Drop xlsx files here or click to browse
                            </div>
                            <div style={{ fontSize: '0.7rem', color: '#64748B' }}>
                                Expected format: VERTICAL_YYYY_MM_DD.xlsx (up to 14 files)
                            </div>
                        </div>
                        <input
                            ref={fileInputRef}
                            type="file"
                            accept=".xlsx"
                            multiple
                            style={{ display: 'none' }}
                            onChange={e => handleFiles(e.target.files)}
                        />

                        {/* Selected files list */}
                        {files.length > 0 && (
                            <div style={{ marginTop: '1.5rem' }}>
                                <div style={{ fontSize: '0.7rem', color: '#94A3B8', textTransform: 'uppercase', letterSpacing: '0.05em', marginBottom: '0.75rem' }}>
                                    Selected Files ({files.length})
                                </div>
                                {files.map((file, i) => (
                                    <div key={i} style={FILE_ROW_STYLE}>
                                        <FileSpreadsheet style={{ width: '16px', height: '16px', color: '#10B981', flexShrink: 0 }} />
                                        <span style={{ flex: 1, fontSize: '0.8rem', color: '#E2E8F0' }}>{file.name}</span>
                                        <span style={{ fontSize: '0.65rem', color: '#64748B' }}>{(file.size / 1024).toFixed(0)} KB</span>
                                        <button
                                            onClick={() => removeFile(i)}
                                            style={{ background: 'none', border: 'none', color: '#64748B', cursor: 'pointer', padding: '0.25rem' }}
                                            onMouseEnter={e => e.currentTarget.style.color = '#EF4444'}
                                            onMouseLeave={e => e.currentTarget.style.color = '#64748B'}
                                        >
                                            <Trash2 style={{ width: '14px', height: '14px' }} />
                                        </button>
                                    </div>
                                ))}

                                <button
                                    onClick={handlePreview}
                                    style={{
                                        marginTop: '1rem',
                                        padding: '0.7rem 2rem',
                                        background: PURPLE,
                                        border: 'none',
                                        borderRadius: '0.5rem',
                                        color: '#FFF',
                                        fontSize: '0.8rem',
                                        fontWeight: '600',
                                        cursor: 'pointer',
                                        width: '100%',
                                    }}
                                >
                                    Preview Upload
                                </button>
                            </div>
                        )}
                    </>
                )}

                {/* Phase: Uploading */}
                {phase === 'uploading' && (
                    <div style={{ textAlign: 'center', padding: '3rem' }}>
                        <Loader style={{ width: '32px', height: '32px', color: PURPLE, animation: 'spin 1s linear infinite', margin: '0 auto 1rem' }} />
                        <div style={{ fontSize: '0.85rem', color: '#E2E8F0' }}>Parsing {files.length} file(s)...</div>
                        <div style={{ fontSize: '0.7rem', color: '#64748B', marginTop: '0.25rem' }}>Extracting verticals and computing diffs</div>
                    </div>
                )}

                {/* Phase: Preview */}
                {phase === 'preview' && previewData && (
                    <>
                        <div style={{ fontSize: '0.7rem', color: '#94A3B8', textTransform: 'uppercase', letterSpacing: '0.05em', marginBottom: '1rem' }}>
                            Preview — {previewData.files.length} file(s) ready
                        </div>

                        {/* Preview table */}
                        <div style={{ overflowX: 'auto', marginBottom: '1rem' }}>
                            <table style={{ width: '100%', borderCollapse: 'collapse', fontSize: '0.75rem' }}>
                                <thead>
                                    <tr>
                                        <th style={{ padding: '0.5rem', textAlign: 'left', color: '#64748B', borderBottom: '1px solid rgba(255,255,255,0.08)' }}>Vertical</th>
                                        <th style={{ padding: '0.5rem', textAlign: 'left', color: '#64748B', borderBottom: '1px solid rgba(255,255,255,0.08)' }}>Date</th>
                                        <th style={{ padding: '0.5rem', textAlign: 'right', color: '#64748B', borderBottom: '1px solid rgba(255,255,255,0.08)' }}>Items</th>
                                        <th style={{ padding: '0.5rem', textAlign: 'right', color: '#10B981', borderBottom: '1px solid rgba(255,255,255,0.08)' }}>New</th>
                                        <th style={{ padding: '0.5rem', textAlign: 'right', color: '#F59E0B', borderBottom: '1px solid rgba(255,255,255,0.08)' }}>Recurring</th>
                                        <th style={{ padding: '0.5rem', textAlign: 'right', color: '#0EA5E9', borderBottom: '1px solid rgba(255,255,255,0.08)' }}>Resolved</th>
                                        <th style={{ padding: '0.5rem', textAlign: 'center', borderBottom: '1px solid rgba(255,255,255,0.08)' }}></th>
                                    </tr>
                                </thead>
                                <tbody>
                                    {previewData.files.map((f, i) => (
                                        <tr key={i}>
                                            <td style={{ padding: '0.5rem', color: PURPLE, fontWeight: '600' }}>{f.vertical}</td>
                                            <td style={{ padding: '0.5rem', color: '#94A3B8' }}>{f.report_date}</td>
                                            <td style={{ padding: '0.5rem', textAlign: 'right', color: '#E2E8F0' }}>{f.total_items}</td>
                                            <td style={{ padding: '0.5rem', textAlign: 'right', color: '#10B981' }}>{f.diff.new_count}</td>
                                            <td style={{ padding: '0.5rem', textAlign: 'right', color: '#F59E0B' }}>{f.diff.recurring_count}</td>
                                            <td style={{ padding: '0.5rem', textAlign: 'right', color: '#0EA5E9' }}>{f.diff.resolved_count}</td>
                                            <td style={{ padding: '0.5rem', textAlign: 'center' }}>
                                                {previewData.files.length > 1 && (
                                                    <button
                                                        onClick={() => removePreviewFile(i)}
                                                        style={{ background: 'none', border: 'none', color: '#64748B', cursor: 'pointer', padding: '0.2rem' }}
                                                        onMouseEnter={e => e.currentTarget.style.color = '#EF4444'}
                                                        onMouseLeave={e => e.currentTarget.style.color = '#64748B'}
                                                    >
                                                        <Trash2 style={{ width: '12px', height: '12px' }} />
                                                    </button>
                                                )}
                                            </td>
                                        </tr>
                                    ))}
                                </tbody>
                                <tfoot>
                                    <tr style={{ borderTop: '1px solid rgba(255,255,255,0.1)' }}>
                                        <td style={{ padding: '0.5rem', fontWeight: '600', color: '#E2E8F0' }}>Total</td>
                                        <td></td>
                                        <td style={{ padding: '0.5rem', textAlign: 'right', fontWeight: '600', color: '#E2E8F0' }}>
                                            {previewData.files.reduce((s, f) => s + f.total_items, 0)}
                                        </td>
                                        <td style={{ padding: '0.5rem', textAlign: 'right', fontWeight: '600', color: '#10B981' }}>
                                            {previewData.files.reduce((s, f) => s + f.diff.new_count, 0)}
                                        </td>
                                        <td style={{ padding: '0.5rem', textAlign: 'right', fontWeight: '600', color: '#F59E0B' }}>
                                            {previewData.files.reduce((s, f) => s + f.diff.recurring_count, 0)}
                                        </td>
                                        <td style={{ padding: '0.5rem', textAlign: 'right', fontWeight: '600', color: '#0EA5E9' }}>
                                            {previewData.files.reduce((s, f) => s + f.diff.resolved_count, 0)}
                                        </td>
                                        <td></td>
                                    </tr>
                                </tfoot>
                            </table>
                        </div>

                        {/* Unrecognized files */}
                        {previewData.unrecognized && previewData.unrecognized.length > 0 && (
                            <div style={{ marginBottom: '1rem', padding: '0.75rem', background: 'rgba(239, 68, 68, 0.1)', border: '1px solid rgba(239, 68, 68, 0.3)', borderRadius: '0.5rem' }}>
                                <div style={{ fontSize: '0.7rem', color: '#EF4444', fontWeight: '600', marginBottom: '0.5rem' }}>
                                    Unrecognized Files ({previewData.unrecognized.length})
                                </div>
                                {previewData.unrecognized.map((u, i) => (
                                    <div key={i} style={{ fontSize: '0.7rem', color: '#F87171', marginBottom: '0.25rem' }}>
                                        {u.filename}: {u.error}
                                    </div>
                                ))}
                            </div>
                        )}

                        {/* Actions */}
                        <div style={{ display: 'flex', gap: '1rem', marginTop: '1rem' }}>
                            <button
                                onClick={() => { setPhase('idle'); setPreviewData(null); }}
                                style={{
                                    flex: 1, padding: '0.7rem',
                                    background: 'transparent',
                                    border: '1px solid rgba(255,255,255,0.2)',
                                    borderRadius: '0.5rem',
                                    color: '#94A3B8',
                                    fontSize: '0.8rem',
                                    cursor: 'pointer',
                                }}
                            >
                                Back
                            </button>
                            <button
                                onClick={handleCommit}
                                disabled={previewData.files.length === 0}
                                style={{
                                    flex: 2, padding: '0.7rem',
                                    background: PURPLE,
                                    border: 'none',
                                    borderRadius: '0.5rem',
                                    color: '#FFF',
                                    fontSize: '0.8rem',
                                    fontWeight: '600',
                                    cursor: previewData.files.length === 0 ? 'not-allowed' : 'pointer',
                                    opacity: previewData.files.length === 0 ? 0.5 : 1,
                                }}
                            >
                                Commit {previewData.files.length} File(s)
                            </button>
                        </div>
                    </>
                )}

                {/* Phase: Committing */}
                {phase === 'committing' && (
                    <div style={{ textAlign: 'center', padding: '3rem' }}>
                        <Loader style={{ width: '32px', height: '32px', color: PURPLE, animation: 'spin 1s linear infinite', margin: '0 auto 1rem' }} />
                        <div style={{ fontSize: '0.85rem', color: '#E2E8F0' }}>Committing batch...</div>
                        <div style={{ fontSize: '0.7rem', color: '#64748B', marginTop: '0.25rem' }}>Writing to database with vertical-scoped resolution</div>
                    </div>
                )}

                {/* Phase: Done */}
                {phase === 'done' && commitResult && (
                    <div style={{ textAlign: 'center', padding: '2rem' }}>
                        <CheckCircle style={{ width: '48px', height: '48px', color: '#10B981', margin: '0 auto 1rem' }} />
                        <div style={{ fontSize: '1rem', color: '#E2E8F0', marginBottom: '0.5rem' }}>Upload Complete</div>
                        <div style={{ fontSize: '0.75rem', color: '#94A3B8', marginBottom: '1.5rem' }}>
                            {commitResult.committed.length} vertical(s) committed — {commitResult.total_new} new, {commitResult.total_resolved} resolved
                        </div>

                        {/* Per-vertical summary */}
                        <div style={{ textAlign: 'left', marginBottom: '1.5rem' }}>
                            {commitResult.committed.map((c, i) => (
                                <div key={i} style={{ ...FILE_ROW_STYLE, justifyContent: 'space-between' }}>
                                    <span style={{ color: PURPLE, fontWeight: '600', fontSize: '0.8rem' }}>{c.vertical}</span>
                                    <span style={{ fontSize: '0.7rem', color: '#64748B' }}>
                                        +{c.new_count} new / {c.recurring_count} recurring / -{c.resolved_count} resolved
                                    </span>
                                </div>
                            ))}
                        </div>

                        <button
                            onClick={() => { onUploadComplete(); }}
                            style={{
                                padding: '0.7rem 2rem',
                                background: PURPLE,
                                border: 'none',
                                borderRadius: '0.5rem',
                                color: '#FFF',
                                fontSize: '0.8rem',
                                fontWeight: '600',
                                cursor: 'pointer',
                            }}
                        >
                            Done
                        </button>
                    </div>
                )}

                {/* Error display */}
                {error && (
                    <div style={{ marginTop: '1rem', padding: '0.75rem', background: 'rgba(239, 68, 68, 0.1)', border: '1px solid rgba(239, 68, 68, 0.3)', borderRadius: '0.5rem', display: 'flex', alignItems: 'center', gap: '0.5rem' }}>
                        <AlertCircle style={{ width: '14px', height: '14px', color: '#EF4444', flexShrink: 0 }} />
                        <span style={{ fontSize: '0.75rem', color: '#F87171' }}>{error}</span>
                    </div>
                )}
            </div>
        </div>
    );
}