import express from 'express'
import { readFileSync, writeFileSync, existsSync, unlinkSync, mkdirSync, readdirSync } from 'fs'
import { fileURLToPath } from 'url'
import { dirname, join } from 'path'
import crypto from 'crypto'
import multer from 'multer'

const __filename = fileURLToPath(import.meta.url)
const __dirname = dirname(__filename)

const app = express()
const PORT = process.env.PORT || 3090
const SERVER_VERSION = Date.now().toString()

const SCHEDULES_DIR = join(__dirname, 'schedules')
const SAVED_SCHEDULE_PATH = join(__dirname, 'saved_schedule.json')
const DEFAULT_DATA_PATH = join(__dirname, 'src', 'data.json')
// Multer config for Excel uploads
const upload = multer({
  dest: join(__dirname, 'uploads'),
  limits: { fileSize: 20 * 1024 * 1024 },
  fileFilter: (_req, file, cb) => {
    if (file.mimetype === 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' ||
        file.originalname.endsWith('.xlsx')) {
      cb(null, true)
    } else {
      cb(new Error('Only .xlsx files are accepted'))
    }
  }
})

app.use(express.json({ limit: '10mb' }))

// --- Helpers ---

function ensureSchedulesDir() {
  if (!existsSync(SCHEDULES_DIR)) {
    mkdirSync(SCHEDULES_DIR, { recursive: true })
  }
}

function listScheduleFiles() {
  ensureSchedulesDir()
  const files = readdirSync(SCHEDULES_DIR).filter(f => f.endsWith('.json'))
  const result = []
  for (const f of files) {
    try {
      const raw = JSON.parse(readFileSync(join(SCHEDULES_DIR, f), 'utf-8'))
      result.push({
        id: raw.id,
        name: raw.name,
        createdAt: raw.createdAt,
        modifiedAt: raw.modifiedAt,
      })
    } catch {}
  }
  result.sort((a, b) => new Date(b.modifiedAt) - new Date(a.modifiedAt))
  return result
}

function loadScheduleFile(id) {
  const filePath = join(SCHEDULES_DIR, `${id}.json`)
  if (!existsSync(filePath)) return null
  return JSON.parse(readFileSync(filePath, 'utf-8'))
}

function saveScheduleFile(fileObj) {
  ensureSchedulesDir()
  writeFileSync(join(SCHEDULES_DIR, `${fileObj.id}.json`), JSON.stringify(fileObj, null, 2), 'utf-8')
}

function getMostRecentFile() {
  const files = listScheduleFiles()
  return files.length > 0 ? files[0] : null
}

// --- Migration on startup ---

function migrateIfNeeded() {
  ensureSchedulesDir()
  const existing = readdirSync(SCHEDULES_DIR).filter(f => f.endsWith('.json'))
  if (existing.length === 0 && existsSync(SAVED_SCHEDULE_PATH)) {
    console.log('Migrating saved_schedule.json to schedules/ directory...')
    const data = JSON.parse(readFileSync(SAVED_SCHEDULE_PATH, 'utf-8'))
    const now = new Date().toISOString()
    const fileObj = {
      id: crypto.randomUUID(),
      name: `Migrated_Schedule_${now.slice(0, 10)}`,
      createdAt: now,
      modifiedAt: now,
      data,
    }
    saveScheduleFile(fileObj)
    console.log(`Migrated as ${fileObj.id} (${fileObj.name})`)
  }
}

migrateIfNeeded()

// --- Diff computation ---

function computeDiff(file1, file2) {
  const changes = []

  // Build lookup: personId -> { dayIdx -> value }
  function buildMap(data) {
    const map = {}
    if (!data) return map
    const people = data.people || data.stations
    if (!people) return map
    for (const person of people) {
      const cells = {}
      if (person.data) {
        for (const [idx, cellData] of Object.entries(person.data)) {
          if (cellData && cellData.v !== undefined && cellData.v !== null && cellData.v !== '') {
            cells[idx] = cellData.v
          }
        }
      }
      map[person.id || person.code] = cells
    }
    return map
  }

  const map1 = buildMap(file1.data)
  const map2 = buildMap(file2.data)

  // All person IDs from both files
  const allIds = new Set([...Object.keys(map1), ...Object.keys(map2)])

  for (const id of allIds) {
    const cells1 = map1[id] || {}
    const cells2 = map2[id] || {}
    const allIdx = new Set([...Object.keys(cells1), ...Object.keys(cells2)])

    for (const idx of allIdx) {
      const v1 = cells1[idx]
      const v2 = cells2[idx]
      const dayIdx = parseInt(idx)

      if (v1 !== undefined && v2 === undefined) {
        changes.push({ personId: id, dayIdx, type: 'removed', oldValue: v1 })
      } else if (v1 === undefined && v2 !== undefined) {
        changes.push({ personId: id, dayIdx, type: 'added', newValue: v2 })
      } else if (v1 !== v2) {
        changes.push({ personId: id, dayIdx, type: 'changed', oldValue: v1, newValue: v2 })
      }
    }
  }

  return { changes }
}

// --- API: File management ---

// List all files
app.get('/api/files', (_req, res) => {
  try {
    res.json(listScheduleFiles())
  } catch (err) {
    console.error('Error listing files:', err)
    res.status(500).json({ error: 'Failed to list files' })
  }
})

// Diff between two files
app.get('/api/files/diff/:id1/:id2', (req, res) => {
  try {
    const file1 = loadScheduleFile(req.params.id1)
    const file2 = loadScheduleFile(req.params.id2)
    if (!file1) return res.status(404).json({ error: `File ${req.params.id1} not found` })
    if (!file2) return res.status(404).json({ error: `File ${req.params.id2} not found` })
    res.json(computeDiff(file1, file2))
  } catch (err) {
    console.error('Error computing diff:', err)
    res.status(500).json({ error: 'Failed to compute diff' })
  }
})

// Import Excel (not yet implemented for TKB format)
app.post('/api/files/import-excel', upload.single('file'), (_req, res) => {
  res.status(501).json({ error: 'Excel import not yet implemented for TKB format' })
})

// Get single file
app.get('/api/files/:id', (req, res) => {
  try {
    const file = loadScheduleFile(req.params.id)
    if (!file) return res.status(404).json({ error: 'File not found' })
    res.json(file)
  } catch (err) {
    console.error('Error loading file:', err)
    res.status(500).json({ error: 'Failed to load file' })
  }
})

// Export file as Excel (not yet implemented for TKB format)
app.get('/api/files/:id/export-excel', (_req, res) => {
  res.status(501).json({ error: 'Excel export not yet implemented for TKB format' })
})

// Export docházka Excel for a given month
app.get('/api/files/:id/export-dochazka', async (req, res) => {
  const { id } = req.params
  const month = parseInt(req.query.month) || (new Date().getMonth() + 1)
  const year  = parseInt(req.query.year)  || new Date().getFullYear()

  const filePath = join(SCHEDULES_DIR, `${id}.json`)
  if (!existsSync(filePath)) return res.status(404).json({ error: 'File not found' })

  let fileData
  try { fileData = JSON.parse(readFileSync(filePath, 'utf8')) }
  catch { return res.status(500).json({ error: 'Failed to read file' }) }

  const input = JSON.stringify({ schedule: fileData.data, month, year })
  const scriptPath = join(__dirname, 'export_dochazka.py')

  try {
    const { spawn } = await import('child_process')
    await new Promise((resolve, reject) => {
      const chunks = []
      const errChunks = []
      const proc = spawn('python3', [scriptPath])
      proc.stdout.on('data', d => chunks.push(d))
      proc.stderr.on('data', d => errChunks.push(d))
      proc.on('close', code => {
        if (code !== 0) {
          const errMsg = Buffer.concat(errChunks).toString()
          console.error('export_dochazka error:', errMsg)
          reject(new Error(errMsg))
        } else {
          const xlsx = Buffer.concat(chunks)
          const MONTH_NAMES = ['','Leden','Únor','Březen','Duben','Květen','Červen','Červenec','Srpen','Září','Říjen','Listopad','Prosinec']
          const mm = String(month).padStart(2, '0')
          const fname = `OP2416101755_TKB_${year}_${mm}_${MONTH_NAMES[month]}.xlsx`
          res.setHeader('Content-Type', 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet')
          res.setHeader('Content-Disposition', `attachment; filename*=UTF-8''${encodeURIComponent(fname)}`)
          res.send(xlsx)
          resolve()
        }
      })
      proc.on('error', reject)
      proc.stdin.write(input)
      proc.stdin.end()
    })
  } catch (err) {
    if (!res.headersSent) res.status(500).json({ error: 'Export failed', details: err.message })
  }
})

// Create new file
app.post('/api/files', (req, res) => {
  try {
    const { name, data } = req.body
    if (!data || (!data.people && !data.stations) || !data.dayIndex) {
      return res.status(400).json({ error: 'Invalid schedule data (need people/stations and dayIndex)' })
    }
    const now = new Date().toISOString()
    const fileObj = {
      id: crypto.randomUUID(),
      name: name || `Schedule_${now.slice(0, 10)}`,
      createdAt: now,
      modifiedAt: now,
      data,
    }
    saveScheduleFile(fileObj)
    res.json({
      id: fileObj.id,
      name: fileObj.name,
      createdAt: fileObj.createdAt,
      modifiedAt: fileObj.modifiedAt,
    })
  } catch (err) {
    console.error('Error creating file:', err)
    res.status(500).json({ error: 'Failed to create file' })
  }
})

// Update existing file
app.put('/api/files/:id', (req, res) => {
  try {
    const file = loadScheduleFile(req.params.id)
    if (!file) return res.status(404).json({ error: 'File not found' })

    const { name, data } = req.body
    if (name !== undefined) file.name = name
    if (data) {
      if ((!data.people && !data.stations) || !data.dayIndex) {
        return res.status(400).json({ error: 'Invalid schedule data (need people/stations and dayIndex)' })
      }
      file.data = data
    }
    file.modifiedAt = new Date().toISOString()
    saveScheduleFile(file)

    res.json({
      id: file.id,
      name: file.name,
      createdAt: file.createdAt,
      modifiedAt: file.modifiedAt,
    })
  } catch (err) {
    console.error('Error updating file:', err)
    res.status(500).json({ error: 'Failed to update file' })
  }
})

// Delete file
app.delete('/api/files/:id', (req, res) => {
  try {
    const filePath = join(SCHEDULES_DIR, `${req.params.id}.json`)
    if (!existsSync(filePath)) return res.status(404).json({ error: 'File not found' })
    unlinkSync(filePath)
    res.json({ ok: true })
  } catch (err) {
    console.error('Error deleting file:', err)
    res.status(500).json({ error: 'Failed to delete file' })
  }
})

// --- Backward compatible endpoints ---

// GET /api/schedule — Load most recently modified file (or fallback to src/data.json)
app.get('/api/schedule', (_req, res) => {
  try {
    const recent = getMostRecentFile()
    if (recent) {
      const file = loadScheduleFile(recent.id)
      if (file) return res.json(file.data)
    }
    // Fallback to old paths
    if (existsSync(SAVED_SCHEDULE_PATH)) {
      return res.json(JSON.parse(readFileSync(SAVED_SCHEDULE_PATH, 'utf-8')))
    }
    res.json(JSON.parse(readFileSync(DEFAULT_DATA_PATH, 'utf-8')))
  } catch (err) {
    console.error('Error loading schedule:', err)
    res.status(500).json({ error: 'Failed to load schedule' })
  }
})

// POST /api/schedule — Save to most recently modified file (or create new one)
app.post('/api/schedule', (req, res) => {
  try {
    const data = req.body
    if (!data || (!data.people && !data.stations) || !data.dayIndex) {
      return res.status(400).json({ error: 'Invalid schedule data' })
    }

    const recent = getMostRecentFile()
    const now = new Date().toISOString()

    if (recent) {
      const file = loadScheduleFile(recent.id)
      if (file) {
        file.data = data
        file.modifiedAt = now
        saveScheduleFile(file)
        console.log(`Schedule saved to ${file.name} (${file.id}) at ${now}`)
        return res.json({ ok: true, id: file.id })
      }
    }

    // No existing file — create new
    const fileObj = {
      id: crypto.randomUUID(),
      name: `Schedule_${now.slice(0, 10)}`,
      createdAt: now,
      modifiedAt: now,
      data,
    }
    saveScheduleFile(fileObj)
    console.log(`Schedule saved as new file ${fileObj.name} (${fileObj.id}) at ${now}`)
    res.json({ ok: true, id: fileObj.id })
  } catch (err) {
    console.error('Error saving schedule:', err)
    res.status(500).json({ error: 'Failed to save schedule' })
  }
})

// --- API: Proposals ---

const PROPOSALS_PATH = join(__dirname, '..', 'proposals.md')

app.get('/api/proposals', (_req, res) => {
  try {
    if (existsSync(PROPOSALS_PATH)) {
      res.json({ content: readFileSync(PROPOSALS_PATH, 'utf-8') })
    } else {
      res.json({ content: '' })
    }
  } catch (err) {
    console.error('Error reading proposals:', err)
    res.status(500).json({ error: 'Failed to read proposals' })
  }
})

app.post('/api/proposals', (req, res) => {
  try {
    const { text, author } = req.body
    if (!text?.trim()) return res.status(400).json({ error: 'Empty proposal' })
    const now = new Date().toLocaleString('cs-CZ')
    const entry = `\n---\n\n**${now}** ${author ? `(${author})` : ''}\n\n${text.trim()}\n`

    let content = ''
    if (existsSync(PROPOSALS_PATH)) {
      content = readFileSync(PROPOSALS_PATH, 'utf-8')
    } else {
      content = '# Navrhy na vylepseni TKB Planu sluzeb\n'
    }
    content += entry
    writeFileSync(PROPOSALS_PATH, content, 'utf-8')
    res.json({ ok: true })
  } catch (err) {
    console.error('Error saving proposal:', err)
    res.status(500).json({ error: 'Failed to save proposal' })
  }
})

// API: export as Excel (legacy endpoint — not yet implemented for TKB format)
app.get('/api/export-excel', (_req, res) => {
  res.status(501).json({ error: 'Excel export not yet implemented for TKB format' })
})

// Version endpoint — clients poll this and reload when version changes
app.get('/api/version', (_req, res) => {
  res.json({ version: SERVER_VERSION })
})

// Serve static files from dist/
app.use(express.static(join(__dirname, 'dist'), {
  setHeaders: (res) => {
    res.setHeader('Cache-Control', 'no-cache, no-store, must-revalidate')
  }
}))

// SPA fallback
app.get('/{*splat}', (_req, res) => {
  res.sendFile(join(__dirname, 'dist', 'index.html'))
})

app.listen(PORT, () => {
  console.log(`TKB server running on http://localhost:${PORT}`)
})