import fs from 'node:fs'
import path from 'node:path'

import defaults from '../assets/codex-bridge/compression-defaults.json'

import type { CompressionSettings } from './compression-settings-types'

export function validateCompression(value: unknown): CompressionSettings {
  if (!value || typeof value !== 'object') throw new Error('Invalid compression settings')
  const v = value as CompressionSettings
  if (Object.keys(v).sort().join() !== Object.keys(defaults).sort().join()) throw new Error('Invalid settings fields')
  if (v.schemaVersion !== 1 || !['mini', 'az', 'orta', 'fazla', 'cok-fazla'].includes(v.level) || !['percent', 'tokens'].includes(v.budgetMode)) throw new Error('Invalid compression mode')
  for (const key of ['primaryModel', 'fallbackModel'] as const) {
    if (typeof v[key] !== 'string' || v[key].length > 256) throw new Error('Invalid model')
  }
  for (const key of ['autoEnabled', 'currentModelFallback'] as const) {
    if (typeof v[key] !== 'boolean') throw new Error('Invalid option')
  }
  const limits: [keyof CompressionSettings, number, number][] = [
    ['keepTurns', 1, 100], ['transferPercent', 10, 90], ['triggerPercent', 20, 90],
    ['targetPercent', 10, 80], ['maxTokens', 1024, 2000000], ['timeoutSeconds', 1, 3600]
  ]
  for (const [key, low, high] of limits) {
    const n = v[key]
    if (typeof n !== 'number' || !Number.isInteger(n) || n < low || n > high) throw new Error(`Invalid ${key}`)
  }
  if (v.targetPercent >= v.triggerPercent) throw new Error('Target must be below trigger')
  return structuredClone(v)
}

export function createCompressionStore(directory: string) {
  const file = path.join(directory, 'compression-settings.json')
  return {
    get: (): CompressionSettings => validateCompression(fs.existsSync(file) ? JSON.parse(fs.readFileSync(file, 'utf8')) : defaults),
    save(value: unknown): CompressionSettings {
      const next = validateCompression(value)
      fs.mkdirSync(directory, { recursive: true })
      const tmp = `${file}.${process.pid}.tmp`
      try {
        fs.writeFileSync(tmp, JSON.stringify(next, null, 2), { mode: 0o600 })
        fs.renameSync(tmp, file)
      } finally {
        if (fs.existsSync(tmp)) fs.unlinkSync(tmp)
      }
      return next
    }
  }
}