import { resolve, join } from 'path'
import { readFileSync, existsSync, statSync } from 'fs'
import yaml from 'js-yaml'
import { PROVIDER_PRESETS } from '../../shared/providers'
import { getDb } from '../../db'
import { MODEL_CONTEXT_TABLE } from '../../db/hermes/schemas'
import { detectHermesHome } from './hermes-path'

const HERMES_BASE = detectHermesHome()
const MODELS_DEV_CACHE = resolve(HERMES_BASE, 'models_dev_cache.json')
const DEFAULT_CONTEXT_LENGTH = 200_000

export interface ModelContextLengthOptions {
  profile?: string
  model?: string | null
  provider?: string | null
}

interface ModelLimit {
  context?: number
  output?: number
  input?: number
}

interface ModelEntry {
  id?: string
  name?: string
  limit?: ModelLimit
}

interface ProviderEntry {
  models?: Record<string, ModelEntry>
}

interface CustomProviderEntry {
  name?: string
  base_url?: string
  model?: string
  models?: Record<string, { context_length?: number }>
}

const MODEL_CACHE_PROVIDER_ALIASES: Record<string, string[]> = {
  gemini: ['google'],
  moonshot: ['moonshotai'],
  kilocode: ['kilo'],
  'ai-gateway': ['vercel'],
  'opencode-zen': ['opencode'],
  'opencode-go': ['opencode'],
  'glm-coding-plan': ['zai-coding-plan'],
  'kimi-coding': ['kimi-for-coding'],
  'kimi-coding-cn': ['kimi-for-coding'],
  'xai-oauth': ['xai'],
}

// --- Config YAML helpers (js-yaml) ---

function loadConfig(profileDir: string): any | null {
  const configPath = join(profileDir, 'config.yaml')
  if (!existsSync(configPath)) return null
  try {
    return yaml.load(readFileSync(configPath, 'utf-8'), { json: true }) as any
  } catch {
    return null
  }
}

// --- In-memory cache: parsed models_dev_cache (1.7MB), invalidated by mtime ---

let _cache: Record<string, ProviderEntry> | null = null
let _cacheMtime = 0
const CACHE_TTL_MS = 5 * 60 * 1000 // 5 minutes
let _cacheLoadedAt = 0

function loadModelsDevCache(): Record<string, ProviderEntry> | null {
  if (!existsSync(MODELS_DEV_CACHE)) return null
  try {
    const stat = statSync(MODELS_DEV_CACHE)
    const now = Date.now()
    // Return cached if file hasn't changed and within TTL
    if (_cache && stat.mtimeMs === _cacheMtime && now - _cacheLoadedAt < CACHE_TTL_MS) {
      return _cache
    }
    const raw = readFileSync(MODELS_DEV_CACHE, 'utf-8')
    _cache = JSON.parse(raw) as Record<string, ProviderEntry>
    _cacheMtime = stat.mtimeMs
    _cacheLoadedAt = now
    return _cache
  } catch {
    return _cache // return stale cache on error
  }
}

// --- Profile helpers ---

function getProfileDir(profile?: string): string {
  if (!profile || profile === 'default') return HERMES_BASE
  const dir = join(HERMES_BASE, 'profiles', profile)
  return existsSync(dir) ? dir : HERMES_BASE
}

function getDefaultModel(config: any): string | null {
  const model = config?.model
  if (!model || typeof model !== 'object') return null
  return typeof model.default === 'string' ? model.default.trim() || null : null
}

function getDefaultProvider(config: any): string | null {
  const model = config?.model
  if (!model || typeof model !== 'object') return null
  return typeof model.provider === 'string' ? model.provider.trim() || null : null
}

/**
 * Read context_length from config.yaml, only as a sibling of default.
 * e.g. model:\n  default: gpt-5.4\n  context_length: 200000
 */
function getConfigContextLength(config: any): number | null {
  const model = config?.model
  if (!model || typeof model !== 'object') return null
  const val = model.context_length
  if (typeof val !== 'number' || !Number.isFinite(val) || val <= 0) return null
  return val
}

function normalizeCustomProviderName(name: string): string {
  return name.trim().toLowerCase().replace(/ /g, '-')
}

function normalizeBaseUrl(url: string): string {
  return url.trim().toLowerCase().replace(/\/+$/, '')
}

function getModelBaseUrl(config: any): string | null {
  const model = config?.model
  if (!model || typeof model !== 'object') return null
  return typeof model.base_url === 'string' ? model.base_url.trim() || null : null
}

function getCustomProviders(config: any): CustomProviderEntry[] {
  return Array.isArray(config?.custom_providers) ? config.custom_providers as CustomProviderEntry[] : []
}

function resolveCustomProviderEntry(config: any, modelName: string, provider: string | null): CustomProviderEntry | null {
  if (!provider || !provider.startsWith('custom')) return null

  const providers = getCustomProviders(config)
  if (provider !== 'custom') {
    const suffix = normalizeCustomProviderName(provider.slice('custom:'.length))
    return providers.find((cp) => normalizeCustomProviderName(String(cp?.name || '')) === suffix) || null
  }

  const modelBaseUrl = getModelBaseUrl(config)
  if (modelBaseUrl) {
    const normalizedBaseUrl = normalizeBaseUrl(modelBaseUrl)
    const exactByBaseUrl = providers.find((cp) =>
      normalizeBaseUrl(String(cp?.base_url || '')) === normalizedBaseUrl
      && String(cp?.model || '').trim() === modelName,
    )
    if (exactByBaseUrl) return exactByBaseUrl
  }

  const matchesByModel = providers.filter((cp) => String(cp?.model || '').trim() === modelName)
  return matchesByModel.length === 1 ? matchesByModel[0] : null
}

/**
 * Lookup context_length from custom_providers in config.yaml.
 * - "custom:xxx" → strip prefix, match by name
 * - "custom" → match by model name
 */
function lookupCustomProviderContextLength(config: any, modelName: string, provider: string | null): number | null {
  const matched = resolveCustomProviderEntry(config, modelName, provider)
  if (!matched) return null

  const models = matched.models
  if (!models || typeof models !== 'object') return null

  const modelEntry = models[modelName]
  if (!modelEntry || typeof modelEntry !== 'object') return null

  const val = modelEntry.context_length
  if (typeof val !== 'number' || !Number.isFinite(val) || val <= 0) return null
  return val
}

// --- Context lookup ---

function getCachedContext(entry: ModelEntry | undefined): number | null {
  const context = entry?.limit?.context
  return typeof context === 'number' && Number.isFinite(context) && context > 0 ? context : null
}

function normalizeProviderKey(provider: string): string {
  return provider.trim().toLowerCase()
}

function getProviderCandidates(provider: string): string[] {
  const normalized = normalizeProviderKey(provider)
  return [normalized, ...(MODEL_CACHE_PROVIDER_ALIASES[normalized] || [])]
}

function getProviderEntry(data: Record<string, ProviderEntry>, provider: string): ProviderEntry | null {
  const candidates = getProviderCandidates(provider)

  for (const candidate of candidates) {
    const exact = data[candidate]
    if (exact) return exact
  }

  const entries = Object.entries(data)
  for (const candidate of candidates) {
    const match = entries.find(([name]) => name.toLowerCase() === candidate)
    if (match) return match[1]
  }

  return null
}

function findModelEntry(models: Record<string, ModelEntry>, modelName: string): ModelEntry | undefined {
  const exact = models[modelName]
  if (exact) return exact

  const lower = modelName.toLowerCase()
  for (const [name, entry] of Object.entries(models)) {
    if (name.toLowerCase() === lower) return entry
    if (entry.id?.toLowerCase() === lower) return entry
    if (entry.name?.toLowerCase() === lower) return entry
  }

  const suffix = `/${lower}`
  for (const [name, entry] of Object.entries(models)) {
    if (name.toLowerCase().endsWith(suffix)) return entry
    if (entry.id?.toLowerCase().endsWith(suffix)) return entry
  }

  return undefined
}

function lookupContextInProvider(provider: ProviderEntry | null, modelName: string): number | null {
  const models = provider?.models || {}
  return getCachedContext(findModelEntry(models, modelName))
}

function lookupContextGloballyByModelName(data: Record<string, ProviderEntry>, modelName: string): number | null {
  for (const prov of Object.values(data)) {
    const context = getCachedContext(prov.models?.[modelName])
    if (context) return context
  }

  const lower = modelName.toLowerCase()
  for (const prov of Object.values(data)) {
    const models = prov.models || {}
    for (const [name, entry] of Object.entries(models)) {
      if (name.toLowerCase() === lower) {
        const context = getCachedContext(entry)
        if (context) return context
      }
    }
  }

  return null
}

function lookupUniqueContextGloballyByModelName(data: Record<string, ProviderEntry>, modelName: string): number | null {
  const exactMatches: number[] = []
  for (const prov of Object.values(data)) {
    const context = getCachedContext(prov.models?.[modelName])
    if (context) exactMatches.push(context)
    if (exactMatches.length > 1) return null
  }
  if (exactMatches.length === 1) return exactMatches[0]

  const lower = modelName.toLowerCase()
  const ciMatches: number[] = []
  for (const prov of Object.values(data)) {
    const models = prov.models || {}
    for (const [name, entry] of Object.entries(models)) {
      if (name.toLowerCase() !== lower) continue
      const context = getCachedContext(entry)
      if (context) ciMatches.push(context)
      break
    }
    if (ciMatches.length > 1) return null
  }

  return ciMatches[0] || null
}

function resolveCacheProviderFromBaseUrl(baseUrl: string | null): string | null {
  if (!baseUrl) return null
  const normalizedBaseUrl = normalizeBaseUrl(baseUrl)
  const preset = PROVIDER_PRESETS.find((entry) => normalizeBaseUrl(entry.base_url) === normalizedBaseUrl)
  return preset?.value || null
}

function resolveCustomCacheProvider(config: any, modelName: string, provider: string): string | null {
  const customEntry = resolveCustomProviderEntry(config, modelName, provider)
  const entryBaseUrl = typeof customEntry?.base_url === 'string' ? customEntry.base_url : null
  const providerFromEntryBaseUrl = resolveCacheProviderFromBaseUrl(entryBaseUrl)
  if (providerFromEntryBaseUrl) return providerFromEntryBaseUrl

  return resolveCacheProviderFromBaseUrl(getModelBaseUrl(config))
}

function lookupContextFromCache(config: any, modelName: string, provider: string | null): number | null {
  const data = loadModelsDevCache()
  if (!data) return null

  if (provider) {
    if (provider === 'custom' || provider.startsWith('custom:')) {
      const inferredProvider = resolveCustomCacheProvider(config, modelName, provider)

      if (inferredProvider) {
        const scoped = lookupContextInProvider(getProviderEntry(data, inferredProvider), modelName)
        if (scoped) return scoped
        return null
      }

      if (provider === 'custom') {
        return lookupUniqueContextGloballyByModelName(data, modelName)
      }

      return null
    }

    return lookupContextInProvider(getProviderEntry(data, provider), modelName)
  }

  // Legacy configs may omit model.provider; preserve the old global exact/CI lookup semantics.
  return lookupContextGloballyByModelName(data, modelName)
}

/**
 * Get the context length for the current profile's default model.
 * Resolution order:
 *   1. config.yaml model.context_length (highest priority, user override)
 *   2. custom_providers models.<model>.context_length
 *   3. models_dev_cache.json, scoped to model.provider when configured
 *   4. DEFAULT_CONTEXT_LENGTH (200K hardcoded fallback)
 */
/**
 * 从数据库 model_context 表查找上下文长度（最高优先级）
 */
function lookupContextFromDatabase(modelName: string, provider: string | null): number | null {
  const db = getDb()
  if (!db) return null

  try {
    // 尝试精确匹配 provider 和 model
    const row = db
      .prepare(`SELECT context_limit FROM ${MODEL_CONTEXT_TABLE} WHERE provider = ? AND model = ?`)
      .get(provider || 'default', modelName) as { context_limit: number } | undefined

    return row?.context_limit || null
  } catch {
    return null
  }
}

export function getModelContextLength(input?: string | ModelContextLengthOptions): number {
  const options: ModelContextLengthOptions = typeof input === 'string'
    ? { profile: input }
    : input || {}
  const profile = options.profile
  const profileDir = getProfileDir(profile)
  const config = loadConfig(profileDir)
  if (!config) return DEFAULT_CONTEXT_LENGTH

  const model = String(options.model || '').trim() || getDefaultModel(config)
  if (!model) return DEFAULT_CONTEXT_LENGTH

  const provider = String(options.provider || '').trim() || getDefaultProvider(config)

  // 0. Database model_context table (highest priority)
  const dbCtx = lookupContextFromDatabase(model, provider)
  if (dbCtx && dbCtx > 0) return dbCtx

  // 1. Global context_length override in config.yaml
  const configCtx = getConfigContextLength(config)
  if (configCtx && configCtx > 0) return configCtx

  // 2. Custom provider context_length
  const customCtx = lookupCustomProviderContextLength(config, model, provider)
  if (customCtx && customCtx > 0) return customCtx

  // 3. models_dev_cache.json
  const cached = lookupContextFromCache(config, model, provider)
  if (cached) return cached

  // 4. Fallback
  return DEFAULT_CONTEXT_LENGTH
}