import fs from 'node:fs/promises'
import path from 'node:path'
import { load } from 'js-yaml'
import { and, eq, inArray } from 'drizzle-orm'
import { parseModuleProps } from '../helpers/common.ts'
import { sites as sitesTable, storage as storageTable } from '../db/schema.ts'
import type { ModuleProp } from '../helpers/common.ts'

/** The kinds of content a target can be asked to hold. */
export const CONTENT_TYPES = ['pages', 'images', 'documents', 'others', 'large'] as const

/**
 * The module every site stores its content in, and the only one that is guaranteed to work: assets
 * and pages live in the wiki database. It cannot be disabled, as that would leave content nowhere.
 */
const DB_MODULE = 'db'

/** An action a module knows how to run on demand, as declared by its `definition.yml`. */
export interface StorageAction {
  /** Key of the handler on the module implementation, i.e. what gets called. */
  handler: string
  label: string
  hint: string
  /** Shown in red, and turned into a confirmation prompt by the admin area. */
  warn?: string
  icon: string
}

/** A storage module, as declared by its `definition.yml`. */
export interface StorageDefinition {
  key: string
  title: string
  description: string
  icon: string
  banner: string
  vendor: string
  website: string
  contentTypes: {
    defaultTypesEnabled: string[]
    defaultLargeThreshold: string
  }
  assetDelivery: {
    isStreamingSupported: boolean
    isDirectAccessSupported: boolean
    defaultStreamingEnabled: boolean
    defaultDirectAccessEnabled: boolean
  }
  versioning: {
    isSupported: boolean
    /** Versioning is inherent to the module and cannot be turned off, as in a git history. */
    isForceEnabled: boolean
    defaultEnabled: boolean
  }
  /** Declared by modules that cannot be configured by hand, e.g. an app installed on a provider. */
  setup?: {
    handler: string
    defaultValues: Record<string, any>
  }
  props: Record<string, ModuleProp>
  actions: StorageAction[]
  /**
   * Whether a `storage.ts` sits next to the definition.
   *
   * No module ships one yet, so every target is configuration-only for now: nothing reads or writes
   * content through a module. Actions and setup are gated on this, so that the admin area never
   * offers to run something that has no implementation behind it.
   */
  hasImplementation: boolean
}

/** A configured target: the module definition, plus how this site has it set up. */
export interface StorageTarget {
  id: string
  module: string
  isEnabled: boolean
  title: string
  description: string
  icon: string
  banner: string
  vendor: string
  website: string
  contentTypes: {
    activeTypes: string[]
    largeThreshold: string
  }
  assetDelivery: {
    isStreamingSupported: boolean
    isDirectAccessSupported: boolean
    streaming: boolean
    directAccess: boolean
  }
  versioning: {
    isSupported: boolean
    isForceEnabled: boolean
    enabled: boolean
  }
  setup?: {
    handler: string
    state: string
    values: Record<string, any>
  }
  props: Record<string, ModuleProp>
  config: Record<string, any>
  actions: StorageAction[]
}

/** The shape a target is written with. Every field is optional, i.e. it doubles as a patch. */
export interface StorageTargetInput {
  id: string
  isEnabled?: boolean
  contentTypes?: {
    activeTypes?: string[]
    largeThreshold?: string
  }
  assetDelivery?: {
    streaming?: boolean
    directAccess?: boolean
  }
  versioning?: {
    enabled?: boolean
  }
  config?: Record<string, any>
}

/** What a module implementation is expected to export, once any of them do. */
export interface StorageModule {
  /** Advance a multi-step setup process, returning what the admin area should do next. */
  setup?: (targetId: string, state: Record<string, any>) => Promise<Record<string, any>>
  /** Undo whatever `setup` configured, so that it can be started over. */
  setupDestroy?: (targetId: string) => Promise<void>
  /** Handlers named by the definition's actions. */
  [handler: string]: any
}

/**
 * Storage model
 *
 * A storage target is one module configured for one site — S3 for assets, git for pages, and so on.
 * Each module lives in `modules/storage/<key>/definition.yml`, which declares what it supports and
 * what it needs configured. Every site gets a row per module (see `syncSite`), so a target always
 * has a stable ID whether or not it has ever been enabled.
 *
 * Nothing dispatches content to targets yet: pages and assets are read and written straight from the
 * database, and no module ships an implementation. What this model handles is the configuration those
 * modules will read once they exist.
 */
class Storage {
  /** Definitions read from disk, refreshed by `refreshFromDisk()`. */
  definitions: StorageDefinition[] = []

  /** Implementations loaded by `ensureModule()`, keyed by module. */
  modules: Record<string, StorageModule> = {}

  /**
   * Load the storage module definitions from disk.
   */
  async refreshFromDisk(): Promise<void> {
    const storagePath = path.join(WIKI.SERVERPATH, 'modules/storage')
    const definitions: StorageDefinition[] = []
    try {
      for (const dir of await fs.readdir(storagePath)) {
        const raw = await fs.readFile(path.join(storagePath, dir, 'definition.yml'), 'utf8')
        const parsed = load(raw) as Record<string, any>
        // -> The directory name is the key, as it is for every other module type
        parsed.key = dir
        // -> Props carry a display `order`, applied once here so that every consumer — the admin
        //    area included — reads them in the order the module meant them to be shown in
        parsed.props = Object.fromEntries(
          Object.entries(parseModuleProps(parsed.props ?? {})).sort(
            ([, a], [, b]) => a.order - b.order
          )
        )
        // -> Declared as a map keyed by handler, which is far more readable in YAML than a list of
        //    objects, but the handler has to travel with the action for it to be callable
        parsed.actions = Object.entries(parsed.actions ?? {}).map(([handler, action]) => ({
          handler,
          ...(action as Omit<StorageAction, 'handler'>)
        }))
        parsed.versioning = {
          isSupported: false,
          isForceEnabled: false,
          defaultEnabled: false,
          ...parsed.versioning
        }
        parsed.hasImplementation = await this.hasImplementation(dir)
        definitions.push(parsed as StorageDefinition)
      }
      // -> The database target first, then alphabetically: it is the one every site starts with
      this.definitions = definitions.sort((a, b) =>
        a.key === DB_MODULE ? -1 : b.key === DB_MODULE ? 1 : a.title.localeCompare(b.title)
      )
      WIKI.logger.info(`Found ${this.definitions.length} storage modules [ OK ]`)
    } catch (err: any) {
      this.definitions = []
      WIKI.logger.error(
        `Could not read the storage module definitions at ${storagePath} [ FAILED ]`
      )
      WIKI.logger.error(err.message)
    }
  }

  /**
   * Whether the module has any code to run, as opposed to only a definition
   */
  async hasImplementation(key: string): Promise<boolean> {
    try {
      await fs.access(path.join(WIKI.SERVERPATH, 'modules/storage', key, 'storage.ts'))
      return true
    } catch {
      return false
    }
  }

  /**
   * A single definition, or null when nothing on disk declares that key
   */
  getDefinition(key: string): StorageDefinition | null {
    return this.definitions.find((d) => d.key === key) ?? null
  }

  /**
   * Give a site a row per installed module, and drop rows for modules no longer on disk.
   *
   * Existing rows are left alone: their settings belong to the site, whereas everything the
   * definition declares is read from disk on every request rather than copied into the row.
   */
  async syncSite(siteId: string): Promise<void> {
    const existing = await WIKI.db
      .select({ module: storageTable.module })
      .from(storageTable)
      .where(eq(storageTable.siteId, siteId))
    const existingKeys = existing.map((t) => t.module)
    const definedKeys = this.definitions.map((d) => d.key)

    for (const definition of this.definitions) {
      if (existingKeys.includes(definition.key)) {
        continue
      }
      await WIKI.db.insert(storageTable).values({
        siteId,
        module: definition.key,
        // -> Content has to land somewhere from the moment a site exists
        isEnabled: definition.key === DB_MODULE,
        contentTypes: {
          activeTypes: definition.contentTypes?.defaultTypesEnabled ?? [],
          largeThreshold: definition.contentTypes?.defaultLargeThreshold ?? '5MB'
        },
        assetDelivery: {
          streaming: definition.assetDelivery?.defaultStreamingEnabled ?? false,
          directAccess: definition.assetDelivery?.defaultDirectAccessEnabled ?? false
        },
        versioning: {
          enabled: definition.versioning.isForceEnabled || definition.versioning.defaultEnabled
        },
        config: this.buildConfig(definition.key),
        state: definition.setup ? { setup: 'notconfigured' } : {}
      })
    }

    // -> A module removed from disk should not linger in the admin list
    const orphaned = existingKeys.filter((key) => !definedKeys.includes(key))
    if (orphaned.length > 0) {
      await WIKI.db
        .delete(storageTable)
        .where(and(eq(storageTable.siteId, siteId), inArray(storageTable.module, orphaned)))
    }
  }

  /**
   * Register the installed storage modules for every site. Called at boot, after the sites cache.
   */
  async syncAllSites(): Promise<void> {
    WIKI.logger.info('Registering storage targets for all sites...')
    const sites = await WIKI.db.select({ id: sitesTable.id }).from(sitesTable)
    for (const site of sites) {
      await WIKI.models.storage.syncSite(site.id)
    }
    WIKI.logger.info(`Registered storage targets for ${sites.length} sites [ OK ]`)
  }

  /**
   * The stored target rows, without anything merged in from disk
   */
  async getTargets({
    siteId,
    enabledOnly = false
  }: { siteId?: string; enabledOnly?: boolean } = {}) {
    const conditions = [
      siteId ? eq(storageTable.siteId, siteId) : undefined,
      enabledOnly ? eq(storageTable.isEnabled, true) : undefined
    ].filter(Boolean)
    return WIKI.db
      .select()
      .from(storageTable)
      .where(conditions.length > 0 ? and(...conditions) : undefined)
  }

  /**
   * Every target of a site, in the order the admin area lists them.
   *
   * Config values are completed from the module's declared defaults, so a prop added to a module
   * after a target was configured is returned with its default rather than as a missing key.
   */
  async getSiteTargets(siteId: string): Promise<StorageTarget[]> {
    const rows = await this.getTargets({ siteId })
    const targets: StorageTarget[] = []
    // -> Driven by the definitions rather than by the rows, so that the list is ordered the same way
    //    and a module dropped on disk without a restart is simply absent instead of half-present
    for (const definition of this.definitions) {
      const row = rows.find((t) => t.module === definition.key)
      if (!row) {
        continue
      }
      const contentTypes = (row.contentTypes ?? {}) as Record<string, any>
      const assetDelivery = (row.assetDelivery ?? {}) as Record<string, any>
      const versioning = (row.versioning ?? {}) as Record<string, any>
      targets.push({
        id: row.id,
        module: definition.key,
        isEnabled: row.isEnabled,
        title: definition.title,
        description: definition.description,
        icon: definition.icon,
        banner: definition.banner,
        vendor: definition.vendor,
        website: definition.website,
        contentTypes: {
          activeTypes: contentTypes.activeTypes ?? [],
          largeThreshold: contentTypes.largeThreshold ?? '5MB'
        },
        assetDelivery: {
          isStreamingSupported: definition.assetDelivery?.isStreamingSupported ?? false,
          isDirectAccessSupported: definition.assetDelivery?.isDirectAccessSupported ?? false,
          streaming: assetDelivery.streaming ?? false,
          directAccess: assetDelivery.directAccess ?? false
        },
        versioning: {
          isSupported: definition.versioning.isSupported,
          isForceEnabled: definition.versioning.isForceEnabled,
          enabled: versioning.enabled ?? false
        },
        // -> Only offered for a module that can actually run its setup process
        ...(definition.setup &&
          definition.hasImplementation && {
            setup: {
              handler: definition.setup.handler,
              state: ((row.state ?? {}) as Record<string, any>).setup ?? 'notconfigured',
              values: this.buildSetupValues(definition, row.config as Record<string, any>)
            }
          }),
        props: definition.props,
        config: this.buildConfig(definition.key, {}, row.config as Record<string, any>),
        // -> Same reasoning as setup: an action with nothing behind it cannot be run
        actions: definition.hasImplementation ? definition.actions : []
      })
    }
    return targets
  }

  /**
   * A single target of a site, or null if there is no such target
   */
  async getSiteTargetById(siteId: string, id: string): Promise<StorageTarget | null> {
    return (await this.getSiteTargets(siteId)).find((t) => t.id === id) ?? null
  }

  /**
   * The values the setup form starts from: whatever the module stored, else its declared defaults.
   */
  buildSetupValues(
    definition: StorageDefinition,
    stored: Record<string, any> = {}
  ): Record<string, any> {
    const values: Record<string, any> = {}
    for (const [key, value] of Object.entries(definition.setup?.defaultValues ?? {})) {
      values[key] = stored[key] ?? value
    }
    return values
  }

  /**
   * Merge incoming config values onto the ones already stored, keeping only what the module declares.
   *
   * Read-only props are never taken from the client: they are declarations of something the server
   * does not support changing, so the stored value (or the module default) always wins.
   */
  buildConfig(
    moduleKey: string,
    incoming: Record<string, any> = {},
    existing: Record<string, any> = {}
  ): Record<string, any> {
    const props = this.getDefinition(moduleKey)?.props ?? {}
    const config: Record<string, any> = {}
    for (const [key, prop] of Object.entries(props)) {
      const current = existing[key] !== undefined ? existing[key] : prop.default
      config[key] = prop.readOnly || incoming[key] === undefined ? current : incoming[key]
    }
    return config
  }

  /**
   * Check incoming config values against what the module declares.
   *
   * The props are a runtime declaration read from a YAML file, so no JSON Schema can cover them —
   * without this, a boolean prop would happily store the string `"maybe"`.
   *
   * @returns The reason it is invalid, or null when it is fine
   */
  validateConfig(moduleKey: string, incoming: Record<string, any> = {}): string | null {
    const props = this.getDefinition(moduleKey)?.props ?? {}
    for (const [key, value] of Object.entries(incoming)) {
      const prop = props[key]
      // -> Unknown keys are dropped by buildConfig rather than refused: a module losing a prop must
      //    not make the admin area unable to save
      if (!prop || prop.readOnly || value === undefined) {
        continue
      }
      if (prop.enum) {
        // -> Enum entries are declared as `value` or `value|label`
        const allowed = prop.enum.map((entry) => entry.split('|')[0])
        if (!allowed.includes(`${value}`)) {
          return `"${value}" is not a valid value for ${prop.title}.`
        }
        continue
      }
      switch (prop.type) {
        case 'boolean':
          if (typeof value !== 'boolean') {
            return `${prop.title} must be true or false.`
          }
          break
        case 'number':
          if (typeof value !== 'number' || !Number.isFinite(value)) {
            return `${prop.title} must be a number.`
          }
          break
        default:
          if (typeof value !== 'string') {
            return `${prop.title} must be a string.`
          }
      }
    }
    return null
  }

  /**
   * Check a target patch against what its module supports.
   *
   * @returns The reason it is invalid, or null when it is fine
   */
  validateTarget(target: StorageTarget, patch: StorageTargetInput): string | null {
    const definition = this.getDefinition(target.module)!
    if (patch.isEnabled === false && target.module === DB_MODULE) {
      return 'The database storage target cannot be disabled, as content would have nowhere to live.'
    }
    if (patch.isEnabled === true && target.setup && target.setup.state !== 'configured') {
      return `${definition.title} cannot be enabled until its setup process is completed.`
    }
    const activeTypes = patch.contentTypes?.activeTypes
    if (activeTypes) {
      const unknown = activeTypes.find(
        (type) => !(CONTENT_TYPES as readonly string[]).includes(type)
      )
      if (unknown) {
        return `"${unknown}" is not a valid content type.`
      }
      if (target.module === DB_MODULE && !activeTypes.includes('pages')) {
        return 'The database storage target must keep holding pages.'
      }
    }
    const largeThreshold = patch.contentTypes?.largeThreshold
    if (largeThreshold !== undefined && !/^\d+(\.\d+)?\s?(B|KB|MB|GB|TB)$/i.test(largeThreshold)) {
      return `"${largeThreshold}" is not a valid size threshold. Use a size such as "5MB".`
    }
    return this.validateConfig(target.module, patch.config)
  }

  /**
   * Apply a patch to a target.
   *
   * Capabilities the module does not have are stored as off whatever was asked for, and versioning it
   * forces on is stored as on — the admin area disables those controls, but the values are the
   * module's to decide, not the client's.
   *
   * @param target The target as it currently stands, which the caller already has from validating
   * @returns Whether the target was written
   */
  async updateTarget(
    siteId: string,
    target: StorageTarget,
    patch: StorageTargetInput
  ): Promise<boolean> {
    const definition = this.getDefinition(target.module)!

    const values: Partial<typeof storageTable.$inferInsert> = {}
    if (patch.isEnabled !== undefined) {
      values.isEnabled = patch.isEnabled
    }
    if (patch.contentTypes) {
      values.contentTypes = {
        activeTypes: patch.contentTypes.activeTypes ?? target.contentTypes.activeTypes,
        largeThreshold: patch.contentTypes.largeThreshold ?? target.contentTypes.largeThreshold
      }
    }
    if (patch.assetDelivery) {
      values.assetDelivery = {
        streaming:
          definition.assetDelivery.isStreamingSupported &&
          (patch.assetDelivery.streaming ?? target.assetDelivery.streaming),
        directAccess:
          definition.assetDelivery.isDirectAccessSupported &&
          (patch.assetDelivery.directAccess ?? target.assetDelivery.directAccess)
      }
    }
    if (patch.versioning) {
      values.versioning = {
        enabled:
          definition.versioning.isForceEnabled ||
          (definition.versioning.isSupported &&
            (patch.versioning.enabled ?? target.versioning.enabled))
      }
    }
    if (patch.config !== undefined) {
      values.config = this.buildConfig(target.module, patch.config, target.config)
    }
    if (Object.keys(values).length < 1) {
      return false
    }

    const result = await WIKI.db
      .update(storageTable)
      .set(values)
      .where(and(eq(storageTable.siteId, siteId), eq(storageTable.id, target.id)))
    return (result.rowCount ?? 0) > 0
  }

  /**
   * Ensure a module's implementation is loaded
   *
   * @returns The implementation, or null when the module has none or it failed to load
   */
  async ensureModule(key: string): Promise<StorageModule | null> {
    if (this.modules[key]) {
      return this.modules[key]
    }
    if (!this.getDefinition(key)?.hasImplementation) {
      return null
    }
    try {
      // -> Extension-sensitive dynamic import, invisible to the type checker
      this.modules[key] = (await import(`../modules/storage/${key}/storage.ts`)).default
      WIKI.logger.debug(`Activated storage module ${key} [ OK ]`)
      return this.modules[key]
    } catch (err: any) {
      WIKI.logger.warn(`Failed to load storage module ${key} [ FAILED ]`)
      WIKI.logger.warn(err)
      return null
    }
  }

  /**
   * Run one of the actions a module declares.
   *
   * @throws When the module cannot be loaded or does not implement the handler
   */
  async executeAction(target: StorageTarget, handler: string): Promise<void> {
    const mod = await this.ensureModule(target.module)
    if (!mod) {
      throw new Error(`The ${target.title} storage module has no implementation installed.`)
    }
    if (typeof mod[handler] !== 'function') {
      throw new Error(`The ${target.title} storage module does not implement "${handler}".`)
    }
    await mod[handler](target)
  }

  /**
   * Advance a module's setup process.
   *
   * @returns What the admin area should do next, as decided by the module
   * @throws When the module cannot be loaded or has no setup process
   */
  async runSetup(target: StorageTarget, state: Record<string, any>): Promise<Record<string, any>> {
    const mod = await this.ensureModule(target.module)
    if (!mod?.setup) {
      throw new Error(`The ${target.title} storage module has no setup process.`)
    }
    return mod.setup(target.id, state)
  }

  /**
   * Undo a module's setup, so that it can be started over.
   *
   * @throws When the module cannot be loaded or has no setup process
   */
  async destroySetup(target: StorageTarget): Promise<void> {
    const mod = await this.ensureModule(target.module)
    if (!mod?.setupDestroy) {
      throw new Error(`The ${target.title} storage module has no setup process.`)
    }
    await mod.setupDestroy(target.id)
  }
}

export const storage = new Storage()