/**
 * Host-side ApiProxy implementation. Signature discipline: unary takes the
 * narrow RpcRequest<P> and echoes request.rpcId on the RpcResponse<T>.
 */

import { homedir } from 'node:os'
import { dirname } from 'node:path'
import type { Context } from '@deepseek-ai/cordis'
import type { ModelSelection } from '@deepseek-ai/dsh-agent'
import type {} from '@deepseek-ai/dsh-agent-presets/types'
import type { SessionId } from '@deepseek-ai/dsh-session'
import { isUserInvocable } from '@deepseek-ai/dsh-skill'
import {
  InvalidPresetIdError, PresetExistsError,
  PresetNotWritableError, UnknownPresetError,
} from '@deepseek-ai/dsh-agent-presets'
import type {
  ApiProxy, ConfigurableProviderView, CredentialView,
  SettingsNamespaceView,
} from './api/index.ts'
import { buildModelCatalog } from '@deepseek-ai/dsh-api-session-controller'
import { SessionQueryError } from '@deepseek-ai/dsh-session-query'
import {
  DEFAULT_SESSION_LOG_COMPRESSION_LEVEL,
  flushLiveSessionLog,
  sessionLogExportDeps,
  sessionLogZipFilename,
  streamSessionLogZip,
  type SessionLogExportReady,
  type SessionLogCompressionLevel,
} from './session-export.ts'
import type { SessionRawArtifact } from '@deepseek-ai/dsh-session-persistence'
// Type-only edges: resolve the command-change stream and `ctx.get('skills')`.
import type {} from '@deepseek-ai/dsh-commands'
import type {} from '@deepseek-ai/dsh-skill'
// The settings/credentials seams: brand guards run at this wire boundary; the
// service reads stay optional (`ctx.get`) so a composition without either
// provider still serves every other domain.
import { SettingsConflictError, settingsNamespace } from '@deepseek-ai/dsh-settings'
import type { SettingsDescriptor, SettingsNamespace, SettingsPathOp } from '@deepseek-ai/dsh-settings'
import { credentialRef } from '@deepseek-ai/dsh-credentials'
import type { ScopeKey } from '@deepseek-ai/dsh-scope'
import type { RpcError, RpcRequest, RpcResponse } from './api/rpc.ts'
import { DirectoryPickerError } from '@deepseek-ai/dsh-host-directory-picker'
import { canOpenNativePath, openNativePath, openNativeTextFile } from './native-path-opener.ts'

/** Read live abort state across awaits without treating it as synchronously immutable. */
function isAborted(signal: AbortSignal): boolean {
  return signal.aborted
}

/** Wrap an ok result echoing the request's rpcId. */
function ok<T>(request: RpcRequest<unknown>, value: T): RpcResponse<T> {
  return { rpcId: request.rpcId, result: { ok: true, value } }
}

/** Wrap an error result echoing the request's rpcId. */
function err<T>(request: RpcRequest<unknown>, error: RpcError): RpcResponse<T> {
  return { rpcId: request.rpcId, result: { ok: false, error } }
}

/** Map a browse-primitive failure onto the wire error vocabulary (unknown throws stay internal). */
function directoryError(error: unknown): RpcError {
  if (error instanceof DirectoryPickerError) {
    return { code: error.code, message: error.message, details: { path: error.path } }
  }
  return { code: 'internal', message: error instanceof Error ? error.message : String(error), details: {} }
}

/** Deployment metadata and Host integrations consumed by the API implementation. */
export interface ApiProxyDefaults {
  /** Current deployment model selection reported by `host.describe`. */
  defaultModelSelection: () => ModelSelection
  /** Project hint reported by `host.describe`; must match Session Controller's default cwd. */
  cwd: string
  /** Native open-with-default-application; injectable for carrier tests. */
  openPath?: (path: string, signal: AbortSignal) => Promise<void>
  /** Native text-editor handoff; injectable for settings-document tests. */
  openTextFile?: (path: string, signal: AbortSignal) => Promise<void>
  /** Validated DEFLATE level for session-log ZIP entries; defaults to 6. */
  sessionExportCompressionLevel?: SessionLogCompressionLevel
  /**
   * Whether handing a path to the native opener can work at all — the
   * `hasDocument` capability the preset roster reports, and the switch
   * between opening a preset directory and answering its path as text.
   * Absent, an injected `openPath` counts as openable and everything else
   * falls back to platform detection ({@link canOpenNativePath}).
   */
  canOpenPath?: () => boolean
}

/** The roster is absent: this deployment composes no agent presets at all. */
function noRoster(agentPreset: string): RpcError {
  return {
    code: 'agent-preset-not-found',
    message: 'this deployment composes no agent presets',
    details: { agentPreset, available: [] },
  }
}

/** Map one authoring/roster failure onto its wire code. */
function presetError(agentPreset: string, error: unknown): RpcError {
  if (error instanceof UnknownPresetError) {
    return {
      code: 'agent-preset-not-found',
      message: error.message,
      details: { agentPreset: error.presetId, available: [...error.available] },
    }
  }
  if (error instanceof PresetNotWritableError) {
    return { code: 'agent-preset-read-only', message: error.message, details: { agentPreset, reason: error.message } }
  }
  if (error instanceof InvalidPresetIdError || error instanceof PresetExistsError) {
    return { code: 'agent-preset-invalid', message: error.message, details: { agentPreset, reason: error.message } }
  }
  return { code: 'internal', message: `agent preset "${agentPreset}": ${String(error)}`, details: {} }
}

/**
 * Implement ApiProxy over a composed host context.
 * @param ctx - a context with the Host spine mounted.
 * @param defaults - host routing and project-directory defaults.
 * @returns the ApiProxy implementation.
 */
export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiProxy {
  const sessionExportCompressionLevel = defaults.sessionExportCompressionLevel
    ?? DEFAULT_SESSION_LOG_COMPRESSION_LEVEL
  /** Resolve a Session's live or standing preset scope without resuming it. */
  async function sessionScopeFor(
    sessionId: SessionId,
    agentPreset: string | undefined,
  ): Promise<ScopeKey | undefined> {
    const live = ctx.get('agents')?.get(sessionId)
    if (live !== undefined) return live
    const presets = ctx.get('agentPresets')
    if (presets === undefined) return undefined
    try {
      return await presets.standingKeyFor(agentPreset)
    } catch {
      // An unknown or unusable recorded preset falls back to the global registry.
      return undefined
    }
  }

  /** Missing-service report shared by the settings domain (skills-domain stance). */
  function settingsAbsent(): RpcError {
    return { code: 'internal', message: 'settings service is absent: this deployment does not mount a settings provider (e.g. @deepseek-ai/dsh-settings-file) in its composition', details: {} }
  }

  /** Open one Host-resolved target and map native failures onto the wire vocabulary. */
  async function openTarget(
    request: RpcRequest<unknown>, path: string, signal: AbortSignal,
    open: (path: string, signal: AbortSignal) => Promise<void>,
  ): Promise<RpcResponse<{ opened: true }>> {
    try {
      await open(path, signal)
      return ok(request, { opened: true as const })
    } catch (error: unknown) {
      if (signal.aborted) {
        return err(request, {
          code: 'cancelled',
          message: 'path open was aborted',
          details: {},
        })
      }
      return err(request, {
        code: 'internal',
        message: `path open failed: ${error instanceof Error ? error.message : String(error)}`,
        details: {},
      })
    }
  }

  /** Open one Host-resolved path with its default application. */
  function openPath(
    request: RpcRequest<unknown>, path: string, signal: AbortSignal,
  ): Promise<RpcResponse<{ opened: true }>> {
    const open = defaults.openPath
      ?? ((target: string, openSignal: AbortSignal) => openNativePath(target, openSignal))
    return openTarget(request, path, signal, open)
  }

  /** Open one Host-resolved text document in a native editor. */
  function openTextFile(
    request: RpcRequest<unknown>, path: string, signal: AbortSignal,
  ): Promise<RpcResponse<{ opened: true }>> {
    const open = defaults.openTextFile
      ?? ((target: string, openSignal: AbortSignal) => openNativeTextFile(target, openSignal))
    return openTarget(request, path, signal, open)
  }

  /** Whether this deployment can hand a path to a native opener at all. */
  function canOpenPaths(): boolean {
    if (defaults.canOpenPath !== undefined) return defaults.canOpenPath()
    // An injected opener is by definition usable; otherwise ask the platform.
    return defaults.openPath !== undefined || canOpenNativePath()
  }

  /** Missing-service report shared by the credentials domain. */
  function credentialsAbsent(): RpcError {
    return { code: 'internal', message: 'credentials service is absent: this deployment does not mount a credential provider (e.g. @deepseek-ai/dsh-credentials-local) in its composition', details: {} }
  }

  /** Map one redacted settings descriptor to its wire view. */
  function namespaceView(descriptor: SettingsDescriptor): SettingsNamespaceView {
    return {
      ns: String(descriptor.ns),
      schema: descriptor.schema,
      value: descriptor.value,
      ...descriptor.base === undefined ? {} : { base: descriptor.base },
      ...descriptor.user === undefined ? {} : { user: descriptor.user },
      applies: descriptor.applies,
      secrets: (descriptor.secrets ?? []).map(secret => ({ path: [...secret.path], set: secret.set })),
      revision: descriptor.revision,
    }
  }

  /**
   * Run one settings write (merge or wholesale replace) and acknowledge with
   * the namespace's new redacted view. Every seam refusal — unknown or invalid
   * namespace, read-only provider, schema validation, storage — becomes one
   * `settings-rejected` carrying the seam's own message.
   */
  async function settingsWrite(
    request: RpcRequest<unknown>,
    ns: string,
    mode: 'update' | 'replace' | 'mutate',
    section: object,
    expectedRevision?: number,
  ): Promise<RpcResponse<SettingsNamespaceView>> {
    const settings = ctx.get('settings')
    if (settings === undefined) return err(request, settingsAbsent())
    const rejected = (error: unknown): RpcResponse<SettingsNamespaceView> => {
      // A stale writer is its own outcome, not a malformed request: the client
      // must re-read and re-apply rather than treat the write as invalid.
      if (error instanceof SettingsConflictError) {
        return err(request, {
          code: 'settings-conflict',
          message: error.message,
          details: { ns, expected: error.expected, actual: error.actual },
        })
      }
      return err(request, {
        code: 'settings-rejected',
        message: error instanceof Error ? error.message : String(error),
        details: { ns },
      })
    }
    let branded: SettingsNamespace
    try {
      branded = settingsNamespace(ns)
    } catch (error: unknown) {
      // A malformed name can address no registration, so it fails exactly as
      // an unregistered one does.
      return rejected(error)
    }
    try {
      if (mode === 'update') await settings.update(branded, section, expectedRevision)
      else if (mode === 'replace') await settings.replace(branded, section, expectedRevision)
      else await settings.mutate(branded, section as SettingsPathOp[], expectedRevision)
    } catch (error: unknown) {
      return rejected(error)
    }
    const descriptor = settings.describe({ redactSecrets: true }).find(candidate => candidate.ns === branded)
    if (descriptor === undefined) {
      // The write committed but the namespace vanished before this read: only
      // a concurrent registrant disposal can produce it.
      return err(request, { code: 'internal', message: `settings namespace "${ns}" was disposed after the ${mode}`, details: {} })
    }
    return ok(request, namespaceView(descriptor))
  }

  return {
    host: {
      describe(request) {
        // TODO(apiproxy-version): read the version from apps/cli/package.json.
        const selection = defaults.defaultModelSelection()
        return Promise.resolve(ok(request, {
          version: '0.0.1',
          // This must match the default cwd supplied to Session Controller so
          // the UI's project hint names where a cwd-less create request lands.
          cwd: defaults.cwd,
          // Read live for the same reason: this is what the NEXT session will
          // start from, so a saved default has to be what it reports.
          provider: selection.provider,
          model: selection.model,
          attachedSessions: ctx.agents.list().length,
          home: homedir(),
          canOpenPath: canOpenPaths(),
        }))
      },

      async pickDirectory(request, signal) {
        const capability = ctx.directoryPicker.capability()
        if (capability.kind !== 'native') {
          return err(request, {
            code: 'directory-picker-unavailable',
            message: `host.pickDirectory needs the native capability; the composed picker serves "${capability.kind}"`,
            details: { capability: capability.kind },
          })
        }
        try {
          const path = await capability.pick(signal)
          return ok(request, { path })
        } catch (error: unknown) {
          if (signal.aborted) {
            return err(request, {
              code: 'cancelled',
              message: 'directory picker was aborted',
              details: {},
            })
          }
          return err(request, {
            code: 'internal',
            message: `directory picker failed: ${error instanceof Error ? error.message : String(error)}`,
            details: {},
          })
        }
      },

      async listDirectory(request, signal) {
        const capability = ctx.directoryPicker.capability()
        if (capability.kind !== 'browse') {
          return err(request, {
            code: 'directory-picker-unavailable',
            message: `host.listDirectory needs the browse capability; the composed picker serves "${capability.kind}"`,
            details: { capability: capability.kind },
          })
        }
        try {
          // The carrier's signal follows the caller: a disconnect or timeout
          // stops the backend's directory scan instead of outliving it.
          return ok(request, await capability.list(request.payload.path, signal))
        } catch (error: unknown) {
          // An abort is the caller's own timeout/disconnect, not a server failure.
          if (signal.aborted) {
            return err(request, { code: 'cancelled', message: 'directory listing was aborted', details: {} })
          }
          return err(request, directoryError(error))
        }
      },

      async createDirectory(request) {
        const capability = ctx.directoryPicker.capability()
        if (capability.kind !== 'browse') {
          return err(request, {
            code: 'directory-picker-unavailable',
            message: `host.createDirectory needs the browse capability; the composed picker serves "${capability.kind}"`,
            details: { capability: capability.kind },
          })
        }
        try {
          return ok(request, { path: await capability.createDirectory(request.payload.path, request.payload.name) })
        } catch (error: unknown) {
          return err(request, directoryError(error))
        }
      },

      async openPath(request, signal) {
        return openPath(request, request.payload.path, signal)
      },
    },

    agentPresets: {
      // Only the desktop opener remains here: the roster, selection, and
      // authoring calls are the AgentPresets service's own Remote namespace.
      async openDocument(request, signal) {
        const { agentPreset } = request.payload
        const presets = ctx.get('agentPresets')
        if (presets === undefined) return err(request, noRoster(agentPreset))
        try {
          const preset = await presets.resolve(agentPreset)
          // Same line as copy/remove draw: the shipped install is not the
          // user's to manage, and pointing an editor into it invites edits an
          // upgrade will silently overwrite.
          if (preset.trust !== 'user') {
            throw new PresetNotWritableError(preset.id, 'it ships with the deployment')
          }
          // The id resolved against the Host's own roots is what selects the
          // directory — no browser payload carries a path in either direction
          // unless the deployment has no opener to hand it to.
          const directory = dirname(preset.path)
          if (!canOpenPaths()) return ok(request, { opened: false as const, path: directory })
          return await openPath(request, directory, signal)
        } catch (error: unknown) {
          return err(request, presetError(agentPreset, error))
        }
      },
    },

    skills: {
      // Skill lookup never creates or resumes an agent: the session address
      // resolves to a canonical cwd from the host-resident session header, and
      // the view scope is the live agent or the preset's standing key.
      async list(request) {
        const { sessionId } = request.payload
        let cwd: string | undefined
        let agentPreset: string | undefined
        try {
          using observation = await ctx.sessionQuery.observeSession(sessionId)
          if (observation.projections === undefined) {
            throw new Error('skill catalog requires a projected Session observation')
          }
          cwd = observation.header.cwd
          agentPreset = observation.projections.values.agentPreset ?? undefined
        } catch (error: unknown) {
          if (error instanceof SessionQueryError
            && error.code === 'SESSION_QUERY_SESSION_NOT_FOUND') {
            return err(request, {
              code: 'session-not-found',
              message: `session "${sessionId}" not found`,
              details: { sessionId },
            })
          }
          return err(request, {
            code: 'internal',
            message: `session "${sessionId}" could not be inspected: ${String(error)}`,
            details: {},
          })
        }
        if (cwd === undefined) {
          // Every served session records its project at create time; a
          // cwd-less header is a pre-project legacy log (not served).
          return err(request, { code: 'internal', message: `session "${sessionId}" has no project cwd`, details: {} })
        }
        // The host registry is layered per scope and serves every session. A
        // composition may still realm-mount its own registry instead; that
        // instance is invisible to host contexts, so address it through the
        // live agent (`agents.get` keeps the no-side-effect stance above).
        const live = ctx.agents.get(sessionId)
        const presets = ctx.get('agentPresets')
        const scoped = live === undefined ? undefined : presets?.serviceFor(live, 'skills')
        // A missing service means no composition mounts dsh-skill, not an
        // empty catalog. `ctx.get` also
        // keeps this handler independent of the gateway plugin's inject list
        // (an undeclared `ctx.skills` property read fails the reflect proxy).
        const skillRegistry = scoped ?? ctx.get('skills')
        if (skillRegistry === undefined) {
          return err(request, { code: 'internal', message: 'skill registry is absent: neither this session\'s agent preset nor the host composition mounts @deepseek-ai/dsh-skill', details: {} })
        }
        // Resolve the live or recorded preset scope so the catalog matches the
        // Session composition without resuming its Agent.
        const scope = await sessionScopeFor(sessionId, agentPreset)
        try {
          const skills = (await skillRegistry.list({ cwd, scope })).filter(isUserInvocable)
          return ok(request, {
            skills: skills.map(skill => ({
              name: skill.name,
              description: skill.description,
              ...skill.whenToUse === undefined ? {} : { whenToUse: skill.whenToUse },
              modelInvocable: skill.invocation.modelInvocable,
            })),
          })
        } catch (error: unknown) {
          return err(request, { code: 'internal', message: `skill listing failed: ${String(error)}`, details: {} })
        }
      },
    },

    settings: {
      describe(request) {
        const settings = ctx.get('settings')
        if (settings === undefined) return Promise.resolve(err(request, settingsAbsent()))
        return Promise.resolve(ok(request, {
          writable: settings.writable,
          hasDocument: settings.documentPath !== undefined,
          namespaces: settings.describe({ redactSecrets: true }).map(namespaceView),
        }))
      },
      async openDocument(request, signal) {
        const settings = ctx.get('settings')
        if (settings === undefined) return err(request, settingsAbsent())
        if (isAborted(signal)) {
          return err(request, {
            code: 'cancelled',
            message: 'settings document open was aborted',
            details: {},
          })
        }
        let path: string | undefined
        try {
          path = await settings.prepareDocument()
        } catch (error: unknown) {
          if (isAborted(signal)) {
            return err(request, {
              code: 'cancelled',
              message: 'settings document preparation was aborted',
              details: {},
            })
          }
          return err(request, {
            code: 'internal',
            message: `settings document preparation failed: ${error instanceof Error ? error.message : String(error)}`,
            details: {},
          })
        }
        if (path === undefined) {
          return err(request, {
            code: 'internal',
            message: 'settings provider has no local document to open',
            details: {},
          })
        }
        if (isAborted(signal)) {
          return err(request, {
            code: 'cancelled',
            message: 'settings document open was aborted',
            details: {},
          })
        }
        return openTextFile(request, path, signal)
      },
      update: request => settingsWrite(request, request.payload.ns, 'update', request.payload.patch, request.payload.expectedRevision),
      replace: request => settingsWrite(request, request.payload.ns, 'replace', request.payload.section, request.payload.expectedRevision),
      mutate: request => settingsWrite(request, request.payload.ns, 'mutate', request.payload.ops, request.payload.expectedRevision),
    },

    credentials: {
      async describe(request) {
        const credentials = ctx.get('credentials')
        if (credentials === undefined) return err(request, credentialsAbsent())
        const entries = await Promise.all(request.payload.refs.map(async (ref) => {
          const info = await credentials.describe(credentialRef(ref))
          const view: CredentialView = {
            configured: info.configured,
            ...info.source === undefined ? {} : { source: info.source },
            writable: info.writable,
          }
          return [ref, view] as const
        }))
        return ok(request, { credentials: Object.fromEntries(entries) })
      },

      async set(request) {
        const credentials = ctx.get('credentials')
        if (credentials === undefined) return err(request, credentialsAbsent())
        const { ref, value } = request.payload
        try {
          await credentials.set(credentialRef(ref), value)
        } catch (error: unknown) {
          return err(request, {
            code: 'credential-rejected',
            message: error instanceof Error ? error.message : String(error),
            details: { ref },
          })
        }
        return ok(request, {})
      },

      async unset(request) {
        const credentials = ctx.get('credentials')
        if (credentials === undefined) return err(request, credentialsAbsent())
        const { ref } = request.payload
        try {
          await credentials.unset(credentialRef(ref))
        } catch (error: unknown) {
          return err(request, {
            code: 'credential-rejected',
            message: error instanceof Error ? error.message : String(error),
            details: { ref },
          })
        }
        return ok(request, {})
      },
    },

    llm: {
      providers(request) {
        const registered = ctx.llm.listProviders()
        const active = new Set(registered.map(provider => provider.id))
        const directory = ctx.llm.listConfigurableProviders()
        const declared = new Set(directory.map(entry => entry.provider))
        const views: ConfigurableProviderView[] = directory.map(entry => ({
          provider: entry.provider,
          displayName: entry.displayName,
          settingsNs: entry.settingsNs,
          settingsPath: [...entry.settingsPath],
          active: active.has(entry.provider),
          ...entry.declared === undefined ? {} : { declared: entry.declared },
        }))
        // Routes registered without a directory declaration still appear —
        // they exist and serve models — just with no settings address. No
        // adapter claimed them, so nothing can say whether they are shipped.
        for (const provider of registered) {
          if (declared.has(provider.id)) continue
          views.push({
            provider: provider.id,
            displayName: provider.name,
            settingsNs: '',
            settingsPath: [],
            active: true,
          })
        }
        return Promise.resolve(ok(request, { providers: views }))
      },

      async models(request) {
        return ok(request, await buildModelCatalog(ctx, defaults.defaultModelSelection()))
      },

      async discoverModels(request, signal) {
        const { settingsNs, provider, baseURL, api, apiKey } = request.payload
        try {
          const models = await ctx.llm.discoverModels(settingsNs, {
            ...provider === undefined ? {} : { provider },
            ...baseURL === undefined ? {} : { baseURL },
            ...api === undefined ? {} : { api },
            ...apiKey === undefined ? {} : { apiKey },
            ...signal === undefined ? {} : { signal },
          })
          return ok(request, { models })
        } catch (error: unknown) {
          // Every failure here is the user's next move, not a transport fault:
          // a wrong endpoint, a rejected key, or a protocol with no listing all
          // end at the same place — fill the models in by hand. The details
          // repeat only what the caller already sent, never the credential.
          return err(request, {
            code: 'model-discovery-failed',
            message: error instanceof Error ? error.message : String(error),
            details: { settingsNs, ...baseURL === undefined ? {} : { baseURL } },
          })
        }
      },
    },

    downloads: {
      async sessionLog(request, signal) {
        // Clean error path first: missing services answer 500 and a missing
        // root artifact 404 before any zip byte is produced. The root content
        // read here is reused as the first zip entry, so nothing is read twice.
        const deps = sessionLogExportDeps(ctx)
        if (deps.sessionQuery === undefined || deps.sessionPersistence === undefined || deps.attachments === undefined) {
          return new Response(
            'session log export is unavailable: missing session-query, session-persistence, or attachments service',
            { status: 500 },
          )
        }
        if (!deps.sessionPersistence.supportsRawArtifacts) {
          return new Response(
            'session log export is unavailable: the persistence backend does not expose per-session raw artifacts',
            { status: 501 },
          )
        }
        const ready: SessionLogExportReady = {
          sessionQuery: deps.sessionQuery,
          sessionPersistence: deps.sessionPersistence,
          attachments: deps.attachments,
          sessions: deps.sessions,
        }
        let root: SessionRawArtifact | undefined
        try {
          await flushLiveSessionLog(deps, request.sessionId, signal)
          root = await deps.sessionPersistence.readRaw(request.sessionId, signal)
          signal.throwIfAborted()
        } catch {
          signal.throwIfAborted()
          // Root preparation failure: answer 500 without echoing the error,
          // which may carry absolute host paths into the browser error bar.
          return new Response('session log export failed to prepare the stored artifact', { status: 500 })
        }
        if (root === undefined) {
          return new Response('session not found', { status: 404 })
        }
        return new Response(
          streamSessionLogZip(
            ready,
            root,
            request.sessionId,
            request.includeDescendants === true,
            sessionExportCompressionLevel,
            signal,
          ),
          {
            headers: {
              'content-type': 'application/zip',
              'content-disposition': `attachment; filename="${sessionLogZipFilename(request.sessionId)}"`,
            },
          },
        )
      },
    },
  }
}