/**
 * Materialization of one provider route's model catalog. The installed pi-ai
 * catalog supplies defaults keyed by model id, and a profile's own model
 * entries override them field by field, so a route naming a catalog provider
 * stays configuration-free while a route pi-ai has never heard of is fully
 * describable from `settings.yaml`.
 *
 * Every pi-ai `Model` field the harness cannot default is required here rather
 * than at request time: an unserviceable route fails while its configuration is
 * being resolved, which is the earliest point that can name the offending key.
 *
 * @module dsh-llm-pi-ai/catalog
 */

import { builtinProviders, getBuiltinModels, getBuiltinProviders } from '@earendil-works/pi-ai/providers/all'
import type { BuiltinProvider } from '@earendil-works/pi-ai/providers/all'
import type {
  Api,
  Model,
  ModelCost,
  ModelThinkingLevel,
  OpenAICompletionsCompat,
  Provider,
  ThinkingLevelMap,
} from '@earendil-works/pi-ai'

/**
 * Pricing for a model the installed catalog does not describe. The harness
 * never reads pi-ai's cost metadata — `replay.ts` zeroes it and no consumer
 * reports spend — so this is the absence of a fact, not a configurable rate.
 */
const NO_COST: ModelCost = { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 }

/**
 * Input modalities for a model the installed catalog does not describe. The
 * request converter keeps only text blocks, so text is the adapter's actual
 * capability rather than a deployment choice.
 */
const TEXT_ONLY: Model<Api>['input'] = ['text']

/**
 * Every pi-ai thinking level, in pi-ai's canonical escalation order. The
 * `Record` key type is a drift gate: a pi-ai upgrade that adds or removes a
 * level fails compilation here naming the drifted key, instead of silently
 * narrowing what a profile may declare.
 */
const THINKING_LEVEL_GATE: Record<ModelThinkingLevel, true> = {
  off: true,
  minimal: true,
  low: true,
  medium: true,
  high: true,
  xhigh: true,
  max: true,
}

/** Every pi-ai thinking level a profile may declare, in escalation order. */
export const THINKING_LEVELS = Object.keys(THINKING_LEVEL_GATE) as readonly ModelThinkingLevel[]

/** The `compat.thinkingFormat` spellings pi-ai accepts on an `openai-completions` model. */
type PiThinkingFormat = NonNullable<OpenAICompletionsCompat['thinkingFormat']>

/**
 * pi-ai thinking formats a profile cannot name: both drive the request through
 * `chatTemplateKwargs`, which this configuration does not expose.
 */
type WithheldThinkingFormat = 'chat-template' | 'qwen-chat-template'

/** One reasoning-dispatch wire format a profile may name. */
export type PiAiThinkingFormat = Exclude<PiThinkingFormat, WithheldThinkingFormat>

/**
 * The nameable reasoning-dispatch formats, most-reached first. The `Record`
 * key type is a drift gate: a pi-ai upgrade that adds a format (0.84 added
 * `baseten`) fails compilation here until the format is classified as offered
 * here or withheld above, so the offer never silently lags the upstream set.
 */
const THINKING_FORMAT_GATE: Record<PiAiThinkingFormat, true> = {
  'openai': true,
  'deepseek': true,
  'openrouter': true,
  'together': true,
  'zai': true,
  'qwen': true,
  'string-thinking': true,
  'ant-ling': true,
}

/** Reasoning-dispatch wire formats a profile may name, most-reached first. */
export const SUPPORTED_THINKING_FORMATS = Object.keys(THINKING_FORMAT_GATE) as readonly PiAiThinkingFormat[]

let providerIndex: Map<string, Provider> | undefined

/**
 * Installed catalog providers by id, constructed once. Each entry owns the API
 * implementations for its own models, which is why a catalog route reuses this
 * provider instead of being rebuilt from parts.
 * @returns the catalog provider index.
 */
function catalogProviders(): Map<string, Provider> {
  providerIndex ??= new Map(builtinProviders().map(provider => [provider.id, provider]))
  return providerIndex
}

/**
 * The installed catalog provider for one route, when pi-ai ships one.
 * @param provider - provider route key.
 * @returns the catalog provider, or `undefined` for a route pi-ai does not ship.
 */
export function catalogProvider(provider: string): Provider | undefined {
  return catalogProviders().get(provider)
}

/**
 * Every provider route the installed pi-ai catalog ships.
 * @returns the catalog provider ids.
 */
export function catalogProviderIds(): readonly string[] {
  return getBuiltinProviders()
}

/**
 * The installed catalog models for one route, indexed by model id.
 * @param provider - provider route key.
 * @returns catalog models by id; empty for a route pi-ai does not ship.
 */
export function catalogModels(provider: string): Map<string, Model<Api>> {
  if (!catalogProviders().has(provider)) return new Map()
  const models = getBuiltinModels(provider as BuiltinProvider) as Model<Api>[]
  return new Map(models.map(model => [model.id, model]))
}

/**
 * Selectable reasoning efforts for one model: each key is a level the model
 * offers (and selectors show), and its value is the wire spelling dispatch
 * sends for it. `off` alone may leave its value empty — "supported, send
 * nothing" — because for most providers not thinking is the parameter's
 * absence; every other declared level must name a wire value. A level absent
 * from the dict is not offered.
 */
export type PiAiReasoningEfforts = Partial<Record<ModelThinkingLevel, string | null>>

/**
 * Reasoning-dispatch compatibility switches, set on the route (its models'
 * default) or per model (winning over the route). Only the switches pi-ai's
 * reasoning dispatch reads are offered; the rest of pi-ai's compat surface
 * keeps its baseURL-derived auto-detection. pi-ai types both fields only on
 * `OpenAICompletionsCompat` — the other wire protocols define their reasoning
 * fields in the protocol itself — so resolution rejects a model-level switch
 * anywhere else, while a route-level default skips past models it cannot fit.
 */
export interface PiAiCompatProfile {
  /** Reasoning parameter format the endpoint expects; absent keeps the catalog entry's, then pi-ai's baseURL-derived guess. */
  thinkingFormat?: PiAiThinkingFormat
  /** Whether the endpoint accepts `reasoning_effort`; absent keeps the catalog entry's, then pi-ai's baseURL-derived guess. */
  supportsReasoningEffort?: boolean
}

/** One configured model entry: an id plus the catalog fields it overrides. */
export interface PiAiModelProfile {
  /** Model id sent to the provider and accepted by {@link GenerateOptions.model}. */
  id: string
  /** Display name for selectors; defaults to the catalog name, then the id. */
  name?: string
  /** Maximum combined request and response context in tokens. */
  contextWindow?: number
  /**
   * Maximum output tokens. Configuring one also makes it this model's
   * per-request default; a value inherited from the installed catalog, or the
   * route's fallback, is the model's capability and never becomes a request
   * default on its own.
   */
  maxTokens?: number
  /**
   * Selectable reasoning efforts. Absent inherits the installed catalog
   * entry's capability (a hand-declared model has none and does not reason);
   * `false` declares a non-reasoning model, which is how a profile strips
   * reasoning from a catalog model its gateway cannot serve; a non-empty dict
   * declares the offered levels and their wire spellings.
   */
  reasoningEfforts?: false | PiAiReasoningEfforts
  /** Reasoning-dispatch switches for this model, winning over the route's. */
  compat?: PiAiCompatProfile
}

/**
 * Customization of one installed catalog model, keyed by its id in the
 * route's `modelOverrides` dict — the same fields a `models` entry may set,
 * with the id living in the key. Unlike a `models` list, overrides leave the
 * rest of the catalog serving untouched, which is what makes "correct one
 * model, keep the other thirty-seven" a three-line edit.
 */
export type PiAiModelOverride = Omit<PiAiModelProfile, 'id'>

/** The route-level facts model materialization reads. */
export interface RouteCatalogRequest {
  /** Provider route key, stamped onto every materialized model. */
  provider: string
  /** Wire protocol override; absent defers to each catalog model's own API. */
  api?: string
  /** Endpoint override; absent defers to the catalog model, then the catalog provider. */
  baseURL?: string
  /** Configured catalog; absent means the whole installed catalog for this route. */
  models?: readonly PiAiModelProfile[]
  /** Installed-catalog customizations by model id; only meaningful while `models` is absent. */
  modelOverrides?: Readonly<Record<string, PiAiModelOverride>>
  /** Reasoning-dispatch switches for every `openai-completions` model on the route; entries override per field. */
  compat?: PiAiCompatProfile
  /** Context capacity for a model neither the entry nor the catalog sizes. */
  defaultContextWindow: number
  /** Output capability for a model neither the entry nor the catalog sizes. */
  defaultMaxTokens: number
}

/** Report a route the deployment cannot serve, naming the settings key at fault. */
function invalid(provider: string, detail: string): never {
  throw new Error(`llm-pi-ai: provider "${provider}" ${detail}`)
}

/**
 * The one wire protocol a catalog route's shipped models agree on. This is what
 * lets a deployment add a model the installed catalog has not caught up with —
 * a provider's newest release — without restating the protocol its siblings
 * already use. A route whose shipped models disagree (an OpenAI-style catalog
 * spanning Responses and Chat Completions) has no such answer, so a model it
 * does not describe must name its protocol at the route.
 */
function sharedCatalogApi(defaults: ReadonlyMap<string, Model<Api>>): string | undefined {
  const apis = new Set<string>()
  for (const model of defaults.values()) apis.add(model.api)
  return apis.size === 1 ? [...apis][0] : undefined
}

/** The reasoning fields one materialized model carries. */
interface ModelReasoning {
  /** Whether the model reasons at all; `false` makes pi-ai ignore the map. */
  reasoning: boolean
  /** The map dispatch reads; absent only when the installed entry's (or none) applies. */
  thinkingLevelMap?: ThinkingLevelMap
}

/**
 * Resolve one model's reasoning capability from its declared efforts.
 *
 * A declared dict translates to pi-ai's `thinkingLevelMap` with every level
 * decided explicitly: declared levels carry their wire spelling, undeclared
 * levels are pinned to `null` (unsupported). Pinning matters because pi-ai's
 * own defaulting is asymmetric — an absent key means "supported" for the five
 * base levels but "unsupported" for `xhigh`/`max` — and a profile author
 * should not need to know that. A declared `off` with no value is the one
 * exception: it stays absent from the map, which pi-ai reads as "supported,
 * send nothing" — the correct dispatch where not thinking is the parameter's
 * absence — while `off` with a value sends that value.
 * @param provider - provider route key, for diagnostics.
 * @param entry - the configured model entry.
 * @param base - the installed catalog entry of the same id, when one exists.
 * @returns the reasoning fields the materialized model carries.
 */
function resolveModelReasoning(
  provider: string,
  entry: PiAiModelProfile,
  base: Model<Api> | undefined,
): ModelReasoning {
  const efforts = entry.reasoningEfforts
  if (efforts === undefined) {
    // Reasoning rides the installed entry or is absent: a bare capability flag
    // would make pi-ai advertise effort levels with no `thinkingLevelMap` to
    // spell them, and no listing endpoint reports a model's reasoning
    // protocol. The entry's map (when any) arrives through the `...base`
    // spread in the model literal.
    return { reasoning: base?.reasoning ?? false }
  }
  // The installed entry's map may ride along through `...base`; pi-ai never
  // reads it on a non-reasoning model, so stripping it is not worth a field
  // enumeration here.
  if (efforts === false) return { reasoning: false }
  // A YAML `reasoningEfforts:` left valueless arrives as null through the
  // schema union — outside the field's declared type, hence the widening —
  // while an explicit `{}` arrives as an empty dict. Both declare nothing,
  // and neither is a spelling of "inherit" or "disable".
  if ((efforts as unknown) === null || Object.keys(efforts).length === 0) {
    invalid(provider, `model "${entry.id}" has an empty reasoningEfforts; declare the offered levels, set`
      + ' false for a non-reasoning model, or omit the field to keep the installed catalog\'s capability')
  }
  const declared = THINKING_LEVELS.flatMap((level) => {
    const wire = efforts[level]
    return wire === undefined ? [] : [[level, wire] as const]
  })
  for (const [level, wire] of declared) {
    if (wire === null) {
      if (level !== 'off') {
        invalid(provider, `model "${entry.id}" reasoningEfforts.${level} needs the wire value dispatch`
          + ' should send; only "off" may leave it empty')
      }
    } else if (wire.length === 0) {
      invalid(provider, `model "${entry.id}" reasoningEfforts.${level} must not be an empty string`)
    }
  }
  if (!declared.some(([level]) => level !== 'off')) {
    invalid(provider, `model "${entry.id}" reasoningEfforts offers no level beyond "off"; declare a thinking`
      + ' level, or set reasoningEfforts to false for a non-reasoning model')
  }
  const map: ThinkingLevelMap = {}
  for (const level of THINKING_LEVELS) {
    const wire = efforts[level]
    if (wire === undefined) {
      map[level] = null
    } else if (wire !== null) {
      map[level] = wire
    }
  }
  return { reasoning: true, thinkingLevelMap: map }
}

/**
 * Resolve one model's compat block from the profile's reasoning switches.
 *
 * A model switch wins over the route switch; whatever neither sets keeps the
 * installed entry's value, and a field no layer decides falls through to
 * pi-ai's baseURL-derived detection. Only an `openai-completions` model takes
 * the switches at all: a model-level switch on any other protocol fails
 * resolution, while a route-level default skips past such models — the same
 * posture as the route-level `reasoning` default, which also must not fail
 * models it does not fit.
 * @param provider - provider route key, for diagnostics.
 * @param entry - the configured model entry.
 * @param route - the route-level switches, when any.
 * @param base - the installed catalog entry of the same id, when one exists.
 * @param api - the model's resolved wire protocol.
 * @returns a `compat` field to spread into the model, or nothing.
 */
function resolveModelCompat(
  provider: string,
  entry: PiAiModelProfile,
  route: PiAiCompatProfile | undefined,
  base: Model<Api> | undefined,
  api: string,
): { compat: OpenAICompletionsCompat } | Record<string, never> {
  const thinkingFormat = entry.compat?.thinkingFormat ?? route?.thinkingFormat
  const supportsReasoningEffort = entry.compat?.supportsReasoningEffort ?? route?.supportsReasoningEffort
  if (thinkingFormat === undefined && supportsReasoningEffort === undefined) return {}
  if (api !== 'openai-completions') {
    if (entry.compat?.thinkingFormat !== undefined || entry.compat?.supportsReasoningEffort !== undefined) {
      invalid(provider, `model "${entry.id}" sets compat reasoning switches, but its api is "${api}";`
        + ' thinkingFormat and supportsReasoningEffort exist only on openai-completions')
    }
    return {}
  }
  // The installed entry's compat matches the entry's OWN api — a route-level
  // `api` repoint (an anthropic catalog served through an OpenAI-compatible
  // gateway) leaves `base.compat` in the other protocol's shape, so it is
  // inherited only while the resolved api still is the entry's. A repointed
  // model starts from pi-ai's baseURL-derived detection instead, which is
  // what a protocol change means for every other compat field too.
  const inherited: OpenAICompletionsCompat | undefined = base?.api === api ? base.compat : undefined
  return {
    compat: {
      ...inherited,
      ...thinkingFormat === undefined ? {} : { thinkingFormat },
      ...supportsReasoningEffort === undefined ? {} : { supportsReasoningEffort },
    },
  }
}

/** One route's materialized catalog, plus the request caps its profile chose. */
export interface RouteCatalog {
  /** The materialized models in configuration order. */
  models: readonly Model<Api>[]
  /**
   * Per-request output caps this profile explicitly configured, by model id.
   *
   * Separate from `Model.maxTokens` because the two answer different
   * questions: pi-ai requires `maxTokens` as the model's output *capability*,
   * while the harness seam's `defaultMaxTokens` is a cap the deployment chose
   * to send on requests that name none. Materializing a catalog capability as
   * a request default would start capping every request at a number nobody
   * picked, so only an explicit configuration lands here.
   */
  configuredMaxTokens: ReadonlyMap<string, number>
}

/**
 * Materialize one route's catalog by merging the installed catalog defaults
 * under the configured entries. A route with no configured `models` serves the
 * installed catalog unchanged, which is what keeps an existing
 * `providers: { deepseek: { apiKeyEnv: … } }` profile working untouched.
 * @param request - the route-level catalog facts.
 * @returns the materialized models and the explicitly configured request caps.
 */
export function resolveRouteModels(request: RouteCatalogRequest): RouteCatalog {
  const { provider } = request
  const defaults = catalogModels(provider)
  const providerBaseUrl = catalogProvider(provider)?.baseUrl
  // An absent `models` key and an empty one are the same request: the config
  // schema materializes `[]` for the absent case, and an empty catalog could
  // serve no request anyway, so both mean "serve the installed catalog".
  const configured = request.models ?? []
  const overrides = request.modelOverrides ?? {}
  // Every miss is refused, never skipped: an override that lands nowhere is a
  // typo someone would otherwise hunt for in a silently unchanged model.
  for (const [id, override] of Object.entries(overrides)) {
    if (id.length === 0) invalid(provider, 'has a modelOverrides entry with an empty model id')
    if (defaults.size === 0) {
      invalid(provider, `sets modelOverrides for "${id}", but the installed catalog does not describe this route;`
        + ' a declared route spells every model out in its models list')
    }
    if (configured.length > 0) {
      invalid(provider, `sets modelOverrides for "${id}" beside a models list; models already replaces the served`
        + ' catalog, so declare the fields on its entries')
    }
    if (!defaults.has(id)) {
      invalid(provider, `modelOverrides names "${id}", which the installed catalog does not describe`)
    }
    // The id lives in the dict key; a value carrying its own would quietly
    // rename the model it meant to customize. The static shape already omits
    // it — this guards the schema boundary, which passes unknown keys through.
    if ('id' in override) {
      invalid(provider, `modelOverrides entry "${id}" sets "id", which is the dict key`)
    }
  }
  // An override becomes the catalog entry's configuration, so everything a
  // models entry may declare — capacities, efforts, compat — resolves through
  // the same path with the same diagnostics and request-default semantics.
  const entries: readonly PiAiModelProfile[] = configured.length > 0
    ? configured
    : [...defaults.values()].map(model => ({ id: model.id, ...overrides[model.id] }))
  if (entries.length === 0) {
    invalid(provider, 'resolves no models; the installed catalog does not describe this route, so its models'
      + ' must be listed in configuration')
  }
  const routeApi = sharedCatalogApi(defaults)
  const routeCompatDefined = request.compat?.thinkingFormat !== undefined
    || request.compat?.supportsReasoningEffort !== undefined
  const seen = new Set<string>()
  const configuredMaxTokens = new Map<string, number>()
  const models = entries.map((entry) => {
    if (entry.id.length === 0) invalid(provider, 'has a model with an empty id')
    if (seen.has(entry.id)) invalid(provider, `lists model "${entry.id}" more than once`)
    seen.add(entry.id)
    const base = defaults.get(entry.id)
    const api = request.api ?? base?.api ?? routeApi
    if (api === undefined) {
      invalid(provider, `model "${entry.id}" needs an api; the installed catalog does not describe it, so set the`
        + ' route\'s api to the wire protocol its endpoint speaks')
    }
    const baseUrl = request.baseURL ?? base?.baseUrl ?? providerBaseUrl
    if (baseUrl === undefined) {
      invalid(provider, `model "${entry.id}" needs a baseURL; the installed catalog does not describe this route`)
    }
    // Capacities fall back to the route's own defaults, so a model listing that
    // discloses nothing but ids still yields a serviceable route. The fallback
    // is a guess by construction, which is why it is a configurable route field
    // rather than a constant buried here.
    const contextWindow = entry.contextWindow ?? base?.contextWindow ?? request.defaultContextWindow
    if (!Number.isInteger(contextWindow) || contextWindow <= 0) {
      invalid(provider, `model "${entry.id}" contextWindow must be a positive integer`)
    }
    const maxTokens = entry.maxTokens ?? base?.maxTokens ?? request.defaultMaxTokens
    if (!Number.isInteger(maxTokens) || maxTokens <= 0) {
      invalid(provider, `model "${entry.id}" maxTokens must be a positive integer`)
    }
    // Only a value the profile named is a deployment choice; the catalog's is
    // the model's capability and stays out of request defaults.
    if (entry.maxTokens !== undefined) configuredMaxTokens.set(entry.id, entry.maxTokens)
    return {
      // The installed entry lays the floor, and the fields below override it.
      // Enumerating instead would silently drop every `Model` field this
      // package does not model — reasoning-level spellings, compatibility
      // quirks, model headers, and whatever a pi-ai upgrade adds next. Spread,
      // never enumerate.
      ...base,
      id: entry.id,
      name: entry.name ?? base?.name ?? entry.id,
      api,
      provider,
      baseUrl,
      input: base?.input ?? TEXT_ONLY,
      cost: base?.cost ?? NO_COST,
      contextWindow,
      maxTokens,
      ...resolveModelReasoning(provider, entry, base),
      ...resolveModelCompat(provider, entry, request.compat, base, api),
    }
  })
  if (routeCompatDefined && !models.some(model => model.api === 'openai-completions')) {
    invalid(provider, 'sets compat reasoning switches, but no model on the route speaks openai-completions;'
      + ' thinkingFormat and supportsReasoningEffort exist only on that protocol')
  }
  return { models, configuredMaxTokens }
}