import type { PromptVariant } from "./summarizer";

/**
 * Small-context clamping: on a small-context model, the configured
 * verbatim/chunk/reserve/summary sizes can each exceed what the window can
 * hold at all — e.g. keepRecentTokens 6000 on a 4k window leaves no room
 * for compaction to ever cut, right where it's needed most. Each field is
 * capped to max(floor, ctx * fraction) of the real context length; the
 * effective value only ever reduces a configured one, never raises it.
 */
export interface SizeConfig {
  contextLength: number | undefined;
  keepRecentTokens: number;
  chunkTokens: number;
  reservedOutputTokens: number;
  summarizerMaxTokens: number;
}

export interface EffectiveSizes {
  keepRecentTokens: number;
  chunkTokens: number;
  reservedOutputTokens: number;
  summarizerMaxTokens: number;
  /** Names of fields that were reduced, for the one-time warning. */
  clamped: string[];
}

export function effectiveSizes(cfg: SizeConfig): EffectiveSizes {
  const ctx = cfg.contextLength;
  if (ctx === undefined || ctx <= 0) {
    return {
      keepRecentTokens: cfg.keepRecentTokens,
      chunkTokens: cfg.chunkTokens,
      reservedOutputTokens: cfg.reservedOutputTokens,
      summarizerMaxTokens: cfg.summarizerMaxTokens,
      clamped: [],
    };
  }
  const clamped: string[] = [];
  const clamp = (
    name: string,
    configured: number,
    floor: number,
    fraction: number,
  ): number => {
    const cap = Math.max(floor, Math.floor(ctx * fraction));
    if (configured > cap) {
      clamped.push(name);
      return cap;
    }
    return configured;
  };
  const keepRecentTokens = clamp(
    "keepRecentTokens",
    cfg.keepRecentTokens,
    512,
    0.25,
  );
  const chunkTokens = clamp("chunkTokens", cfg.chunkTokens, 1024, 0.3);
  const reservedOutputTokens = clamp(
    "reservedOutputTokens",
    cfg.reservedOutputTokens,
    256,
    0.25,
  );
  const summarizerMaxTokens = clamp(
    "summarizerMaxTokens",
    cfg.summarizerMaxTokens,
    200,
    0.15,
  );
  return {
    keepRecentTokens,
    chunkTokens,
    reservedOutputTokens,
    summarizerMaxTokens,
    clamped,
  };
}

/**
 * Which summarizer system-prompt variant to use this turn. Forced modes
 * ("full"/"compact") always win; "auto" always resolves to "full" — bench
 * 2026-08-24: full beat compact on recall at 3B and 18B; auto stays full —
 * compact remains the rescue prompt and a manual option.
 */
export function pickPromptVariant(
  mode: "auto" | "full" | "compact",
): PromptVariant {
  if (mode !== "auto") return mode;
  return "full";
}

import type { PromptVariant } from "./summarizer";

/**
 * Small-context clamping: on a small-context model, the configured
 * verbatim/chunk/reserve/summary sizes can each exceed what the window can
 * hold at all — e.g. keepRecentTokens 6000 on a 4k window leaves no room
 * for compaction to ever cut, right where it's needed most. Each field is
 * capped to max(floor, ctx * fraction) of the real context length; the
 * effective value only ever reduces a configured one, never raises it.
 */
export interface SizeConfig {
  contextLength: number | undefined;
  keepRecentTokens: number;
  chunkTokens: number;
  reservedOutputTokens: number;
  summarizerMaxTokens: number;
}

export interface EffectiveSizes {
  keepRecentTokens: number;
  chunkTokens: number;
  reservedOutputTokens: number;
  summarizerMaxTokens: number;
  /** Names of fields that were reduced, for the one-time warning. */
  clamped: string[];
}

export function effectiveSizes(cfg: SizeConfig): EffectiveSizes {
  const ctx = cfg.contextLength;
  if (ctx === undefined || ctx <= 0) {
    return {
      keepRecentTokens: cfg.keepRecentTokens,
      chunkTokens: cfg.chunkTokens,
      reservedOutputTokens: cfg.reservedOutputTokens,
      summarizerMaxTokens: cfg.summarizerMaxTokens,
      clamped: [],
    };
  }
  const clamped: string[] = [];
  const clamp = (
    name: string,
    configured: number,
    floor: number,
    fraction: number,
  ): number => {
    const cap = Math.max(floor, Math.floor(ctx * fraction));
    if (configured > cap) {
      clamped.push(name);
      return cap;
    }
    return configured;
  };
  const keepRecentTokens = clamp(
    "keepRecentTokens",
    cfg.keepRecentTokens,
    512,
    0.25,
  );
  const chunkTokens = clamp("chunkTokens", cfg.chunkTokens, 1024, 0.3);
  const reservedOutputTokens = clamp(
    "reservedOutputTokens",
    cfg.reservedOutputTokens,
    256,
    0.25,
  );
  const summarizerMaxTokens = clamp(
    "summarizerMaxTokens",
    cfg.summarizerMaxTokens,
    200,
    0.15,
  );
  return {
    keepRecentTokens,
    chunkTokens,
    reservedOutputTokens,
    summarizerMaxTokens,
    clamped,
  };
}

/**
 * Which summarizer system-prompt variant to use this turn. Forced modes
 * ("full"/"compact") always win; "auto" always resolves to "full" — bench
 * 2026-08-24: full beat compact on recall at 3B and 18B; auto stays full —
 * compact remains the rescue prompt and a manual option.
 */
export function pickPromptVariant(
  mode: "auto" | "full" | "compact",
): PromptVariant {
  if (mode !== "auto") return mode;
  return "full";
}