/**
 * DeterministicCompactor — the pure pipeline surface behind the `Compactor` contract
 * (ARCHITECTURE §11, saga gy5n0k.6).
 *
 * Assembles gy5n0k.1–.5 behind the three-method `Compactor` interface:
 *   - `normalize`     → gy5n0k.1 `normalize` (SessionEntry[] → NormalizedBlock[])
 *   - `buildSections` → gy5n0k.4 `buildSections` (runs the .2 extractors, plumbs ctx.codeIndex)
 *   - `formatSummary` → gy5n0k.5 `compile` (formatSummary + mergePrevious + HANDOFF_PREAMBLE)
 *
 * Pure pipeline ONLY — no `shouldCompact`. The *need* for compaction is a separate seam
 * (`CompactionTrigger`, gy5n0k.3, decision Q2): the trigger decides when/where to cut,
 * this class renders the summary for whatever front slice it's handed. Swapping a
 * `Compactor` impl never touches the trigger, and vice versa.
 *
 * The compaction orchestration (findCutPoint → normalize → buildSections → formatSummary
 * → `CompactionEntry`) lives in `AgentSession` (gy5n0k.7), NOT here — this class carries no
 * I/O, no session coupling, and no knowledge of the live window. It is a thin, deterministic
 * adapter over the free-function pipeline so a consumer can ask for "the compactor" in one
 * call and so `CompactionEntry.compactor` records `"deterministic"`.
 *
 * Unit-testable in isolation; see `tests/core/compactor/compactor.test.ts`.
 */
import type { SessionEntry } from '@/types/session-entry';
import type { NormalizedBlock } from '@/types/normalized-block';
import type { Compactor, SectionData } from '@/contracts/compactor';
import type { ExtractorContext } from '@/contracts/extractor';
import { normalize } from './normalize';
import { buildSections } from './build-sections';
import { compile } from './compile';

/**
 * Name recorded on `CompactionEntry.compactor` so a session log identifies which impl
 * produced a given summary. Stable across compactions within a session; distinct from any
 * future LLM-backed compactor's name.
 */
export const DETERMINISTIC_COMPACTOR_NAME = 'deterministic';

/**
 * Default `Compactor` impl: a thin adapter over the gy5n0k.1–.5 free-function pipeline.
 *
 * `formatSummary` delegates to `compile` (not the bare `formatSummary` free fn) so the
 * returned string is the full handoff document — preamble + merged sections + line-wrap —
 * exactly what `.7` stores on `CompactionEntry.summary` and prepends to the next turn's
 * system prompt. When `previousSummary` is omitted, `compile` emits the first-pass summary
 * (no merge); when present, it merges stable sections + re-caps volatile ones + re-strips
 * any legacy preamble baked into `prev` (gy5n0k.5).
 */
export class DeterministicCompactor implements Compactor {
  /** Recorded on `CompactionEntry.compactor`. */
  readonly name = DETERMINISTIC_COMPACTOR_NAME;

  /** Flatten the JSONL row stream; pair tool_call ↔ tool_result via a shared look-ahead index. */
  normalize(entries: SessionEntry[]): NormalizedBlock[] {
    return normalize(entries);
  }

  /** Run the .2 extractors + brief/outstanding-context (.4) over the normalized stream. */
  buildSections(blocks: NormalizedBlock[], ctx: ExtractorContext): SectionData {
    return buildSections(blocks, ctx);
  }

  /**
   * Render the section doc — `formatSummary` + `mergePrevious` + `HANDOFF_PREAMBLE` + line
   * wrap (gy5n0k.5 `compile`). The returned string is the handoff summary `.7` stores and
   * prepends; it already carries the `This summary captures work done before…` preamble.
   */
  formatSummary(sections: SectionData, previousSummary?: string): string {
    return compile(sections, previousSummary);
  }
}