/**
 * proposalModel — pure helpers over the F4 `proposals[]` section (spec §6.3,
 * INV-13: pending-only). Mirrors threadModel.ts: vscode-free mutations against
 * an Artifact, used inside CoauthorStore.update() by ProposalController.
 * The diff body is PRESENTATION ONLY — the truth is fingerprint.text →
 * replacement (INV-11); a whole-range -/+ rendering, not an LCS diff (§6.7).
 */
import { newId, type Artifact, type Fingerprint, type Proposal, type Provenance } from "./model";

export function addProposal(
  artifact: Artifact,
  fp: Fingerprint,
  replacement: string,
  author: Provenance,
  opts?: { turnId?: string; instruction?: string; granularity?: "block" | "single" },
): { proposalId: string; anchorId: string } {
  const anchorId = newId("a");
  const proposalId = newId("pr");
  artifact.anchors[anchorId] = { fingerprint: fp };
  artifact.proposals.push({
    id: proposalId,
    anchorId,
    replacement,
    author,
    createdAt: new Date().toISOString(),
    ...(opts?.turnId !== undefined ? { turnId: opts.turnId } : {}),
    ...(opts?.instruction !== undefined ? { instruction: opts.instruction } : {}),
    ...(opts?.granularity !== undefined ? { granularity: opts.granularity } : {}),
  });
  return { proposalId, anchorId };
}

/** Remove a pending proposal (accept and reject both end here — INV-13). */
export function removeProposal(artifact: Artifact, proposalId: string): boolean {
  const before = artifact.proposals.length;
  artifact.proposals = artifact.proposals.filter((p) => p.id !== proposalId);
  return artifact.proposals.length < before;
}

/**
 * F12/#64 (INV-48): record a proposal as optimistically applied — store the
 * pre-apply `original` (for revert + the struck `<del>`) and re-point its anchor
 * fingerprint to the now-in-buffer applied text so `resolve()` finds it. Idempotent
 * shape: a second call simply overwrites with the same values.
 */
export function setProposalApplied(
  artifact: Artifact,
  proposalId: string,
  appliedFp: Fingerprint,
  original: string,
): boolean {
  const p = artifact.proposals.find((x) => x.id === proposalId);
  if (!p) return false;
  p.original = original;
  artifact.anchors[p.anchorId] = { fingerprint: appliedFp };
  return true;
}

/** Markdown comment body: instruction header + fenced whole-range diff. */
export function proposalBody(targetText: string, p: Proposal): string {
  const header = p.instruction ? `**Claude proposes** — _${p.instruction}_` : "**Claude proposes**";
  const diffLines = [
    ...targetText.split("\n").map((l) => `- ${l}`),
    ...p.replacement.split("\n").map((l) => `+ ${l}`),
  ].join("\n");
  return `${header}\n\n\`\`\`diff\n${diffLines}\n\`\`\`\n\n✓ Accept applies this replacement · ✗ Reject discards it`;
}