// Changes to a ledger, shared by the model's tools and the user's commands. Each returns a
// short description of what changed, or throws an OpError with a message for the caller.

import { Actor, commit, currentStep, Finding, Ledger, LedgerEvent, listVersions, loadMeta, progress, readEvents, saveMeta, Step, StepStatus, Verification } from "./ledger";
import { clip, oneLine } from "./text";

export class OpError extends Error {}

const MAX_TEXT = 1200;

function clean(text: string | undefined, what: string): string {
  const t = (text ?? "").trim();
  if (!t) throw new OpError(`${what} is empty.`);
  if (t.length > MAX_TEXT) throw new OpError(`${what} is longer than ${MAX_TEXT} characters; record the essential part.`);
  return t;
}

// Project state, not facts about the user: those belong in the user's memory.
const ABOUT_USER = /\b(the user|user's|the user’s)\b/i;
const PERSONAL = /\b(lives?|living|born|birthday|age|girlfriend|boyfriend|wife|husband|partner|family|health|diagnos\w*|medication|salary|income|religio\w*|address|phone number|likes|loves|hates|favou?rite)\b/i;
export function looksPersonal(text: string): boolean {
  return ABOUT_USER.test(text) && PERSONAL.test(text);
}

export function initialVerification(source: string): Verification {
  return /^user$/i.test(source.trim()) ? "verified" : "unverified";
}

export function addSteps(l: Ledger, texts: string[], status: StepStatus, actor: Actor, chat?: string): string {
  if (!texts.length) throw new OpError("No step text given.");
  const added: Step[] = [];
  for (const raw of texts) {
    const text = clean(raw, "Step text");
    const step: Step = { id: (l.plan.at(-1)?.id ?? 0) + 1, text, status: added.length === 0 ? status : "todo", note: "" };
    l.plan.push(step);
    added.push(step);
  }
  commit(l, added.map((s) => ({ actor, op: "step_added", id: String(s.id), text: s.text, chat })));
  return added.length === 1 ? `step ${added[0].id} added` : `steps ${added[0].id} to ${added.at(-1)!.id} added`;
}

export function updateStep(
  l: Ledger,
  id: number,
  change: { status?: StepStatus; note?: string; text?: string },
  actor: Actor,
  chat?: string,
): string {
  const step = l.plan.find((s) => s.id === id);
  if (!step) throw new OpError(`There is no step ${id}. Steps are numbered 1 to ${l.plan.length}.`);
  if (change.status === undefined && change.note === undefined && change.text === undefined) {
    throw new OpError("Nothing to change: give a status, a note or new text.");
  }
  const parts: string[] = [];
  if (change.text !== undefined) { step.text = clean(change.text, "Step text"); parts.push("reworded"); }
  if (change.note !== undefined) { step.note = oneLine(change.note).slice(0, 300); parts.push("note set"); }
  if (change.status !== undefined && change.status !== step.status) { step.status = change.status; parts.push(`now ${change.status}`); }
  commit(l, [{ actor, op: "step_updated", id: String(id), text: parts.join(", ") || "unchanged", chat }]);
  return `step ${id} ${parts.join(", ") || "unchanged"}`;
}

export function addFinding(l: Ledger, text: string, source: string | undefined, actor: Actor, chat?: string): string {
  const t = clean(text, "Finding");
  if (looksPersonal(t)) throw new OpError("This reads like a personal fact about the user. Facts about the user belong in the user's memory, not in a project ledger.");
  const src = oneLine(source ?? "").slice(0, 300) || "none";
  const f: Finding = {
    id: `F${++l.counters.F}`,
    text: t,
    source: src,
    verification: src === "none" ? "unverified" : initialVerification(src),
    step: currentStep(l)?.id,
    chat,
    at: new Date().toISOString(),
  };
  l.findings.push(f);
  commit(l, [{ actor, op: "finding_added", id: f.id, text: t, chat }]);
  return `${f.id} added: ${clip(t, 160)} (source: ${clip(src, 80)})`;
}

export function addDecision(l: Ledger, text: string, reason: string | undefined, actor: Actor, chat?: string): string {
  const t = clean(text, "Decision");
  if (looksPersonal(t)) throw new OpError("This reads like a personal fact about the user. Facts about the user belong in the user's memory, not in a project ledger.");
  const id = `D${++l.counters.D}`;
  l.decisions.push({ id, text: t, reason: oneLine(reason ?? "").slice(0, 400), by: actor, step: currentStep(l)?.id, at: new Date().toISOString() });
  commit(l, [{ actor, op: "decision_added", id, text: t, chat }]);
  return `${id} added: ${clip(t, 160)}`;
}

export function addQuestion(l: Ledger, text: string, actor: Actor, chat?: string): string {
  const t = clean(text, "Question");
  const id = `Q${++l.counters.Q}`;
  l.questions.push({ id, text: t, status: "open", turn: loadMeta(l.name).turns, at: new Date().toISOString() });
  commit(l, [{ actor, op: "question_added", id, text: t, chat }]);
  return `${id} opened: ${clip(t, 160)}`;
}

export function resolveQuestion(
  l: Ledger,
  ref: string,
  answer: string,
  asFinding: { source?: string } | null,
  actor: Actor,
  chat?: string,
): string {
  const id = /^\d+$/.test(ref.trim()) ? `Q${ref.trim()}` : ref.trim().toUpperCase();
  const q = l.questions.find((x) => x.id === id);
  if (!q) throw new OpError(`There is no question ${id}.`);
  if (q.status === "resolved") throw new OpError(`${id} is already resolved.`);
  q.status = "resolved";
  q.answer = clean(answer, "Answer");
  q.resolvedAt = new Date().toISOString();
  commit(l, [{ actor, op: "question_resolved", id, text: q.answer, chat }]);
  let msg = `${id} resolved`;
  if (asFinding) msg += `; ${addFinding(l, `${q.text} ${q.answer}`, asFinding.source, actor, chat)}`;
  return msg;
}

export function setGoal(l: Ledger, goal: string, chat?: string): string {
  l.goal = clean(goal, "Goal");
  l.goalSource = "command";
  commit(l, [{ actor: "user", op: "goal_set", text: l.goal, chat }]);
  return "goal set";
}

export function addConstraint(l: Ledger, text: string, chat?: string): string {
  const t = clean(text, "Constraint");
  l.constraints.push(t);
  commit(l, [{ actor: "user", op: "constraint_added", text: t, chat }]);
  return `constraint ${l.constraints.length} added`;
}

// The guidance line every tool result ends with.
export function nextLine(l: Ledger): string {
  const p = progress(l);
  if (!p.total) return "next: Break the goal into a few steps with ledger_plan, then mark the first one doing.";
  const cur = currentStep(l);
  if (cur) return "next: Continue with the current step. Record findings and decisions as you establish them, and mark the step done when it is.";
  if (p.done === p.total) return "next: All steps are done. Give the user the result and stop. Add steps beyond the goal only if the user asks.";
  return "next: Mark the next step doing with ledger_plan before working on it.";
}

// Changes that are part of the project's structure rather than its content, and are not undone.
const NOT_UNDOABLE = new Set(["project_created", "chat_bound", "chat_unbound", "chat_deleted", "project_renamed", "sources_checked", "undo"]);

function describeEvent(e: LedgerEvent): string {
  switch (e.op) {
    case "finding_added": case "decision_added": return `${e.id} added`;
    case "question_added": return `${e.id} opened`;
    case "question_resolved": return `${e.id} resolved`;
    case "step_added": return `step ${e.id} added`;
    case "step_updated": return `step ${e.id} ${e.text ?? "updated"}`;
    case "goal_set": return "the goal change";
    case "constraint_added": return "the added constraint";
    case "hand_edit": return `the hand edit (${e.text ?? "changes"})`;
    default: return e.op.replace(/_/g, " ");
  }
}

// Steps the ledger back one change at a time: each call restores the state from before the
// most recent change by the user or the model that has not been undone yet. The project's name
// and chat bindings stay as they are, and ids already used are not handed out again.
export function undoLast(l: Ledger, chat?: string): string {
  const meta = loadMeta(l.name);
  const limit = meta.undoneTo ?? l.seq;
  const events = readEvents(l.name, 0);
  for (const v of listVersions(l.name)) {
    if (v.seq >= limit) continue;
    const first = events.find((e) => e.seq === v.seq + 1);
    if (!first || first.actor === "plugin" || NOT_UNDOABLE.has(first.op)) continue;
    const reverted = events.filter((e) => e.seq > v.seq && e.seq <= limit && !NOT_UNDOABLE.has(e.op) && e.actor !== "plugin");
    const what = reverted.length ? reverted.map(describeEvent).join(", ") : describeEvent(first);
    const restored: Ledger = {
      ...v,
      name: l.name,
      chats: l.chats,
      seq: l.seq,
      counters: { F: Math.max(v.counters.F, l.counters.F), D: Math.max(v.counters.D, l.counters.D), Q: Math.max(v.counters.Q, l.counters.Q) },
    };
    commit(restored, [{ actor: "user", op: "undo", text: `undid ${what}`, chat }]);
    const after = loadMeta(l.name);
    after.undoneTo = v.seq;
    saveMeta(l.name, after);
    return `Undid ${what}.`;
  }
  throw new OpError("There is nothing earlier to undo.");
}

// Changes to a ledger, shared by the model's tools and the user's commands. Each returns a
// short description of what changed, or throws an OpError with a message for the caller.

import { Actor, commit, currentStep, Finding, Ledger, LedgerEvent, listVersions, loadMeta, progress, readEvents, saveMeta, Step, StepStatus, Verification } from "./ledger";
import { clip, oneLine } from "./text";

export class OpError extends Error {}

const MAX_TEXT = 1200;

function clean(text: string | undefined, what: string): string {
  const t = (text ?? "").trim();
  if (!t) throw new OpError(`${what} is empty.`);
  if (t.length > MAX_TEXT) throw new OpError(`${what} is longer than ${MAX_TEXT} characters; record the essential part.`);
  return t;
}

// Project state, not facts about the user: those belong in the user's memory.
const ABOUT_USER = /\b(the user|user's|the user’s)\b/i;
const PERSONAL = /\b(lives?|living|born|birthday|age|girlfriend|boyfriend|wife|husband|partner|family|health|diagnos\w*|medication|salary|income|religio\w*|address|phone number|likes|loves|hates|favou?rite)\b/i;
export function looksPersonal(text: string): boolean {
  return ABOUT_USER.test(text) && PERSONAL.test(text);
}

export function initialVerification(source: string): Verification {
  return /^user$/i.test(source.trim()) ? "verified" : "unverified";
}

export function addSteps(l: Ledger, texts: string[], status: StepStatus, actor: Actor, chat?: string): string {
  if (!texts.length) throw new OpError("No step text given.");
  const added: Step[] = [];
  for (const raw of texts) {
    const text = clean(raw, "Step text");
    const step: Step = { id: (l.plan.at(-1)?.id ?? 0) + 1, text, status: added.length === 0 ? status : "todo", note: "" };
    l.plan.push(step);
    added.push(step);
  }
  commit(l, added.map((s) => ({ actor, op: "step_added", id: String(s.id), text: s.text, chat })));
  return added.length === 1 ? `step ${added[0].id} added` : `steps ${added[0].id} to ${added.at(-1)!.id} added`;
}

export function updateStep(
  l: Ledger,
  id: number,
  change: { status?: StepStatus; note?: string; text?: string },
  actor: Actor,
  chat?: string,
): string {
  const step = l.plan.find((s) => s.id === id);
  if (!step) throw new OpError(`There is no step ${id}. Steps are numbered 1 to ${l.plan.length}.`);
  if (change.status === undefined && change.note === undefined && change.text === undefined) {
    throw new OpError("Nothing to change: give a status, a note or new text.");
  }
  const parts: string[] = [];
  if (change.text !== undefined) { step.text = clean(change.text, "Step text"); parts.push("reworded"); }
  if (change.note !== undefined) { step.note = oneLine(change.note).slice(0, 300); parts.push("note set"); }
  if (change.status !== undefined && change.status !== step.status) { step.status = change.status; parts.push(`now ${change.status}`); }
  commit(l, [{ actor, op: "step_updated", id: String(id), text: parts.join(", ") || "unchanged", chat }]);
  return `step ${id} ${parts.join(", ") || "unchanged"}`;
}

export function addFinding(l: Ledger, text: string, source: string | undefined, actor: Actor, chat?: string): string {
  const t = clean(text, "Finding");
  if (looksPersonal(t)) throw new OpError("This reads like a personal fact about the user. Facts about the user belong in the user's memory, not in a project ledger.");
  const src = oneLine(source ?? "").slice(0, 300) || "none";
  const f: Finding = {
    id: `F${++l.counters.F}`,
    text: t,
    source: src,
    verification: src === "none" ? "unverified" : initialVerification(src),
    step: currentStep(l)?.id,
    chat,
    at: new Date().toISOString(),
  };
  l.findings.push(f);
  commit(l, [{ actor, op: "finding_added", id: f.id, text: t, chat }]);
  return `${f.id} added: ${clip(t, 160)} (source: ${clip(src, 80)})`;
}

export function addDecision(l: Ledger, text: string, reason: string | undefined, actor: Actor, chat?: string): string {
  const t = clean(text, "Decision");
  if (looksPersonal(t)) throw new OpError("This reads like a personal fact about the user. Facts about the user belong in the user's memory, not in a project ledger.");
  const id = `D${++l.counters.D}`;
  l.decisions.push({ id, text: t, reason: oneLine(reason ?? "").slice(0, 400), by: actor, step: currentStep(l)?.id, at: new Date().toISOString() });
  commit(l, [{ actor, op: "decision_added", id, text: t, chat }]);
  return `${id} added: ${clip(t, 160)}`;
}

export function addQuestion(l: Ledger, text: string, actor: Actor, chat?: string): string {
  const t = clean(text, "Question");
  const id = `Q${++l.counters.Q}`;
  l.questions.push({ id, text: t, status: "open", turn: loadMeta(l.name).turns, at: new Date().toISOString() });
  commit(l, [{ actor, op: "question_added", id, text: t, chat }]);
  return `${id} opened: ${clip(t, 160)}`;
}

export function resolveQuestion(
  l: Ledger,
  ref: string,
  answer: string,
  asFinding: { source?: string } | null,
  actor: Actor,
  chat?: string,
): string {
  const id = /^\d+$/.test(ref.trim()) ? `Q${ref.trim()}` : ref.trim().toUpperCase();
  const q = l.questions.find((x) => x.id === id);
  if (!q) throw new OpError(`There is no question ${id}.`);
  if (q.status === "resolved") throw new OpError(`${id} is already resolved.`);
  q.status = "resolved";
  q.answer = clean(answer, "Answer");
  q.resolvedAt = new Date().toISOString();
  commit(l, [{ actor, op: "question_resolved", id, text: q.answer, chat }]);
  let msg = `${id} resolved`;
  if (asFinding) msg += `; ${addFinding(l, `${q.text} ${q.answer}`, asFinding.source, actor, chat)}`;
  return msg;
}

export function setGoal(l: Ledger, goal: string, chat?: string): string {
  l.goal = clean(goal, "Goal");
  l.goalSource = "command";
  commit(l, [{ actor: "user", op: "goal_set", text: l.goal, chat }]);
  return "goal set";
}

export function addConstraint(l: Ledger, text: string, chat?: string): string {
  const t = clean(text, "Constraint");
  l.constraints.push(t);
  commit(l, [{ actor: "user", op: "constraint_added", text: t, chat }]);
  return `constraint ${l.constraints.length} added`;
}

// The guidance line every tool result ends with.
export function nextLine(l: Ledger): string {
  const p = progress(l);
  if (!p.total) return "next: Break the goal into a few steps with ledger_plan, then mark the first one doing.";
  const cur = currentStep(l);
  if (cur) return "next: Continue with the current step. Record findings and decisions as you establish them, and mark the step done when it is.";
  if (p.done === p.total) return "next: All steps are done. Give the user the result and stop. Add steps beyond the goal only if the user asks.";
  return "next: Mark the next step doing with ledger_plan before working on it.";
}

// Changes that are part of the project's structure rather than its content, and are not undone.
const NOT_UNDOABLE = new Set(["project_created", "chat_bound", "chat_unbound", "chat_deleted", "project_renamed", "sources_checked", "undo"]);

function describeEvent(e: LedgerEvent): string {
  switch (e.op) {
    case "finding_added": case "decision_added": return `${e.id} added`;
    case "question_added": return `${e.id} opened`;
    case "question_resolved": return `${e.id} resolved`;
    case "step_added": return `step ${e.id} added`;
    case "step_updated": return `step ${e.id} ${e.text ?? "updated"}`;
    case "goal_set": return "the goal change";
    case "constraint_added": return "the added constraint";
    case "hand_edit": return `the hand edit (${e.text ?? "changes"})`;
    default: return e.op.replace(/_/g, " ");
  }
}

// Steps the ledger back one change at a time: each call restores the state from before the
// most recent change by the user or the model that has not been undone yet. The project's name
// and chat bindings stay as they are, and ids already used are not handed out again.
export function undoLast(l: Ledger, chat?: string): string {
  const meta = loadMeta(l.name);
  const limit = meta.undoneTo ?? l.seq;
  const events = readEvents(l.name, 0);
  for (const v of listVersions(l.name)) {
    if (v.seq >= limit) continue;
    const first = events.find((e) => e.seq === v.seq + 1);
    if (!first || first.actor === "plugin" || NOT_UNDOABLE.has(first.op)) continue;
    const reverted = events.filter((e) => e.seq > v.seq && e.seq <= limit && !NOT_UNDOABLE.has(e.op) && e.actor !== "plugin");
    const what = reverted.length ? reverted.map(describeEvent).join(", ") : describeEvent(first);
    const restored: Ledger = {
      ...v,
      name: l.name,
      chats: l.chats,
      seq: l.seq,
      counters: { F: Math.max(v.counters.F, l.counters.F), D: Math.max(v.counters.D, l.counters.D), Q: Math.max(v.counters.Q, l.counters.Q) },
    };
    commit(restored, [{ actor: "user", op: "undo", text: `undid ${what}`, chat }]);
    const after = loadMeta(l.name);
    after.undoneTo = v.seq;
    saveMeta(l.name, after);
    return `Undid ${what}.`;
  }
  throw new OpError("There is nothing earlier to undo.");
}