// Decision 145: pure print-only conversion. System values are supplied by the
// existing read-only config loader; this module never reads credentials or writes.
import { checkModels, checkLimits } from "./launch.mjs";
import { requireObject, rejectUnknownKeys } from "./util.mjs";
import { refuse } from "./errors.mjs";
import { validateBusinessDocument } from "./organization-config.mjs";

export function migrateLaunch(document, mapping, file, { rolesDir, system = null }) {
  const out = structuredClone(document);
  if (!out.launch?.max) {
    validateBusinessDocument(out, file, { rolesDir });
    return out;
  }
  requireObject(mapping, "migration mapping");
  rejectUnknownKeys(mapping, ["models", "families", "selections", "instances"], "migration mapping");
  const models = checkModels(mapping.models);
  requireObject(mapping.families, "migration families");
  requireObject(out.launch.max, "old launch.max");
  for (const field of ["instances", "selections"]) {
    if (Object.hasOwn(mapping, field)) requireObject(mapping[field], `migration ${field}`);
  }
  for (const key of Object.keys(mapping.instances ?? {})) {
    if (!Object.hasOwn(out.roles, key)) refuse(`unknown migration instance ${key}`);
  }
  const limits = { models: Object.create(null) };
  const used = new Set();
  for (const [family, count] of Object.entries(out.launch.max)) {
    const key = mapping.families[family];
    if (typeof key !== "string" || !Object.hasOwn(models, key)) {
      refuse(`unknown migration mapping for family ${family}`);
    }
    const entry = models[key];
    const tuple = JSON.stringify([entry.provider, entry.model]);
    if (used.has(tuple)) refuse("ambiguous migration: two family limits map to the same provider/model");
    used.add(tuple);
    limits.models[entry.provider] ??= Object.create(null);
    limits.models[entry.provider][entry.model] = count;
  }
  const checkedLimits = checkLimits(limits);
  const previous = new Map();
  for (const [instance, role] of Object.entries(out.roles)) {
    const inherited = role.vars?.model === undefined;
    let old = role.vars?.model;
    let provider = null;
    if (inherited) {
      old = system?.["execution.model"];
      provider = system?.["execution.provider"];
      if (typeof old !== "string" || !old || typeof provider !== "string" || !provider) {
        refuse(`inherited model for ${instance} requires valid system config`);
      }
    }
    previous.set(instance, old);
    let selected = mapping.instances?.[instance] ?? mapping.selections?.[old];
    if (selected === undefined) {
      const matches = Object.entries(models).filter(([, entry]) => {
        return entry.model === old && (!inherited || entry.provider === provider);
      });
      if (matches.length !== 1) refuse(`unknown or ambiguous model mapping for ${instance}`);
      selected = matches[0][0];
    }
    if (typeof selected !== "string" || !Object.hasOwn(models, selected)) {
      refuse(`unknown or ambiguous model mapping for ${instance}`);
    }
    const entry = models[selected];
    if (entry.model !== old || (inherited && entry.provider !== provider)) {
      refuse(`migration mapping changes ${instance}'s ${inherited ? "inherited provider/model" : "external model"}`);
    }
    role.vars = { ...role.vars, model: selected };
  }
  for (const instance of [out.launch.by, ...out.launch.instances]) {
    const selected = models[out.roles[instance].vars.model];
    const old = previous.get(instance);
    const families = Object.keys(out.launch.max).filter(f => old.toLowerCase().includes(f.toLowerCase()));
    if (families.length !== 1) refuse(`unknown or ambiguous family mapping for launchable ${instance}`);
    const constrained = models[mapping.families[families[0]]];
    if (selected.provider !== constrained.provider || selected.model !== constrained.model) {
      refuse(`ambiguous migration mapping for launchable ${instance}`);
    }
  }
  for (const family of Object.keys(out.launch.max)) {
    const entry = models[mapping.families[family]];
    for (const [instance, old] of previous) {
      if (!old.toLowerCase().includes(family.toLowerCase())) continue;
      const actual = models[out.roles[instance].vars.model];
      if (old !== entry.model || actual.provider !== entry.provider) {
        refuse(`ambiguous migration: family ${family} spans multiple provider/model pairs`);
      }
    }
  }
  const { max, ...launch } = out.launch;
  out.launch = { ...launch, models, limits: checkedLimits };
  validateBusinessDocument(out, file, { rolesDir });
  return out;
}