/**
 * Model Resolver — Model and effort resolution policy
 *
 * ADR-857 rollout phase 2f: extracted from core.cts (issue #888).
 * Owns model and effort resolution policy: resolves the model, runtime tier,
 * planning granularity, reasoning effort, and fast-mode for a given agent by
 * reading project config and resolving against the model profiles and catalog.
 * Behaviour is preserved byte-for-behaviour from the prior location; only
 * the module boundary moved. The core.cjs re-export spine was retired in
 * epic #1267; callers import resolvers from model-resolver.cjs directly.
 *
 * Dependencies (leaf modules only):
 *   - node:fs / node:path (stdlib, not currently needed — included for future use)
 *   - ./config-loader.cjs    (loadConfig)
 *   - ./configuration.cjs    (CONFIG_DEFAULTS as CANONICAL_CONFIG_DEFAULTS)
 *   - ./model-profiles.cjs   (MODEL_PROFILES, AGENT_TO_PHASE_TYPE, AGENT_DEFAULT_TIERS, VALID_AGENT_TIERS, nextTier)
 *   - ./model-catalog.cjs    (MODEL_ALIAS_MAP, RUNTIME_PROFILE_MAP, PROVIDER_PRESETS)
 */

// eslint-disable-next-line @typescript-eslint/no-require-imports
import configLoaderModule = require('./config-loader.cjs');
const { loadConfig } = configLoaderModule;

// ─── Configuration Module (for CANONICAL_CONFIG_DEFAULTS used by effort/fast_mode resolvers) ─
import { CONFIG_DEFAULTS as CANONICAL_CONFIG_DEFAULTS } from './configuration.cjs';

// eslint-disable-next-line @typescript-eslint/no-require-imports
import modelProfiles = require('./model-profiles.cjs');
const { MODEL_PROFILES, AGENT_TO_PHASE_TYPE, AGENT_DEFAULT_TIERS, VALID_AGENT_TIERS, nextTier } = modelProfiles;

import { MODEL_ALIAS_MAP, RUNTIME_PROFILE_MAP, PROVIDER_PRESETS } from './model-catalog.cjs';

// ─── Model alias resolution ───────────────────────────────────────────────────

interface TierEntryResolved {
  model: string;
  reasoning_effort?: string;
  [key: string]: unknown;
}

interface ResolveTierEntryOpts {
  runtime: string | null | undefined;
  tier: string | null | undefined;
  overrides: Record<string, unknown> | null | undefined;
}

/**
 * #2517 — Resolve the runtime-aware tier entry for (runtime, tier).
 */
function resolveTierEntry({ runtime, tier, overrides }: ResolveTierEntryOpts): TierEntryResolved | null {
  if (!runtime || !tier) return null;

  const runtimeMap = RUNTIME_PROFILE_MAP as unknown as Record<string, Record<string, Record<string, unknown>>>;
  const builtin = runtimeMap[runtime]?.[tier] || null;
  const overridesMap = overrides as Record<string, Record<string, unknown>> | null | undefined;
  const userRaw = overridesMap?.[runtime]?.[tier];

  let userEntry: Record<string, unknown> | null = null;
  if (userRaw) {
    userEntry = typeof userRaw === 'string' ? { model: userRaw } : (userRaw as Record<string, unknown>);
  }

  if (!builtin && !userEntry) return null;
  return { ...(builtin || {}), ...(userEntry || {}) } as TierEntryResolved;
}

/**
 * Convenience wrapper used by resolveModelInternal.
 */
function _resolveRuntimeTier(config: Record<string, unknown>, tier: string): TierEntryResolved | null {
  return resolveTierEntry({
    runtime: config['runtime'] as string | null | undefined,
    tier,
    overrides: config['model_profile_overrides'] as Record<string, unknown> | null | undefined,
  });
}

// Reverse of the Claude tier-default IDs, plus the Fable alias which Claude
// Code's Agent tool accepts but which is not a GSD model-profile tier (#1133).
const CLAUDE_POLICY_ID_TO_ALIAS: Record<string, string> = {
  ...Object.fromEntries(
    Object.entries(MODEL_ALIAS_MAP)
      .filter((e): e is [string, string] => typeof e[1] === 'string')
      .map(([aliasName, id]) => [id, aliasName]),
  ),
  'claude-fable-5': 'fable',
};
const CLAUDE_AGENT_ALIASES = new Set(['opus', 'sonnet', 'haiku', 'fable']);

// Dedupe stderr warnings so repeated agent resolutions don't spam (#1133).
const _modelPolicyUnmappableWarned = new Set<string>();
function warnModelPolicyUnmappable(agentType: string, policyModel: string, tier: string): void {
  const key = `${agentType}::${policyModel}::${tier}`;
  if (_modelPolicyUnmappableWarned.has(key)) return;
  _modelPolicyUnmappableWarned.add(key);
  // MUST go to stderr — resolve-model's JSON result is parsed from stdout.
  process.stderr.write(
    `gsd: warning — model_policy resolved "${policyModel}" for ${agentType}, ` +
    `but it has no Claude agent alias; using "${tier}" instead.\n`,
  );
}

// Test-only: reset the model_policy warn-dedupe cache between cases (#1133).
function _resetModelPolicyWarningCacheForTests(): void {
  _modelPolicyUnmappableWarned.clear();
}

/**
 * #49 — Provider-neutral model policy preset resolution.
 */
function resolveModelPolicy(policy: Record<string, unknown> | null | undefined, tier: string | null | undefined): string | null {
  if (!policy || typeof policy !== 'object') return null;
  if (!tier) return null;

  const runtime = policy['runtime'];
  const rtOverrides = policy['runtime_tiers'];
  if (runtime && typeof runtime === 'string' && rtOverrides && typeof rtOverrides === 'object') {
    const rtOverridesMap = rtOverrides as Record<string, unknown>;
    if (Object.hasOwn(rtOverridesMap, runtime)) {
      const runtimeEntry = rtOverridesMap[runtime];
      if (runtimeEntry && typeof runtimeEntry === 'object' && Object.hasOwn(runtimeEntry, tier)) {
        const raw = (runtimeEntry as Record<string, unknown>)[tier];
        if (raw != null) {
          const entry = typeof raw === 'string' ? { model: raw } : (raw as Record<string, unknown>);
          if (entry && entry['model']) return entry['model'] as string;
        }
      }
    }
  }

  const provider = policy['provider'];
  if (!provider || typeof provider !== 'string') return null;

  if (provider === 'generic' || provider === 'custom') {
    const TIER_TO_POLICY_KEY: Record<string, string> = { opus: 'high', sonnet: 'medium', haiku: 'low' };
    const policyKey = TIER_TO_POLICY_KEY[tier];
    if (!policyKey) return null;
    const v = policy[policyKey];
    return (v && typeof v === 'string') ? v : null;
  }

  const presetsMap = PROVIDER_PRESETS as Record<string, Record<string, Record<string, { model: string } | null>>>;
  if (!Object.hasOwn(presetsMap, provider)) return null;
  const presetForProvider = presetsMap[provider];
  if (!presetForProvider || typeof presetForProvider !== 'object') return null;

  if (!Object.hasOwn(presetForProvider, tier)) return null;
  const tierPresets = presetForProvider[tier];
  if (!tierPresets || typeof tierPresets !== 'object') return null;

  const budget = (policy['budget'] && typeof policy['budget'] === 'string') ? policy['budget'] : 'medium';
  if (!Object.hasOwn(tierPresets, budget)) return null;
  const budgetEntry = tierPresets[budget];
  if (!budgetEntry || !budgetEntry.model) return null;

  return budgetEntry.model;
}

function resolveModelInternal(cwd: string, agentType: string): string {
  const config = loadConfig(cwd);

  // 1. Per-agent override
  const modelOverrides = config['model_overrides'] as Record<string, string> | null | undefined;
  const override = modelOverrides?.[agentType];
  if (override) {
    return override;
  }

  // 2. Compute the tier
  // eslint-disable-next-line @typescript-eslint/no-base-to-string
  const profile = String(config['model_profile'] || 'balanced').toLowerCase();
  const agentModels = (MODEL_PROFILES as unknown as Record<string, Record<string, string>>)[agentType];
  const phaseType = (AGENT_TO_PHASE_TYPE)[agentType];
  const configModels = config['models'] as Record<string, string> | null | undefined;
  const phaseTypeTier = (phaseType && configModels && typeof configModels === 'object')
    ? configModels[phaseType]
    : undefined;
  const VALID_TIERS = new Set(['opus', 'sonnet', 'haiku', 'inherit']);
  const tier = (phaseTypeTier && VALID_TIERS.has(phaseTypeTier))
    ? phaseTypeTier
    : (profile === 'inherit'
      ? 'inherit'
      : (agentModels ? (agentModels[profile] || agentModels['balanced']) : null));

  // 2.5. model_policy preset (#49, #1133)
  const configRuntime = config['runtime'] as string | null | undefined;
  if (tier && tier !== 'inherit') {
    const onClaude = !configRuntime || configRuntime === 'claude';
    const effectiveRuntime = configRuntime || 'claude';
    const mergedPolicy = config['model_policy']
      ? { ...(config['model_policy'] as Record<string, unknown>), runtime: effectiveRuntime }
      : null;
    const policyModel = resolveModelPolicy(mergedPolicy, tier);
    if (policyModel) {
      // Non-Claude runtimes take full model IDs verbatim (unchanged behavior).
      if (!onClaude) return policyModel;
      // Claude Code's Agent tool takes tier aliases (opus/sonnet/haiku/fable),
      // not full model IDs — map the policy-resolved ID back to an alias (#1133).
      const aliasForId = CLAUDE_POLICY_ID_TO_ALIAS[policyModel];
      if (aliasForId) return aliasForId;
      // The policy value may already be a bare Claude agent alias (e.g. "fable").
      if (CLAUDE_AGENT_ALIASES.has(policyModel)) return policyModel;
      // No Claude alias for this ID (e.g. a pinned minor version like
      // claude-opus-4-5). Warn once and fall through to the tier alias rather
      // than returning an ID Claude Code cannot spawn.
      warnModelPolicyUnmappable(agentType, policyModel, tier);
    }
  }

  // 3. Runtime-aware resolution (#2517)
  if (configRuntime && configRuntime !== 'claude' && tier && tier !== 'inherit') {
    const entry = _resolveRuntimeTier(config, tier);
    if (entry?.model) return entry.model;
  }

  // 4. resolve_model_ids: "omit"
  if (config['resolve_model_ids'] === 'omit') {
    return '';
  }

  // 5. Profile lookup (Claude-native default).
  if (!agentModels) {
    return profile === 'quality' ? 'opus'
      : profile === 'budget' ? 'haiku'
      : profile === 'inherit' ? 'inherit'
      : 'sonnet';
  }
  if (tier === 'inherit') return 'inherit';
  const alias = tier;

  if (config['resolve_model_ids']) {
    return (MODEL_ALIAS_MAP as Record<string, string>)[alias!] || alias!;
  }

  return alias!;
}

const VALID_GRANULARITIES = new Set(['coarse', 'standard', 'fine']);

/**
 * Resolve the planning granularity for a phase type (#68).
 */
function resolveGranularityInternal(cwd: string, phaseType: string | null | undefined, override?: string | null): string {
  if (override !== undefined && override !== null && override !== '') {
    if (VALID_GRANULARITIES.has(override)) {
      return override;
    }
  }
  const config = loadConfig(cwd);
  const configGranularities = config['granularities'] as Record<string, string> | null | undefined;
  const perPhase = (phaseType && configGranularities && typeof configGranularities === 'object')
    ? configGranularities[phaseType]
    : undefined;
  if (perPhase && VALID_GRANULARITIES.has(perPhase)) {
    return perPhase;
  }
  if (config['granularity'] !== undefined && config['granularity'] !== null && config['granularity'] !== '') {
    return config['granularity'] as string;
  }
  const planning = config['planning'] as Record<string, unknown> | null | undefined;
  const planningGran = planning && planning['granularity'];
  if (planningGran !== undefined && planningGran !== null && planningGran !== '') {
    return planningGran as string;
  }
  return 'standard';
}

/**
 * Validate a CLI granularity override at the command boundary. Empty/null/undefined
 * are treated as "no override" (no-op). An invalid non-empty value calls `fail`.
 */
function assertValidGranularityOverride(
  override: string | null | undefined,
  fail: (msg: string) => never,
): void {
  if (override !== undefined && override !== null && override !== '' && !VALID_GRANULARITIES.has(override)) {
    fail(`invalid granularity '${override}' (valid: ${[...VALID_GRANULARITIES].join(', ')})`);
  }
}

/**
 * #3024 — Resolve a model for a specific dynamic-routing attempt.
 */
function resolveModelForTier(cwd: string, agentType: string, attempt?: number): string {
  const config = loadConfig(cwd);
  const attemptN = Number.isInteger(attempt) && (attempt as number) > 0 ? (attempt as number) : 0;

  const modelOverrides = config['model_overrides'] as Record<string, string> | null | undefined;
  const override = modelOverrides?.[agentType];
  if (override) return override;

  if (config['model_policy'] && config['runtime'] && config['runtime'] !== 'claude') {
    return resolveModelInternal(cwd, agentType);
  }

  const dr = config['dynamic_routing'] as Record<string, unknown> | null | undefined;
  if (!dr || typeof dr !== 'object' || dr['enabled'] !== true) {
    return resolveModelInternal(cwd, agentType);
  }

  const tierModels = dr['tier_models'] as Record<string, string> | null | undefined;
  if (!tierModels || typeof tierModels !== 'object') {
    return resolveModelInternal(cwd, agentType);
  }

  const defaultTier = (AGENT_DEFAULT_TIERS)[agentType];
  if (!defaultTier || !(VALID_AGENT_TIERS).has(defaultTier)) {
    return resolveModelInternal(cwd, agentType);
  }

  const maxEscalations = Number.isInteger(dr['max_escalations']) && (dr['max_escalations'] as number) >= 0
    ? (dr['max_escalations'] as number)
    : 1;
  const escalationEnabled = dr['escalate_on_failure'] !== false;
  const effectiveAttempt = escalationEnabled
    ? Math.min(attemptN, maxEscalations)
    : 0;

  let tier = defaultTier;
  for (let i = 0; i < effectiveAttempt; i += 1) {
    const next = (nextTier)(tier);
    if (!next || next === tier) break;
    tier = next;
  }

  const alias = tierModels[tier];
  if (typeof alias !== 'string' || alias.length === 0) {
    return resolveModelInternal(cwd, agentType);
  }
  return alias;
}

// ─── #443 — Unified effort + fast_mode resolvers ─────────────────────────────

const VALID_EFFORTS = ['minimal', 'low', 'medium', 'high', 'xhigh', 'max'];
const EFFORT_SET = new Set(VALID_EFFORTS);

/**
 * Walk one step up the effort ladder from `e`.
 */
function nextEffort(e: string): string | null {
  const i = VALID_EFFORTS.indexOf(e);
  if (i < 0) return null;
  return VALID_EFFORTS[Math.min(i + 1, VALID_EFFORTS.length - 1)];
}

interface EffortOpts {
  override?: string;
}

interface FastModeOpts {
  override?: boolean;
}

/**
 * #443 — Resolve a universal effort string for (cwd, agentType).
 */
function resolveEffortInternal(cwd: string, agentType: string, opts?: EffortOpts): string {
  // Step 1: invocation override
  if (opts && typeof opts.override === 'string' && EFFORT_SET.has(opts.override)) {
    return opts.override;
  }

  const config = loadConfig(cwd);
  const effortCfg = (config['effort'] && typeof config['effort'] === 'object' && !Array.isArray(config['effort']))
    ? (config['effort'] as Record<string, unknown>)
    : null;

  // Step 2: agent_overrides
  if (effortCfg) {
    const ao = effortCfg['agent_overrides'];
    if (ao && typeof ao === 'object' && !Array.isArray(ao)) {
      const v = (ao as Record<string, unknown>)[agentType];
      if (typeof v === 'string' && EFFORT_SET.has(v)) return v;
    }
  } else {
    const canonicalEffort = (CANONICAL_CONFIG_DEFAULTS)['effort'];
    const mao = canonicalEffort && typeof canonicalEffort === 'object'
      ? (canonicalEffort as Record<string, unknown>)['agent_overrides']
      : undefined;
    if (mao && typeof mao === 'object' && !Array.isArray(mao)) {
      const v = (mao as Record<string, unknown>)[agentType];
      if (typeof v === 'string' && EFFORT_SET.has(v)) return v;
    }
  }

  // Step 3: routing_tier_defaults by agent's default tier.
  const agentTier = (AGENT_DEFAULT_TIERS)[agentType];
  if (agentTier) {
    if (effortCfg && effortCfg['routing_tier_defaults'] &&
        typeof effortCfg['routing_tier_defaults'] === 'object' &&
        !Array.isArray(effortCfg['routing_tier_defaults'])) {
      const v = (effortCfg['routing_tier_defaults'] as Record<string, unknown>)[agentTier];
      if (typeof v === 'string' && EFFORT_SET.has(v)) return v;
    } else if (!effortCfg) {
      const canonicalEffort = (CANONICAL_CONFIG_DEFAULTS)['effort'];
      const manifestDefaults = canonicalEffort && typeof canonicalEffort === 'object'
        ? (canonicalEffort as Record<string, unknown>)['routing_tier_defaults']
        : undefined;
      if (manifestDefaults && typeof manifestDefaults === 'object') {
        const v = (manifestDefaults as Record<string, unknown>)[agentTier];
        if (typeof v === 'string' && EFFORT_SET.has(v)) return v;
      }
    }
  }

  // Step 4: effort.default
  if (effortCfg) {
    const d = effortCfg['default'];
    if (typeof d === 'string' && EFFORT_SET.has(d)) return d;
  } else {
    const canonicalEffort = (CANONICAL_CONFIG_DEFAULTS)['effort'];
    const d = canonicalEffort && typeof canonicalEffort === 'object'
      ? (canonicalEffort as Record<string, unknown>)['default']
      : undefined;
    if (typeof d === 'string' && EFFORT_SET.has(d)) return d;
  }

  // Step 5: hardcoded default
  return 'high';
}

/**
 * #443 — Resolve fast_mode boolean for (cwd, agentType).
 */
function resolveFastModeInternal(cwd: string, agentType: string, opts?: FastModeOpts): boolean {
  // Step 1: invocation override
  if (opts && typeof opts.override === 'boolean') {
    return opts.override;
  }

  const config = loadConfig(cwd);
  const fmCfg = (config['fast_mode'] && typeof config['fast_mode'] === 'object' && !Array.isArray(config['fast_mode']))
    ? (config['fast_mode'] as Record<string, unknown>)
    : null;

  // Step 2: agent_overrides
  if (fmCfg) {
    const ao = fmCfg['agent_overrides'];
    if (ao && typeof ao === 'object' && !Array.isArray(ao)) {
      const v = (ao as Record<string, unknown>)[agentType];
      if (typeof v === 'boolean') return v;
    }
  }

  // Step 3: routing_tier_defaults by agent's default tier.
  const agentTier = (AGENT_DEFAULT_TIERS)[agentType];
  if (agentTier) {
    if (fmCfg && fmCfg['routing_tier_defaults'] &&
        typeof fmCfg['routing_tier_defaults'] === 'object' &&
        !Array.isArray(fmCfg['routing_tier_defaults'])) {
      const v = (fmCfg['routing_tier_defaults'] as Record<string, unknown>)[agentTier];
      if (typeof v === 'boolean') return v;
    } else if (!fmCfg) {
      const canonicalFm = (CANONICAL_CONFIG_DEFAULTS)['fast_mode'];
      const manifestDefaults = canonicalFm && typeof canonicalFm === 'object'
        ? (canonicalFm as Record<string, unknown>)['routing_tier_defaults']
        : undefined;
      if (manifestDefaults && typeof manifestDefaults === 'object') {
        const v = (manifestDefaults as Record<string, unknown>)[agentTier];
        if (typeof v === 'boolean') return v;
      }
    }
  }

  // Step 4: fast_mode.enabled
  if (fmCfg && typeof fmCfg['enabled'] === 'boolean') {
    return fmCfg['enabled'];
  }

  // Step 5: hardcoded default
  return false;
}

/**
 * #443 — Resolve effort for a dynamic-routing attempt (with escalation).
 */
function resolveEffortForTier(cwd: string, agentType: string, attempt?: number): string {
  const base = resolveEffortInternal(cwd, agentType);

  const config = loadConfig(cwd);
  const dr = config['dynamic_routing'] as Record<string, unknown> | null | undefined;
  if (!dr || typeof dr !== 'object' || dr['enabled'] !== true) {
    return base;
  }
  if (dr['escalate_on_failure'] === false) {
    return base;
  }

  const maxEscalations = Number.isInteger(dr['max_escalations']) && (dr['max_escalations'] as number) >= 0
    ? (dr['max_escalations'] as number)
    : 1;

  const attemptN = Number.isInteger(attempt) && (attempt as number) > 0 ? (attempt as number) : 0;
  const effectiveAttempt = Math.min(attemptN, maxEscalations);

  let current = base;
  for (let i = 0; i < effectiveAttempt; i++) {
    const next = nextEffort(current);
    if (!next || next === current) break;
    current = next;
  }
  return current;
}

export = {
  resolveTierEntry,
  resolveModelPolicy,
  resolveModelInternal,
  _resetModelPolicyWarningCacheForTests,
  VALID_GRANULARITIES,
  resolveGranularityInternal,
  assertValidGranularityOverride,
  resolveModelForTier,
  VALID_EFFORTS,
  EFFORT_SET,
  nextEffort,
  resolveEffortInternal,
  resolveFastModeInternal,
  resolveEffortForTier,
};