/**
 * Unit tests for `finalize` (RFC #909 Ring 2 SHARED #915).
 *
 * Covers: acyclic chain · single-SCC cycle · multi-SCC · wildcard
 * expansion · re-export flattening · dynamic-unresolved passthrough ·
 * bounded fixpoint cap · module-scope binding materialization · unresolved
 * target · external target · provider `mergeBindings` precedence.
 */

import { describe, it, expect } from 'vitest';
import {
  finalize,
  type FinalizeFile,
  type FinalizeHooks,
  type ParsedImport,
  type BindingRef,
  type SymbolDefinition,
  type ScopeId,
} from 'gitnexus-shared';

// ─── Test helpers ───────────────────────────────────────────────────────────

const def = (
  nodeId: string,
  type: SymbolDefinition['type'] = 'Class',
  qualifiedName?: string,
): SymbolDefinition => ({
  nodeId,
  filePath: 'x',
  type,
  ...(qualifiedName !== undefined ? { qualifiedName } : {}),
});

const file = (
  filePath: string,
  localDefs: SymbolDefinition[] = [],
  parsedImports: ParsedImport[] = [],
): FinalizeFile => ({
  filePath,
  moduleScope: `scope:${filePath}#1:0-9999:0:Module`,
  localDefs: localDefs.map((d) => ({ ...d, filePath })),
  parsedImports,
});

/** Simple hook set: `resolveImportTarget` does a direct path lookup; wildcard
 *  expansion returns the concrete names from the target's own local defs;
 *  `mergeBindings` appends (no precedence logic). */
const defaultHooks = (files: readonly FinalizeFile[]): FinalizeHooks => ({
  resolveImportTarget(targetRaw) {
    if (targetRaw === null || targetRaw.length === 0) return null;
    return files.some((f) => f.filePath === targetRaw) ? targetRaw : null;
  },
  expandsWildcardTo(targetModuleScope) {
    const target = files.find((f) => f.moduleScope === targetModuleScope);
    if (target === undefined) return [];
    return target.localDefs.map((d) => deriveSimple(d)).filter((n): n is string => n !== null);
  },
  mergeBindings(existing, incoming) {
    return [...existing, ...incoming];
  },
});

function deriveSimple(d: SymbolDefinition): string | null {
  const q = d.qualifiedName;
  if (q === undefined || q.length === 0) return null;
  const dot = q.lastIndexOf('.');
  return dot === -1 ? q : q.slice(dot + 1);
}

const named = (localName: string, importedName: string, targetRaw: string): ParsedImport => ({
  kind: 'named',
  localName,
  importedName,
  targetRaw,
});

const aliased = (
  localName: string,
  importedName: string,
  alias: string,
  targetRaw: string,
): ParsedImport => ({ kind: 'alias', localName, importedName, alias, targetRaw });

const namespace = (localName: string, importedName: string, targetRaw: string): ParsedImport => ({
  kind: 'namespace',
  localName,
  importedName,
  targetRaw,
});

const reexport = (localName: string, importedName: string, targetRaw: string): ParsedImport => ({
  kind: 'reexport',
  localName,
  importedName,
  targetRaw,
});

const wildcard = (targetRaw: string): ParsedImport => ({ kind: 'wildcard', targetRaw });

const dynamic = (localName: string, targetRaw: string | null): ParsedImport => ({
  kind: 'dynamic-unresolved',
  localName,
  targetRaw,
});

const firstImport = (out: ReturnType<typeof finalize>, scope: ScopeId) => {
  const imports = out.imports.get(scope);
  return imports?.[0];
};

const bindingsFor = (
  out: ReturnType<typeof finalize>,
  scope: ScopeId,
  name: string,
): readonly BindingRef[] => {
  const scopeBindings = out.bindings.get(scope);
  return scopeBindings?.get(name) ?? [];
};

// ─── Tests ──────────────────────────────────────────────────────────────────

describe('finalize', () => {
  describe('trivial / acyclic', () => {
    it('handles an empty workspace', () => {
      const out = finalize({ files: [], workspaceIndex: undefined }, defaultHooks([]));
      expect(out.stats.totalFiles).toBe(0);
      expect(out.stats.totalEdges).toBe(0);
      expect(out.sccs).toEqual([]);
    });

    it('resolves a single named import across two files', () => {
      const b = file('b', [def('def:b.User', 'Class', 'b.User')]);
      const a = file('a', [], [named('User', 'User', 'b')]);
      const files = [a, b];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));

      const edge = firstImport(out, a.moduleScope)!;
      expect(edge.kind).toBe('named');
      expect(edge.targetFile).toBe('b');
      expect(edge.targetModuleScope).toBe(b.moduleScope);
      expect(edge.targetDefId).toBe('def:b.User');
      expect(edge.linkStatus).toBeUndefined();
      expect(out.stats.linkedEdges).toBe(1);
      expect(out.stats.unresolvedEdges).toBe(0);
    });

    it('marks an edge unresolved when target file cannot be resolved', () => {
      const a = file('a', [], [named('User', 'User', 'external-pkg')]);
      const out = finalize({ files: [a], workspaceIndex: undefined }, defaultHooks([a]));
      const edge = firstImport(out, a.moduleScope)!;
      expect(edge.linkStatus).toBe('unresolved');
      expect(edge.targetFile).toBeNull();
    });

    it('marks an edge unresolved when target file exists but name is not exported', () => {
      const b = file('b', [def('def:b.Other', 'Class', 'b.Other')]);
      const a = file('a', [], [named('User', 'User', 'b')]);
      const files = [a, b];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      const edge = firstImport(out, a.moduleScope)!;
      expect(edge.linkStatus).toBe('unresolved');
      // targetFile still known — unresolvability is at the name level.
      expect(edge.targetFile).toBe('b');
    });

    it('passes dynamic-unresolved edges through without linking', () => {
      const a = file('a', [], [dynamic('', 'runtime.computed')]);
      const out = finalize({ files: [a], workspaceIndex: undefined }, defaultHooks([a]));
      const edge = firstImport(out, a.moduleScope)!;
      expect(edge.kind).toBe('dynamic-unresolved');
      expect(edge.targetFile).toBeNull();
      expect(edge.linkStatus).toBeUndefined();
    });
  });

  describe('cycles + bounded fixpoint', () => {
    it('finalizes a two-file cycle (A → B → A) without hanging', () => {
      const a = file('a', [def('def:a.X', 'Class', 'a.X')], [named('Y', 'Y', 'b')]);
      const b = file('b', [def('def:b.Y', 'Class', 'b.Y')], [named('X', 'X', 'a')]);
      const files = [a, b];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));

      const aEdge = firstImport(out, a.moduleScope)!;
      const bEdge = firstImport(out, b.moduleScope)!;
      expect(aEdge.targetDefId).toBe('def:b.Y');
      expect(bEdge.targetDefId).toBe('def:a.X');
      expect(out.stats.sccCount).toBeGreaterThanOrEqual(1);
    });

    it('packs cyclic files into a single SCC with isCycle=true', () => {
      const a = file('a', [def('def:a.X', 'Class', 'a.X')], [named('Y', 'Y', 'b')]);
      const b = file('b', [def('def:b.Y', 'Class', 'b.Y')], [named('X', 'X', 'a')]);
      const files = [a, b];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      const cycles = out.sccs.filter((scc) => scc.isCycle);
      expect(cycles.length).toBe(1);
      expect(cycles[0]!.files.length).toBe(2);
      expect(new Set(cycles[0]!.files)).toEqual(new Set(['a', 'b']));
    });

    it('separates disjoint SCCs', () => {
      // a↔b cycle, c↔d cycle — disjoint.
      const a = file('a', [def('def:a.X', 'Class', 'a.X')], [named('Y', 'Y', 'b')]);
      const b = file('b', [def('def:b.Y', 'Class', 'b.Y')], [named('X', 'X', 'a')]);
      const c = file('c', [def('def:c.P', 'Class', 'c.P')], [named('Q', 'Q', 'd')]);
      const d = file('d', [def('def:d.Q', 'Class', 'd.Q')], [named('P', 'P', 'c')]);
      const files = [a, b, c, d];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      const cycleSCCs = out.sccs.filter((scc) => scc.isCycle);
      expect(cycleSCCs.length).toBe(2);
    });

    it('reports stats distinguishing linked from unresolved edges in a cycle', () => {
      const a = file(
        'a',
        [def('def:a.X', 'Class', 'a.X')],
        [named('Y', 'Y', 'b'), named('Ghost', 'Ghost', 'b')],
      );
      const b = file('b', [def('def:b.Y', 'Class', 'b.Y')], [named('X', 'X', 'a')]);
      const files = [a, b];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      expect(out.stats.linkedEdges).toBe(2); // a→b.Y and b→a.X resolve
      expect(out.stats.unresolvedEdges).toBe(1); // a→b.Ghost doesn't
    });

    it('transitions an intra-SCC edge to linkStatus=unresolved when the cap is reached', () => {
      // A↔B cycle; A imports a name that B never exports. The file-level
      // target resolves (b exists), but the name-level lookup never
      // succeeds, so the fixpoint exhausts its cap and we fall through to
      // `linkStatus: 'unresolved'` (distinct from `targetFile: null`).
      const a = file(
        'a',
        [def('def:a.X', 'Class', 'a.X')],
        [named('Ghost', 'Ghost', 'b'), named('Y', 'Y', 'b')],
      );
      const b = file('b', [def('def:b.Y', 'Class', 'b.Y')], [named('X', 'X', 'a')]);
      const files = [a, b];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));

      const aEdges = out.imports.get(a.moduleScope) ?? [];
      const ghost = aEdges.find((e) => e.localName === 'Ghost');
      expect(ghost).toBeDefined();
      // Cap-hit distinction: file target is known, but name never resolved.
      expect(ghost!.targetFile).toBe('b');
      expect(ghost!.linkStatus).toBe('unresolved');
      expect(ghost!.targetDefId).toBeUndefined();
    });
  });

  describe('wildcard expansion', () => {
    it('expands `wildcard` into one ImportEdge per exported name', () => {
      const b = file('b', [
        def('def:b.X', 'Class', 'b.X'),
        def('def:b.Y', 'Class', 'b.Y'),
        def('def:b.Z', 'Class', 'b.Z'),
      ]);
      const a = file('a', [], [wildcard('b')]);
      const files = [a, b];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      const edges = out.imports.get(a.moduleScope) ?? [];
      expect(edges.length).toBe(3);
      expect(edges.every((e) => e.kind === 'wildcard-expanded')).toBe(true);
      expect(new Set(edges.map((e) => e.localName))).toEqual(new Set(['X', 'Y', 'Z']));
      expect(new Set(edges.map((e) => e.targetDefId))).toEqual(
        new Set(['def:b.X', 'def:b.Y', 'def:b.Z']),
      );
    });

    it('leaves a wildcard unresolved when the target file cannot be resolved', () => {
      const a = file('a', [], [wildcard('external-pkg')]);
      const out = finalize({ files: [a], workspaceIndex: undefined }, defaultHooks([a]));
      const edges = out.imports.get(a.moduleScope) ?? [];
      expect(edges.length).toBe(1);
      expect(edges[0]!.linkStatus).toBe('unresolved');
    });

    it('expanded bindings land at `origin: wildcard`', () => {
      const b = file('b', [def('def:b.X', 'Class', 'b.X')]);
      const a = file('a', [], [wildcard('b')]);
      const files = [a, b];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      const bindings = bindingsFor(out, a.moduleScope, 'X');
      expect(bindings.length).toBeGreaterThanOrEqual(1);
      const imported = bindings.find((br) => br.origin === 'wildcard');
      expect(imported).toBeDefined();
      expect(imported!.def.nodeId).toBe('def:b.X');
    });
  });

  describe('re-export flattening', () => {
    it('sets transitiveVia on reexport edges', () => {
      const c = file('c', [def('def:c.X', 'Class', 'c.X')]);
      const b = file('b', [], [reexport('X', 'X', 'c')]);
      const a = file('a', [], [named('X', 'X', 'b')]);
      const files = [a, b, c];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      const reexportEdge = firstImport(out, b.moduleScope)!;
      expect(reexportEdge.kind).toBe('reexport');
      expect(reexportEdge.transitiveVia).toEqual(['c']);
    });

    it('multi-hop re-export chains only resolve when intermediate files include the name in localDefs', () => {
      // Contract (see FinalizeFile.localDefs doc): `finalize` looks up
      // `importedName` in `B.localDefs`. If B re-exports X from C but does
      // NOT include X in its own localDefs, A's import of X from B cannot
      // resolve — the fixpoint doesn't mutate localDefs across iterations.
      //
      // This test documents the current behavior: parsers that want
      // multi-hop chains to settle end-to-end must surface re-exported
      // names in the intermediate file's localDefs (with the original
      // source DefId).
      const c = file('c', [def('def:c.X', 'Class', 'c.X')]);
      // Variant 1: B does NOT include X in its own localDefs → A's import
      // fails.
      const bThin = file('b', [], [reexport('X', 'X', 'c')]);
      const aThin = file('a', [], [named('X', 'X', 'b')]);
      const thinFiles = [aThin, bThin, c];
      const thinOut = finalize(
        { files: thinFiles, workspaceIndex: undefined },
        defaultHooks(thinFiles),
      );
      expect(firstImport(thinOut, aThin.moduleScope)!.linkStatus).toBe('unresolved');

      // Variant 2: B includes X in its localDefs (re-exports surfaced) → A resolves.
      const bThick = file(
        'b',
        [def('def:c.X', 'Class', 'b.X')], // B surfaces X with its own qname
        [reexport('X', 'X', 'c')],
      );
      const aThick = file('a', [], [named('X', 'X', 'b')]);
      const thickFiles = [aThick, bThick, c];
      const thickOut = finalize(
        { files: thickFiles, workspaceIndex: undefined },
        defaultHooks(thickFiles),
      );
      expect(firstImport(thickOut, aThick.moduleScope)!.linkStatus).toBeUndefined();
      expect(firstImport(thickOut, aThick.moduleScope)!.targetDefId).toBe('def:c.X');
    });
  });

  describe('aliased + namespace imports', () => {
    it('resolves an alias under its local name while preserving targetExportedName', () => {
      const b = file('b', [def('def:b.User', 'Class', 'b.User')]);
      const a = file('a', [], [aliased('Account', 'User', 'Account', 'b')]);
      const files = [a, b];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      const edge = firstImport(out, a.moduleScope)!;
      expect(edge.kind).toBe('alias');
      expect(edge.localName).toBe('Account');
      expect(edge.targetExportedName).toBe('User');
      expect(edge.targetDefId).toBe('def:b.User');
    });

    it('records namespace imports with origin=namespace in bindings', () => {
      // Provider emits a synthetic module-representing def so the namespace
      // binding can anchor to a real SymbolDefinition.
      const numpyFile = file('numpy.py', [
        def('def:numpy', 'Namespace', 'numpy'),
        def('def:numpy.array', 'Function', 'numpy.array'),
      ]);
      const a = file('a', [], [namespace('np', 'numpy', 'numpy.py')]);
      const files = [a, numpyFile];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      const npEdge = firstImport(out, a.moduleScope)!;
      expect(npEdge.kind).toBe('namespace');
      expect(npEdge.targetModuleScope).toBe(numpyFile.moduleScope);

      const bindings = bindingsFor(out, a.moduleScope, 'np');
      expect(bindings.some((b) => b.origin === 'namespace')).toBe(true);
      expect(bindings.find((b) => b.origin === 'namespace')!.def.nodeId).toBe('def:numpy');
    });

    it('links a namespace import to the module scope even when no module-def exists', () => {
      // No synthetic def in target — the edge still resolves to the module
      // scope, just without a `targetDefId`. Bindings materialization skips
      // the binding (no def to anchor to), but the edge itself is linked.
      const numpyFile = file('numpy.py', [def('def:numpy.array', 'Function', 'numpy.array')]);
      const a = file('a', [], [namespace('np', 'numpy', 'numpy.py')]);
      const files = [a, numpyFile];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      const npEdge = firstImport(out, a.moduleScope)!;
      expect(npEdge.kind).toBe('namespace');
      expect(npEdge.linkStatus).toBeUndefined();
      expect(npEdge.targetModuleScope).toBe(numpyFile.moduleScope);
      expect(npEdge.targetDefId).toBeUndefined();
    });
  });

  describe('module-scope binding materialization', () => {
    it('lays down local defs with origin=local', () => {
      const a = file('a', [def('def:a.X', 'Class', 'a.X')]);
      const out = finalize({ files: [a], workspaceIndex: undefined }, defaultHooks([a]));
      const bindings = bindingsFor(out, a.moduleScope, 'X');
      expect(bindings.length).toBe(1);
      expect(bindings[0]!.origin).toBe('local');
      expect(bindings[0]!.def.nodeId).toBe('def:a.X');
    });

    it('layers imports on top of local defs via mergeBindings', () => {
      const b = file('b', [def('def:b.User', 'Class', 'b.User')]);
      const a = file('a', [def('def:a.User', 'Class', 'a.User')], [named('User', 'User', 'b')]);
      const files = [a, b];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      const bindings = bindingsFor(out, a.moduleScope, 'User');
      expect(bindings.length).toBe(2);
      expect(bindings.some((br) => br.origin === 'local')).toBe(true);
      expect(bindings.some((br) => br.origin === 'import')).toBe(true);
    });

    it('honors provider precedence: mergeBindings can drop existing bindings', () => {
      // Provider decides imports win over locals (Python-ish precedence).
      const b = file('b', [def('def:b.User', 'Class', 'b.User')]);
      const a = file('a', [def('def:a.User', 'Class', 'a.User')], [named('User', 'User', 'b')]);
      const files = [a, b];
      const hooks: FinalizeHooks = {
        ...defaultHooks(files),
        mergeBindings(_existing, incoming) {
          // Replace existing with incoming — last-write-wins across tiers.
          return incoming;
        },
      };
      const out = finalize({ files, workspaceIndex: undefined }, hooks);
      const bindings = bindingsFor(out, a.moduleScope, 'User');
      // Only the last merged layer (the import) remains.
      expect(bindings.length).toBe(1);
      expect(bindings[0]!.origin).toBe('import');
    });
  });

  describe('SCC-DAG exposure for parallelism', () => {
    it('returns SCCs in reverse-topological order (leaves first)', () => {
      // c ← b ← a (a imports b, b imports c, c has no imports)
      const c = file('c', [def('def:c.C', 'Class', 'c.C')]);
      const b = file('b', [def('def:b.B', 'Class', 'b.B')], [named('C', 'C', 'c')]);
      const a = file('a', [def('def:a.A', 'Class', 'a.A')], [named('B', 'B', 'b')]);
      const files = [a, b, c];
      const out = finalize({ files, workspaceIndex: undefined }, defaultHooks(files));
      // First SCC processed must be `c` (leaf), last must be `a`.
      expect(out.sccs[0]!.files[0]).toBe('c');
      expect(out.sccs[out.sccs.length - 1]!.files[0]).toBe('a');
    });
  });
});