package intent

import (
	"errors"
	"testing"
	"testing/fstest"
)

func mapFS(files map[string]string) fstest.MapFS {
	m := make(fstest.MapFS, len(files))
	for k, v := range files {
		m[k] = &fstest.MapFile{Data: []byte(v)}
	}
	return m
}

const overlayAddJSON = `{
  "intents": [
    {"id": "demo.misc.added", "domain": "demo", "version": 1, "matcher": {"includes_any": ["新增"]}}
  ]
}`

func TestLoadOverlaysOrderAndSources(t *testing.T) {
	fsys := mapFS(map[string]string{
		"specs/a.json": overlayAddJSON,
		"specs/b.json": `{"disable": ["demo.misc.added"]}`,
	})
	entries, err := loadOverlays(fsys, []string{"specs"})
	if err != nil {
		t.Fatalf("load: %v", err)
	}
	if len(entries) != 2 {
		t.Fatalf("expected 2 entries, got %d", len(entries))
	}
	if entries[0].spec.ID != "demo.misc.added" || entries[0].source != "specs/a.json#intents[0]" {
		t.Fatalf("entry0 mismatch: %+v", entries[0])
	}
	if !entries[1].disable || entries[1].id != "demo.misc.added" || entries[1].source != "specs/b.json#disable[0]" {
		t.Fatalf("entry1 mismatch: %+v", entries[1])
	}
}

func TestLoadOverlaysFileOrder(t *testing.T) {
	// 同目录按文件名字典序：a.json 先应用，b.json 后应用。
	fsys := mapFS(map[string]string{
		"specs/a.json": `{"intents": [{"id": "demo.x.one", "domain": "demo", "version": 1, "matcher": {"includes_any": ["a"]}}]}`,
		"specs/b.json": `{"intents": [{"id": "demo.x.one", "domain": "demo", "version": 2, "matcher": {"includes_any": ["b"]}}]}`,
	})
	entries, err := loadOverlays(fsys, []string{"specs"})
	if err != nil {
		t.Fatalf("load: %v", err)
	}
	if len(entries) != 2 || entries[0].spec.Version != 1 || entries[1].spec.Version != 2 {
		t.Fatalf("file order not applied: %+v", entries)
	}
}

func TestLoadOverlaysUnknownField(t *testing.T) {
	fsys := mapFS(map[string]string{
		"specs/bad.json": `{"intents": [{"id": "demo.x.one", "domain": "demo", "version": 1, "matcher": {"includes_any": ["a"]}, "unknown_key": 1}]}`,
	})
	_, err := loadOverlays(fsys, []string{"specs"})
	var e *Error
	if !errors.As(err, &e) || e.Code != InvalidSpec {
		t.Fatalf("expected intent.invalid_spec, got %v", err)
	}
	if e.Fields["file"] != "specs/bad.json" {
		t.Fatalf("error missing file source: %v", e.Fields)
	}
}

func TestLoadOverlaysBadJSON(t *testing.T) {
	fsys := mapFS(map[string]string{"specs/broken.json": `{"intents": [}`})
	_, err := loadOverlays(fsys, []string{"specs"})
	var e *Error
	if !errors.As(err, &e) || e.Code != InvalidSpec {
		t.Fatalf("expected intent.invalid_spec for broken json, got %v", err)
	}
}

func TestLoadOverlaysMissingRoot(t *testing.T) {
	fsys := mapFS(map[string]string{})
	_, err := loadOverlays(fsys, []string{"specs"})
	var e *Error
	if !errors.As(err, &e) || e.Code != LoadFailed {
		t.Fatalf("expected intent.load_failed, got %v", err)
	}
	if e.Fields["root"] != "specs" {
		t.Fatalf("error missing root: %v", e.Fields)
	}
}

func TestLoadOverlaysSingleFileRoot(t *testing.T) {
	fsys := mapFS(map[string]string{"single.json": overlayAddJSON})
	entries, err := loadOverlays(fsys, []string{"single.json"})
	if err != nil {
		t.Fatalf("load: %v", err)
	}
	if len(entries) != 1 || entries[0].source != "single.json#intents[0]" {
		t.Fatalf("single file root mismatch: %+v", entries)
	}
}