package config

import (
	"fmt"
	"maps"
	"reflect"
	"strings"
	"testing"
)

// Kinds that LoadFromViper knows how to read.
var viperKinds = map[reflect.Kind]bool{
	reflect.String: true,
	reflect.Int:    true,
	reflect.Bool:   true,
	reflect.Slice:  true,
}

// Every key round-trips through TypeOf/ValueOf/SetValue and has a type that
// LoadFromViper can read.
func TestKeysRoundTrip(t *testing.T) {
	var conf JobSearchConfig
	if err := applyDefaults(&conf); err != nil {
		t.Fatalf("defaults: %v", err)
	}
	for key, want := range conf.Flatten() {
		kind, err := conf.TypeOf(key)
		if err != nil {
			t.Errorf("TypeOf(%q): %v", key, err)
		} else if !viperKinds[kind] {
			t.Errorf(
				"TypeOf(%q) = %v, which LoadFromViper does not handle", key, kind,
			)
		}
		got, err := conf.ValueOf(key)
		if err != nil || !reflect.DeepEqual(got, want) {
			t.Errorf("ValueOf(%q) = %#v, %v; want %#v", key, got, err, want)
		}
		if err := conf.SetValue(key, got); err != nil {
			t.Errorf("SetValue(%q, %#v): %v", key, got, err)
		}
	}
}

// sectionType is the Section interface type.
var sectionType = reflect.TypeOf((*Section)(nil)).Elem()

// Every section, including embedded ones, implements Section, and its
// Flatten keys (which use the section's JSCK* constant) line up with its cfg
// tag in the parent. A section type used under more than one key anywhere in
// the config, such as JSCRateLimitRule, has no constant, so its keys are
// unprefixed. Each section's Map, TypeOf, ValueOf and SetValue agree with the
// whole configuration's view of the same keys, and so do those of each item
// in a list of sections. Sections are found by walking JobSearchConfig, so a
// new section is checked without being listed anywhere.
func TestSections(t *testing.T) {
	conf := defaultConfig(t)
	if !reflect.PointerTo(reflect.TypeOf(conf)).Implements(sectionType) {
		t.Error("*JobSearchConfig does not implement Section")
	}

	all := conf.Flatten()
	uses := map[reflect.Type]int{}
	countSections(uses, reflect.TypeOf(conf))
	checkSections(t, &conf, all, uses, "", reflect.ValueOf(&conf).Elem())
}

// countSections counts how many fields of each section type there are in the
// tree under section.
func countSections(uses map[reflect.Type]int, section reflect.Type) {
	for _, f := range fieldsOf(section) {
		if f.section {
			uses[f.fieldType]++
			countSections(uses, f.fieldType)
		}
	}
}

func checkSections(
	t *testing.T,
	conf *JobSearchConfig,
	all map[string]any,
	uses map[reflect.Type]int,
	prefix string,
	section reflect.Value,
) {
	t.Helper()
	for _, f := range fieldsOf(section.Type()) {
		key := joinKey(prefix, f.key)
		if isSectionList(f.fieldType) {
			checkSectionList(t, all, key, section.FieldByIndex(f.index))
		}
		if !f.section {
			continue
		}

		fv := section.FieldByIndex(f.index)
		name := fv.Type().Name()
		if !fv.Addr().Type().Implements(sectionType) {
			t.Errorf("*%s does not implement Section", name)
			continue
		}
		checkEmbedded(t, fv.Type())

		keys := fv.Addr().Interface().(Section).Flatten()
		keyPrefix := prefix
		if uses[f.fieldType] > 1 {
			keyPrefix = key
		}
		for k := range keys {
			if _, ok := all[joinKey(keyPrefix, k)]; !ok {
				t.Errorf(
					"%s.Flatten() key %q does not match its cfg tag %q", name, k, key,
				)
			}
		}

		// The section's own keys, relative to it, with the whole
		// configuration's values and kinds for them.
		want := map[string]any{}
		kinds := map[string]reflect.Kind{}
		for k, v := range all {
			if rel, ok := strings.CutPrefix(k, key+"."); ok {
				want[rel] = v
				kinds[rel], _ = conf.TypeOf(k)
			}
		}
		checkSectionMethods(t, name, fv, want, kinds)
		checkSections(t, conf, all, uses, key, fv)
	}
}

// checkSectionList checks the items of the list of sections at key implement
// Section and that their methods agree with the list's value in all.
func checkSectionList(
	t *testing.T, all map[string]any, key string, list reflect.Value,
) {
	t.Helper()
	name := list.Type().Elem().Name()
	if !reflect.PointerTo(list.Type().Elem()).Implements(sectionType) {
		t.Errorf("*%s (items of %s) does not implement Section", name, key)
		return
	}

	items, _ := all[key].([]map[string]any)
	if len(items) != list.Len() {
		t.Errorf("%s has %d items; Flatten gives %d", key, list.Len(), len(items))
		return
	}

	for i := range list.Len() {
		item, itemName := list.Index(i), fmt.Sprintf("%s[%d]", key, i)
		want := flattenMap("", items[i])

		// Items are not prefixed, and their kinds are their fields' kinds.
		got := item.Addr().Interface().(Section).Flatten()
		if !reflect.DeepEqual(got, want) {
			t.Errorf("%s.Flatten() =\n%v\nwant\n%v", itemName, got, want)
		}

		kinds := map[string]reflect.Kind{}
		for k := range want {
			_, f, _ := lookup(item, k)
			kinds[k] = kindOf(f.fieldType)
		}
		checkSectionMethods(t, itemName, item, want, kinds)
	}
}

// checkSectionMethods checks section's Map, TypeOf, ValueOf and SetValue
// against want, its keys and values, and kinds, their kinds.
// Setting each key to its own value must succeed and leave section unchanged.
func checkSectionMethods(
	t *testing.T,
	name string,
	section reflect.Value,
	want map[string]any,
	kinds map[string]reflect.Kind,
) {
	t.Helper()
	s := section.Addr().Interface().(Section)
	if got := flattenMap("", s.Map()); !reflect.DeepEqual(got, want) {
		t.Errorf("%s.Map() =\n%v\nwant\n%v", name, got, want)
	}

	before := section.Interface()
	for k, v := range want {
		if kind, err := s.TypeOf(k); err != nil || kind != kinds[k] {
			t.Errorf("%s.TypeOf(%q) = %v, %v; want %v", name, k, kind, err, kinds[k])
		}
		if got, err := s.ValueOf(k); err != nil || !reflect.DeepEqual(got, v) {
			t.Errorf("%s.ValueOf(%q) = %#v, %v; want %#v", name, k, got, err, v)
		}
		if err := s.SetValue(k, v); err != nil {
			t.Errorf("%s.SetValue(%q, %#v): %v", name, k, v, err)
		}
	}

	if !reflect.DeepEqual(section.Interface(), before) {
		t.Errorf("%s changed by setting its keys to their own values", name)
	}
}

// flattenMap flattens a map with nested maps, as Map gives, into dotted keys
// prefixed with prefix (if non-empty).
func flattenMap(prefix string, m map[string]any) map[string]any {
	flat := map[string]any{}
	for k, v := range m {
		if nested, ok := v.(map[string]any); ok {
			maps.Copy(flat, flattenMap(joinKey(prefix, k), nested))
		} else {
			flat[joinKey(prefix, k)] = v
		}
	}
	return flat
}

// checkEmbedded checks that structs embedded in a section, such as
// JSCSourcesSource, implement Section too.
func checkEmbedded(t *testing.T, section reflect.Type) {
	t.Helper()
	for i := 0; i < section.NumField(); i++ {
		sf := section.Field(i)
		if !sf.Anonymous || sf.Type.Kind() != reflect.Struct {
			continue
		}
		if !reflect.PointerTo(sf.Type).Implements(sectionType) {
			t.Errorf(
				"*%s (embedded in %s) does not implement Section",
				sf.Type.Name(),
				section.Name(),
			)
		}
		checkEmbedded(t, sf.Type)
	}
}