// Copyright Istio Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package codegen

import (
	"bytes"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"sort"
	"strings"
	"text/template"

	"istio.io/istio/pilot/pkg/features"
	"istio.io/istio/pkg/config/schema/ast"
	"istio.io/istio/pkg/test/env"
	"istio.io/istio/pkg/util/strcase"
)

func Run() error {
	inp, err := buildInputs()
	if err != nil {
		return err
	}

	// Include synthetic types used for XDS pushes
	kindEntries := append([]colEntry{
		{
			Resource: &ast.Resource{Identifier: "Address", Kind: "Address", Version: "internal", Group: "internal"},
		},
		{
			Resource: &ast.Resource{Identifier: "DNSName", Kind: "DNSName", Version: "internal", Group: "internal"},
		},
		{
			Resource: &ast.Resource{Identifier: "TypeUrl", Kind: "TypeUrl", Version: "internal", Group: "internal"},
		},
	}, inp.Entries...)

	sort.Slice(kindEntries, func(i, j int) bool {
		return strings.Compare(kindEntries[i].Resource.Identifier, kindEntries[j].Resource.Identifier) < 0
	})

	// filter to only types agent needs (to keep binary small)
	agentEntries := []colEntry{}
	for _, e := range inp.Entries {
		if strings.Contains(e.Resource.ProtoPackage, "istio.io") &&
			e.Resource.Kind != "EnvoyFilter" {
			agentEntries = append(agentEntries, e)
		}
	}

	// add MCS types
	gvrEntries := append([]colEntry{
		{Resource: &ast.Resource{Identifier: "ServiceExport", Plural: "serviceexports", Version: features.MCSAPIVersion, Group: features.MCSAPIGroup}},
		{Resource: &ast.Resource{Identifier: "ServiceImport", Plural: "serviceimports", Version: features.MCSAPIVersion, Group: features.MCSAPIGroup}},
	}, inp.Entries...)

	// Build a deduplicated list of Kind names for KebabKind function
	seenKinds := make(map[string]bool)
	var uniqueKinds []string
	for _, e := range inp.Entries {
		if !seenKinds[e.Resource.Kind] {
			seenKinds[e.Resource.Kind] = true
			uniqueKinds = append(uniqueKinds, e.Resource.Kind)
		}
	}
	sort.Strings(uniqueKinds)

	return errors.Join(
		writeTemplate("pkg/config/schema/gvk/resources.gen.go", gvkTemplate, map[string]any{
			"Entries":     inp.Entries,
			"UniqueKinds": uniqueKinds,
			"PackageName": "gvk",
		}),
		writeTemplate("pkg/config/schema/gvr/resources.gen.go", gvrTemplate, map[string]any{
			"Entries":     gvrEntries,
			"PackageName": "gvr",
		}),
		writeTemplate("pilot/pkg/config/kube/crdclient/types.gen.go", crdclientTemplate, map[string]any{
			"Entries":     inp.Entries,
			"Packages":    inp.Packages,
			"PackageName": "crdclient",
		}),
		writeTemplate("pkg/config/schema/kubetypes/resources.gen.go", typesTemplate, map[string]any{
			"Entries":     inp.Entries,
			"Packages":    inp.Packages,
			"PackageName": "kubetypes",
		}),
		writeTemplate("pkg/config/schema/kubeclient/resources.gen.go", clientsTemplate, map[string]any{
			"Entries":     inp.Entries,
			"Packages":    inp.Packages,
			"PackageName": "kubeclient",
		}),
		writeTemplate("pkg/config/schema/kind/resources.gen.go", kindTemplate, map[string]any{
			"Entries":     kindEntries,
			"PackageName": "kind",
		}),
		writeTemplate("pkg/config/schema/collections/collections.gen.go", collectionsTemplate, map[string]any{
			"Entries":      inp.Entries,
			"Packages":     inp.Packages,
			"PackageName":  "collections",
			"FilePrefix":   "//go:build !agent",
			"CustomImport": `  "istio.io/istio/pkg/config/validation/envoyfilter"`,
		}),
		writeTemplate("pkg/config/schema/collections/collections.agent.gen.go", collectionsTemplate, map[string]any{
			"Entries":      agentEntries,
			"Packages":     inp.Packages,
			"PackageName":  "collections",
			"FilePrefix":   "//go:build agent",
			"CustomImport": "",
		}),
	)
}

func writeTemplate(path, tmpl string, i any) error {
	t, err := applyTemplate(tmpl, i)
	if err != nil {
		return fmt.Errorf("apply template %v: %v", path, err)
	}
	dst := filepath.Join(env.IstioSrc, path)
	if err = os.WriteFile(dst, []byte(t), os.ModePerm); err != nil {
		return fmt.Errorf("write template %v: %v", path, err)
	}
	c := exec.Command("goimports", "-w", "-local", "istio.io", dst)
	c.Stdout = os.Stdout
	c.Stderr = os.Stderr
	return c.Run()
}

// camelCaseToKebabCase wraps strcase.CamelCaseToKebabCase for use in templates.
func camelCaseToKebabCase(s string) string {
	return strcase.CamelCaseToKebabCase(s)
}

func applyTemplate(tmpl string, i any) (string, error) {
	t := template.New("tmpl").Funcs(template.FuncMap{
		"contains":  strings.Contains,
		"kebabcase": camelCaseToKebabCase,
	})

	t2 := template.Must(t.Parse(tmpl))

	var b bytes.Buffer
	if err := t2.Execute(&b, i); err != nil {
		return "", err
	}

	return b.String(), nil
}
