package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"reflect"
	"sort"
	"strings"

	"github.com/iancoleman/strcase"
	"github.com/invopop/jsonschema"

	"github.com/anchore/syft/internal"
	"github.com/anchore/syft/internal/packagemetadata"
	syftJsonModel "github.com/anchore/syft/syft/format/syftjson/model"
)

/*
This method of creating the JSON schema only captures strongly typed fields for the purpose of integrations between syft
JSON output and integrations. The downside to this approach is that any values and types used on weakly typed fields
are not captured (empty interfaces). This means that pkg.Package.Metadata is not validated at this time. This approach
can be extended to include specific package metadata struct shapes in the future.
*/

var repoRoot string

func init() {
	var err error
	repoRoot, err = packagemetadata.RepoRoot()
	if err != nil {
		fmt.Println("unable to determine repo root")
		os.Exit(1)
	}
}

func main() {
	write(encode(build()))
}

func schemaID() jsonschema.ID {
	// Today we do not host the schemas at this address, but per the JSON schema spec we should be referencing
	// the schema by a URL in a domain we control. This is a placeholder for now.
	return jsonschema.ID(fmt.Sprintf("anchore.io/schema/syft/json/%s", internal.JSONSchemaVersion))
}

func assembleTypeContainer(items []any) (any, map[string]string) {
	structFields := make([]reflect.StructField, len(items))
	mapping := make(map[string]string, len(items))
	typesMissingNames := make([]reflect.Type, 0)
	for i, item := range items {
		itemType := reflect.TypeOf(item)

		jsonName := packagemetadata.JSONName(item)
		fieldName := strcase.ToCamel(jsonName)

		if jsonName == "" {
			typesMissingNames = append(typesMissingNames, itemType)
			continue
		}

		mapping[itemType.Name()] = fieldName

		structFields[i] = reflect.StructField{
			Name: fieldName,
			Type: itemType,
		}
	}

	if len(typesMissingNames) > 0 {
		fmt.Println("the following types are missing JSON names (manually curated in ./internal/packagemetadata/names.go):")
		for _, t := range typesMissingNames {
			fmt.Println("  - ", t.Name())
		}
		os.Exit(1)
	}

	structType := reflect.StructOf(structFields)
	return reflect.New(structType).Elem().Interface(), mapping
}

func build() *jsonschema.Schema {
	reflector := &jsonschema.Reflector{
		BaseSchemaID:              schemaID(),
		AllowAdditionalProperties: true,
		Namer: func(r reflect.Type) string {
			return strings.TrimPrefix(r.Name(), "JSON")
		},
		CommentMap: make(map[string]string),
	}

	// extract comments from Go source files to enrich schema descriptions
	//
	// note: AddGoComments parses from the module root and creates keys like "syft/pkg.TypeName",
	// but the reflector expects fully qualified paths like "github.com/anchore/syft/syft/pkg.TypeName".
	// We fix up the keys after extraction to match the expected format.
	if err := reflector.AddGoComments("github.com/anchore/syft", repoRoot); err != nil {
		fmt.Fprintf(os.Stderr, "warning: failed to extract Go comments: %v\n", err)
	} else {
		// fix up comment map keys to use fully qualified import paths
		// note: AddGoComments includes the absolute repo path WITHOUT the leading slash
		repoRootNoSlash := strings.TrimPrefix(repoRoot, "/")
		fixedMap := make(map[string]string)
		for k, v := range reflector.CommentMap {
			newKey := k
			if !strings.HasPrefix(k, "github.com/") {
				// key doesn't have module prefix, add it
				newKey = "github.com/anchore/syft/" + k
			} else if strings.Contains(k, repoRootNoSlash) {
				// key has the absolute repo path embedded, strip it
				// format: github.com/anchore/syft/Users/wagoodman/code/syft-manual/syft/pkg.Type
				// should be: github.com/anchore/syft/syft/pkg.Type
				newKey = strings.Replace(k, repoRootNoSlash+"/", "", 1)
			}
			fixedMap[newKey] = v
		}
		reflector.CommentMap = fixedMap

		// copy field comments for type aliases (e.g., type RpmArchive RpmDBEntry)
		copyAliasFieldComments(reflector.CommentMap, repoRoot)
	}

	pkgMetadataContainer, pkgMetadataMapping := assembleTypeContainer(packagemetadata.AllTypes())
	pkgMetadataContainerType := reflect.TypeOf(pkgMetadataContainer)

	// srcMetadataContainer := assembleTypeContainer(sourcemetadata.AllTypes())
	// srcMetadataContainerType := reflect.TypeOf(srcMetadataContainer)

	documentSchema := reflector.ReflectFromType(reflect.TypeOf(&syftJsonModel.Document{}))
	pkgMetadataSchema := reflector.ReflectFromType(reflect.TypeOf(pkgMetadataContainer))
	// srcMetadataSchema := reflector.ReflectFromType(reflect.TypeOf(srcMetadataContainer))

	// TODO: add source metadata types

	// inject the definitions of all packages metadata into the schema definitions

	var metadataNames []string
	for typeName, definition := range pkgMetadataSchema.Definitions {
		if typeName == pkgMetadataContainerType.Name() {
			// ignore the definition for the fake container
			continue
		}

		displayName, ok := pkgMetadataMapping[typeName]
		if ok {
			// this is a package metadata type...
			documentSchema.Definitions[displayName] = definition
			metadataNames = append(metadataNames, displayName)
		} else {
			// this is a type that the metadata type uses (e.g. DpkgFileRecord)
			documentSchema.Definitions[typeName] = definition
		}
	}

	// ensure the generated list of names is stable between runs
	sort.Strings(metadataNames)

	metadataTypes := []map[string]string{
		// allow for no metadata to be provided
		{"type": "null"},
	}
	for _, name := range metadataNames {
		metadataTypes = append(metadataTypes, map[string]string{
			"$ref": fmt.Sprintf("#/$defs/%s", name),
		})
	}

	// set the "anyOf" field for Package.Metadata to be a conjunction of several types
	documentSchema.Definitions["Package"].Properties.Set("metadata", map[string][]map[string]string{
		"anyOf": metadataTypes,
	})

	// warn about missing descriptions
	warnMissingDescriptions(documentSchema, metadataNames)

	return documentSchema
}

func encode(schema *jsonschema.Schema) []byte {
	newSchemaBuffer := new(bytes.Buffer)
	enc := json.NewEncoder(newSchemaBuffer)
	// prevent > and < from being escaped in the payload
	enc.SetEscapeHTML(false)
	enc.SetIndent("", "  ")
	err := enc.Encode(&schema)
	if err != nil {
		panic(err)
	}

	return newSchemaBuffer.Bytes()
}

func write(schema []byte) {
	schemaPath := filepath.Join(repoRoot, "schema", "json", fmt.Sprintf("schema-%s.json", internal.JSONSchemaVersion))
	latestSchemaPath := filepath.Join(repoRoot, "schema", "json", "schema-latest.json")

	if _, err := os.Stat(schemaPath); !os.IsNotExist(err) {
		// check if the schema is the same...
		existingFh, err := os.Open(schemaPath)
		if err != nil {
			panic(err)
		}

		existingSchemaBytes, err := io.ReadAll(existingFh)
		if err != nil {
			panic(err)
		}

		if bytes.Equal(existingSchemaBytes, schema) {
			// the generated schema is the same, bail with no error :)
			fmt.Println("No change to the existing schema!")
			os.Exit(0)
		}

		// the generated schema is different, bail with error :(
		fmt.Printf("Cowardly refusing to overwrite existing schema (%s)!\nSee the schema/json/README.md for how to increment\n", schemaPath)
		os.Exit(1)
	}

	fh, err := os.Create(schemaPath)
	if err != nil {
		panic(err)
	}
	defer fh.Close()

	_, err = fh.Write(schema)
	if err != nil {
		panic(err)
	}

	latestFile, err := os.Create(latestSchemaPath)
	if err != nil {
		panic(err)
	}
	defer latestFile.Close()

	_, err = latestFile.Write(schema)
	if err != nil {
		panic(err)
	}

	fmt.Printf("Wrote new schema to %q\n", schemaPath)
}