package contracts

import (
	"bytes"
	"embed"
	"fmt"
	"io/fs"
	"path"
	"strings"

	"github.com/santhosh-tekuri/jsonschema/v6"
)

// Files contains the shared contract at the project's pinned submodule commit.
// Runtime code never reads a checkout or resolves schema refs online.
//
//go:embed schema/*.json schema/examples
var Files embed.FS

// ReadCurrent reads only shared root schemas and MQ topology.
// There is no fallback to historical contracts or project-local copies.
func ReadCurrent(name string) ([]byte, error) {
	if name != path.Base(name) || strings.Contains(name, "\\") {
		return nil, fmt.Errorf("invalid current contract %q", name)
	}
	if name != "mq-topology.json" && !strings.HasSuffix(name, ".schema.json") {
		return nil, fmt.Errorf("invalid current contract %q", name)
	}
	return Files.ReadFile(path.Join("schema", name))
}

type offlineSchemaLoader struct{}

func (offlineSchemaLoader) Load(url string) (any, error) {
	return nil, fmt.Errorf("unregistered shared schema reference %q; network loading is disabled", url)
}

// CompileCurrent registers all canonical split schemas before compiling an
// entrypoint. Unregistered references fail explicitly, without network access.
func CompileCurrent(name string) (*jsonschema.Schema, error) {
	if _, err := ReadCurrent(name); err != nil {
		return nil, err
	}
	if !strings.HasSuffix(name, ".schema.json") {
		return nil, fmt.Errorf("not a schema: %q", name)
	}
	compiler := jsonschema.NewCompiler()
	compiler.AssertFormat()
	compiler.UseLoader(offlineSchemaLoader{})
	files, err := fs.Glob(Files, "schema/*.schema.json")
	if err != nil {
		return nil, err
	}
	var resource string
	for _, file := range files {
		data, err := Files.ReadFile(file)
		if err != nil {
			return nil, err
		}
		doc, err := jsonschema.UnmarshalJSON(bytes.NewReader(data))
		if err != nil {
			return nil, fmt.Errorf("decode shared schema %s: %w", file, err)
		}
		object, ok := doc.(map[string]any)
		if !ok {
			return nil, fmt.Errorf("shared schema %s must be an object", file)
		}
		id, ok := object["$id"].(string)
		if !ok || id == "" {
			return nil, fmt.Errorf("shared schema %s is missing $id", file)
		}
		if err := compiler.AddResource(id, doc); err != nil {
			return nil, fmt.Errorf("register shared schema %s: %w", file, err)
		}
		if path.Base(file) == name {
			resource = id
		}
	}
	schema, err := compiler.Compile(resource)
	if err != nil {
		return nil, fmt.Errorf("compile shared schema %s: %w", name, err)
	}
	return schema, nil
}