package openapi3

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
)

// T is the root of an OpenAPI v3 document
// See https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.3.md#openapi-object
type T struct {
	Extensions map[string]interface{} `json:"-" yaml:"-"`

	OpenAPI      string               `json:"openapi" yaml:"openapi"` // Required
	Components   *Components          `json:"components,omitempty" yaml:"components,omitempty"`
	Info         *Info                `json:"info" yaml:"info"`   // Required
	Paths        Paths                `json:"paths" yaml:"paths"` // Required
	Security     SecurityRequirements `json:"security,omitempty" yaml:"security,omitempty"`
	Servers      Servers              `json:"servers,omitempty" yaml:"servers,omitempty"`
	Tags         Tags                 `json:"tags,omitempty" yaml:"tags,omitempty"`
	ExternalDocs *ExternalDocs        `json:"externalDocs,omitempty" yaml:"externalDocs,omitempty"`

	visited visitedComponent
}

// MarshalJSON returns the JSON encoding of T.
func (doc T) MarshalJSON() ([]byte, error) {
	m := make(map[string]interface{}, 4+len(doc.Extensions))
	for k, v := range doc.Extensions {
		m[k] = v
	}
	m["openapi"] = doc.OpenAPI
	if x := doc.Components; x != nil {
		m["components"] = x
	}
	m["info"] = doc.Info
	m["paths"] = doc.Paths
	if x := doc.Security; len(x) != 0 {
		m["security"] = x
	}
	if x := doc.Servers; len(x) != 0 {
		m["servers"] = x
	}
	if x := doc.Tags; len(x) != 0 {
		m["tags"] = x
	}
	if x := doc.ExternalDocs; x != nil {
		m["externalDocs"] = x
	}
	return json.Marshal(m)
}

// UnmarshalJSON sets T to a copy of data.
func (doc *T) UnmarshalJSON(data []byte) error {
	type TBis T
	var x TBis
	if err := json.Unmarshal(data, &x); err != nil {
		return err
	}
	_ = json.Unmarshal(data, &x.Extensions)
	delete(x.Extensions, "openapi")
	delete(x.Extensions, "components")
	delete(x.Extensions, "info")
	delete(x.Extensions, "paths")
	delete(x.Extensions, "security")
	delete(x.Extensions, "servers")
	delete(x.Extensions, "tags")
	delete(x.Extensions, "externalDocs")
	*doc = T(x)
	return nil
}

func (doc *T) AddOperation(path string, method string, operation *Operation) {
	if doc.Paths == nil {
		doc.Paths = make(Paths)
	}
	pathItem := doc.Paths[path]
	if pathItem == nil {
		pathItem = &PathItem{}
		doc.Paths[path] = pathItem
	}
	pathItem.SetOperation(method, operation)
}

func (doc *T) AddServer(server *Server) {
	doc.Servers = append(doc.Servers, server)
}

// Validate returns an error if T does not comply with the OpenAPI spec.
// Validations Options can be provided to modify the validation behavior.
func (doc *T) Validate(ctx context.Context, opts ...ValidationOption) error {
	ctx = WithValidationOptions(ctx, opts...)

	if doc.OpenAPI == "" {
		return errors.New("value of openapi must be a non-empty string")
	}

	var wrap func(error) error
	// NOTE: only mention info/components/paths/... key in this func's errors.

	wrap = func(e error) error { return fmt.Errorf("invalid components: %w", e) }
	if v := doc.Components; v != nil {
		if err := v.Validate(ctx); err != nil {
			return wrap(err)
		}
	}

	wrap = func(e error) error { return fmt.Errorf("invalid info: %w", e) }
	if v := doc.Info; v != nil {
		if err := v.Validate(ctx); err != nil {
			return wrap(err)
		}
	} else {
		return wrap(errors.New("must be an object"))
	}

	wrap = func(e error) error { return fmt.Errorf("invalid paths: %w", e) }
	if v := doc.Paths; v != nil {
		if err := v.Validate(ctx); err != nil {
			return wrap(err)
		}
	} else {
		return wrap(errors.New("must be an object"))
	}

	wrap = func(e error) error { return fmt.Errorf("invalid security: %w", e) }
	if v := doc.Security; v != nil {
		if err := v.Validate(ctx); err != nil {
			return wrap(err)
		}
	}

	wrap = func(e error) error { return fmt.Errorf("invalid servers: %w", e) }
	if v := doc.Servers; v != nil {
		if err := v.Validate(ctx); err != nil {
			return wrap(err)
		}
	}

	wrap = func(e error) error { return fmt.Errorf("invalid tags: %w", e) }
	if v := doc.Tags; v != nil {
		if err := v.Validate(ctx); err != nil {
			return wrap(err)
		}
	}

	wrap = func(e error) error { return fmt.Errorf("invalid external docs: %w", e) }
	if v := doc.ExternalDocs; v != nil {
		if err := v.Validate(ctx); err != nil {
			return wrap(err)
		}
	}

	return validateExtensions(ctx, doc.Extensions)
}