package rpc

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/blang/semver/v4"
	"github.com/ipfs/boxo/ipld/merkledag"
	"github.com/ipfs/go-cid"
	legacy "github.com/ipfs/go-ipld-legacy"
	ipfs "github.com/ipfs/kubo"
	iface "github.com/ipfs/kubo/core/coreiface"
	caopts "github.com/ipfs/kubo/core/coreiface/options"
	dagpb "github.com/ipld/go-codec-dagpb"
	_ "github.com/ipld/go-ipld-prime/codec/dagcbor"
	"github.com/ipld/go-ipld-prime/node/basicnode"
	"github.com/mitchellh/go-homedir"
	ma "github.com/multiformats/go-multiaddr"
	manet "github.com/multiformats/go-multiaddr/net"
)

const (
	DefaultPathName = ".ipfs"
	DefaultPathRoot = "~/" + DefaultPathName
	DefaultApiFile  = "api"
	EnvDir          = "IPFS_PATH"
)

// ErrApiNotFound if we fail to find a running daemon.
var ErrApiNotFound = errors.New("ipfs api address could not be found")

// HttpApi implements github.com/ipfs/interface-go-ipfs-core/CoreAPI using
// IPFS HTTP API.
//
// For interface docs see
// https://godoc.org/github.com/ipfs/interface-go-ipfs-core#CoreAPI
type HttpApi struct {
	url         string
	httpcli     http.Client
	Headers     http.Header
	applyGlobal func(*requestBuilder)
	ipldDecoder *legacy.Decoder
	versionMu   sync.Mutex
	version     *semver.Version
}

// NewLocalApi tries to construct new HttpApi instance communicating with local
// IPFS daemon
//
// Daemon api address is pulled from the $IPFS_PATH/api file.
// If $IPFS_PATH env var is not present, it defaults to ~/.ipfs.
func NewLocalApi() (*HttpApi, error) {
	baseDir := os.Getenv(EnvDir)
	if baseDir == "" {
		baseDir = DefaultPathRoot
	}

	return NewPathApi(baseDir)
}

// NewPathApi constructs new HttpApi by pulling api address from specified
// ipfspath. Api file should be located at $ipfspath/api.
func NewPathApi(ipfspath string) (*HttpApi, error) {
	a, err := ApiAddr(ipfspath)
	if err != nil {
		if os.IsNotExist(err) {
			err = ErrApiNotFound
		}
		return nil, err
	}
	return NewApi(a)
}

// ApiAddr reads api file in specified ipfs path.
func ApiAddr(ipfspath string) (ma.Multiaddr, error) {
	baseDir, err := homedir.Expand(ipfspath)
	if err != nil {
		return nil, err
	}

	apiFile := filepath.Join(baseDir, DefaultApiFile)

	api, err := os.ReadFile(apiFile)
	if err != nil {
		return nil, err
	}

	return ma.NewMultiaddr(strings.TrimSpace(string(api)))
}

// NewApi constructs HttpApi with specified endpoint.
func NewApi(a ma.Multiaddr) (*HttpApi, error) {
	transport := &http.Transport{
		Proxy:             http.ProxyFromEnvironment,
		DisableKeepAlives: true,
	}

	network, address, err := manet.DialArgs(a)
	if err != nil {
		return nil, err
	}
	if network == "unix" {
		transport.DialContext = func(_ context.Context, _, _ string) (net.Conn, error) {
			return net.Dial("unix", address)
		}
		c := &http.Client{
			Transport: transport,
		}
		// This will create an API client which
		// makes requests to `http://unix`.
		return NewURLApiWithClient(network, c)
	}

	c := &http.Client{
		Transport: transport,
	}

	return NewApiWithClient(a, c)
}

// NewApiWithClient constructs HttpApi with specified endpoint and custom http client.
func NewApiWithClient(a ma.Multiaddr, c *http.Client) (*HttpApi, error) {
	_, url, err := manet.DialArgs(a)
	if err != nil {
		return nil, err
	}

	if a, err := ma.NewMultiaddr(url); err == nil {
		_, host, err := manet.DialArgs(a)
		if err == nil {
			url = host
		}
	}

	proto := "http://"

	// By default, DialArgs is going to provide details suitable for connecting
	// a socket to, but not really suitable for making an informed choice of http
	// protocol.  For multiaddresses specifying tls and/or https we want to make
	// a https request instead of a http request.
	protocols := a.Protocols()
	for _, p := range protocols {
		if p.Code == ma.P_HTTPS || p.Code == ma.P_TLS {
			proto = "https://"
			break
		}
	}

	return NewURLApiWithClient(proto+url, c)
}

func NewURLApiWithClient(url string, c *http.Client) (*HttpApi, error) {
	decoder := legacy.NewDecoder()
	// Add support for these codecs to match what is done in the merkledag library
	// Note: to match prior behavior the go-ipld-prime CBOR decoder is manually included
	// TODO: allow the codec registry used to be configured by the caller not through a global variable
	decoder.RegisterCodec(cid.DagProtobuf, dagpb.Type.PBNode, merkledag.ProtoNodeConverter)
	decoder.RegisterCodec(cid.Raw, basicnode.Prototype.Bytes, merkledag.RawNodeConverter)

	api := &HttpApi{
		url:         url,
		httpcli:     *c,
		Headers:     make(map[string][]string),
		applyGlobal: func(*requestBuilder) {},
		ipldDecoder: decoder,
	}

	// We don't support redirects.
	api.httpcli.CheckRedirect = func(_ *http.Request, _ []*http.Request) error {
		return fmt.Errorf("unexpected redirect")
	}

	return api, nil
}

func (api *HttpApi) WithOptions(opts ...caopts.ApiOption) (iface.CoreAPI, error) {
	options, err := caopts.ApiOptions(opts...)
	if err != nil {
		return nil, err
	}

	subApi := &HttpApi{
		url:     api.url,
		httpcli: api.httpcli,
		Headers: api.Headers,
		applyGlobal: func(req *requestBuilder) {
			if options.Offline {
				req.Option("offline", options.Offline)
			}
		},
		ipldDecoder: api.ipldDecoder,
	}

	return subApi, nil
}

func (api *HttpApi) Request(command string, args ...string) RequestBuilder {
	headers := make(map[string]string)
	if api.Headers != nil {
		for k := range api.Headers {
			headers[k] = api.Headers.Get(k)
		}
	}
	return &requestBuilder{
		command: command,
		args:    args,
		shell:   api,
		headers: headers,
	}
}

func (api *HttpApi) Unixfs() iface.UnixfsAPI {
	return (*UnixfsAPI)(api)
}

func (api *HttpApi) Block() iface.BlockAPI {
	return (*BlockAPI)(api)
}

func (api *HttpApi) Dag() iface.APIDagService {
	return (*HttpDagServ)(api)
}

func (api *HttpApi) Name() iface.NameAPI {
	return (*NameAPI)(api)
}

func (api *HttpApi) Key() iface.KeyAPI {
	return (*KeyAPI)(api)
}

func (api *HttpApi) Pin() iface.PinAPI {
	return (*PinAPI)(api)
}

func (api *HttpApi) Object() iface.ObjectAPI {
	return (*ObjectAPI)(api)
}

func (api *HttpApi) Swarm() iface.SwarmAPI {
	return (*SwarmAPI)(api)
}

func (api *HttpApi) PubSub() iface.PubSubAPI {
	return (*PubsubAPI)(api)
}

func (api *HttpApi) Routing() iface.RoutingAPI {
	return (*RoutingAPI)(api)
}

func (api *HttpApi) loadRemoteVersion() (*semver.Version, error) {
	api.versionMu.Lock()
	defer api.versionMu.Unlock()

	if api.version == nil {
		ctx, cancel := context.WithDeadline(context.Background(), time.Now().Add(time.Second*30))
		defer cancel()

		resp, err := api.Request("version").Send(ctx)
		if err != nil {
			return nil, err
		}
		if resp.Error != nil {
			return nil, resp.Error
		}
		defer resp.Close()
		var out ipfs.VersionInfo
		dec := json.NewDecoder(resp.Output)
		if err := dec.Decode(&out); err != nil {
			return nil, err
		}

		remoteVersion, err := semver.New(out.Version)
		if err != nil {
			return nil, err
		}

		api.version = remoteVersion
	}

	return api.version, nil
}
