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package acme

import (
	"crypto/x509"
	"encoding/json"
	"errors"
	"log"
	"net/http"
	"regexp"
	"time"
)

// Provider ...
type Provider struct {
	Directory
	nonces chan string
	http.Client
	http.Transport
	poll time.Duration
}

var (
	errNoNonces    = errors.New("out of nonces")
	errContentType = errors.New("unknown content type")
	errChalType    = errors.New("unknown challenge")
	errStatus      = errors.New("unexpected status")
)

const (
	mimeJson    = "application/json"
	mimeJose    = "application/jose+json"
	mimeProblem = "application/problem+json"
	mimePkix    = "application/pkix-cert"
)

// RoundTrip implements RoundTipper
func (p Provider) RoundTrip(req *http.Request) (*http.Response, error) {
	resp, err := p.Transport.RoundTrip(req)
	if err != nil {
		return nil, err
	}
	if nonce := resp.Header.Get("Replay-Nonce"); nonce != "" {
		if len(p.nonces) == cap(p.nonces) {
			<-p.nonces // drop oldest
		}
		p.nonces <- nonce
	}
	// not sure if it belongs here
	if resp.Header.Get("Content-Type") == mimeProblem {
		defer resp.Body.Close()
		return nil, problem(resp.Body)
	}
	return resp, nil
}

// Nonce implements jose nonce provider
func (p Provider) Nonce() (string, error) {
	select {
	case nonce := <-p.nonces:
		return nonce, nil
	default:
		return "", errNoNonces
	}
}

// DialProvider fetches directory and initializes nonce
func DialProvider(directory string) (*Provider, error) {
	p := &Provider{
		nonces: make(chan string, 3),
		poll:   time.Second,
	}
	p.Client = http.Client{
		Transport: p,
		Timeout:   time.Duration(5 * time.Second),
	}
	resp, err := p.Get(directory)
	if err != nil {
		return nil, err
	}
	return p, parseJson(resp, &p.Directory)
}

func (p *Provider) post(uri string, s Signer, v interface{}) (*http.Response, error) {
	msg, err := json.Marshal(v)
	if err != nil {
		return nil, err
	}
	signed, err := s.Sign(msg, p)
	if err != nil {
		return nil, err
	}
	return p.Post(uri, mimeJose, signed)
}

type nextStep struct {
	Link     map[string]string
	Location string
}

var linksRe = regexp.MustCompile(`^<(.*)>;rel="(.*)"`)

func parseHeader(resp *http.Response) nextStep {
	var ns nextStep
	if lo, _ := resp.Location(); lo != nil {
		ns.Location = lo.String()
	}
	ns.Link = make(map[string]string)
	for _, li := range resp.Header["Link"] {
		re := linksRe.FindStringSubmatch(li)
		if len(re) == 3 {
			ns.Link[re[2]] = re[1]
		}
	}
	return ns
}

func parseJson(resp *http.Response, v interface{}) error {
	defer resp.Body.Close()
	if resp.Header.Get("Content-Type") != mimeJson {
		return errContentType
	}
	return json.NewDecoder(resp.Body).Decode(v)
}

func parseCert(resp *http.Response) (*x509.Certificate, error) {
	defer resp.Body.Close()
	if resp.Header.Get("Content-Type") != mimePkix {
		return nil, errContentType
	}
	return readCert(resp.Body)
}

func (p *Provider) Register(s Signer, c Contacts) error {
	// first step: new-reg
	req := &Registration{
		Resource: ResNewReg,
		Contact:  c,
	}
	resp, err := p.post(p.NewReg, s, req)
	if err != nil && err.(Problem).Err != ErrMalformed {
		return err
	}
	ns := parseHeader(resp)

	// second step: reg, agree to tos
	req = &Registration{
		Resource:  ResReg,
		Agreement: ns.Link["terms-of-service"],
	}
	resp, err = p.post(ns.Location, s, req)
	if err != nil {
		return err
	}
	resp.Body.Close()
	return nil
}

func (p *Provider) solve(s Signer, ch Challenge, sol Solver) error {
	ka, err := s.KeyAuth(ch.Token)
	if err != nil {
		return err
	}

	err = sol.Solve(ch.Token, ka)
	if err != nil {
		return err
	}
	defer sol.Solved()

	// update challenge
	ch.Resource = ResChallenge
	ch.KeyAuthorization = ka

	resp, err := p.post(ch.URI, s, ch)
	if err != nil {
		return err
	}
	ns := parseHeader(resp)

	if err := p.pollStatus(ns.Location); err != nil {
		return err
	}
	return nil
}

func (p *Provider) authz(s Signer, domain string, sol map[ChalType]Solver) error {
	// first step: pocke
	req := &Authorization{
		Resource: ResNewAuthz,
		Identifier: Identifier{
			Type:  IdentDNS,
			Value: domain,
		},
	}
	resp, err := p.post(p.NewAuthz, s, req)
	if err != nil {
		return err
	}
	err = parseJson(resp, req)
	if err != nil {
		return err
	}
	// second step: choose and start solver
	for _, ch := range req.Supported(sol) {
		if err = p.solve(s, ch, sol[ch.Type]); err != nil {
			return err
		}
	}
	return nil
}

func (p *Provider) Authz(s Signer, d *Desire) error {
	for _, domain := range d.altnames {
		if err := p.authz(s, domain, d.solver); err != nil {
			return err
		}
	}
	return nil
}

func (p *Provider) pollStatus(uri string) error {
	t := time.NewTicker(p.poll)
	defer t.Stop()
	for range t.C {
		resp, err := p.Get(uri)
		if err != nil {
			return err
		}
		req := new(Challenge)
		err = parseJson(resp, req)
		if err != nil {
			return err
		}
		if req.Err != nil {
			return req.Err
		}
		log.Println("status", req.Status)
		if req.Status == StatusValid {
			return nil
		}
	}
	return nil
}

func (p *Provider) Bundle(s Signer, d *Desire) error {
	// first step: post csr
	csr, err := d.CSR()
	if err != nil {
		return err
	}
	req := &CSR{
		Resource: ResNewCert,
		CSR:      csr,
	}
	resp, err := p.post(p.NewCert, s, req)
	if err != nil {
		return err
	}
	crt, err := parseCert(resp)
	if err != nil {
		return err
	}
	d.cert = append(d.cert, crt)
	ns := parseHeader(resp)

	// second step: cet CA
	resp, err = p.Get(ns.Link["up"])
	if err != nil {
		return err
	}
	crt, err = parseCert(resp)
	if err != nil {
		return err
	}
	d.cert = append(d.cert, crt)

	return nil
}