package pastee

import (
	"bytes"
	"encoding/json"
	"io"
	"math/rand"
	"net/http"
	"net/url"
	"strconv"
	"time"

	"paste.ee/go/cryptojs"
)

func New(key string) *Pastee {
	return &Pastee{ApiKey: key, Base: "https://api.paste.ee/v1", Client: &http.Client{Timeout: time.Minute}}
}

func (p *Pastee) Authenticate(username, password string) (*AuthResponse, error) {
	body, err := json.Marshal(&authRequest{username, password})

	if err != nil {
		return nil, err
	}

	req, err := p.newRequest("POST", "users/authenticate", bytes.NewReader(body))

	if err != nil {
		return nil, err
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Content-Length", strconv.Itoa(len(body)))

	res, err := p.Client.Do(req)

	if err != nil {
		return nil, err
	}

	defer res.Body.Close()

	var response AuthResponse

	if err := json.NewDecoder(res.Body).Decode(&response); err != nil {
		return nil, err
	}

	return &response, nil
}

func (p *Pastee) List() (*PasteListResponse, error) {
	q := &url.Values{}
	q.Set("perpage", "25")
	q.Set("page", "1")

	req, err := p.newRequest("GET", "pastes?" + q.Encode(), nil)

	if err != nil {
		return nil, err
	}

	res, err := p.Client.Do(req)

	if err != nil {
		return nil, err
	}

	defer res.Body.Close()

	var response PasteListResponse

	if err := json.NewDecoder(res.Body).Decode(&response); err != nil {
		return nil, err
	}

	return &response, nil
}

func (p *Pastee) Get(id string) (*Paste, error) {
	req, err := p.newRequest("GET", "pastes/" + id, nil)

	if err != nil {
		return nil, err
	}

	res, err := p.Client.Do(req)

	if err != nil {
		return nil, err
	}

	defer res.Body.Close()

	var response Paste

	if err := json.NewDecoder(res.Body).Decode(&response); err != nil {
		return nil, err
	}

	return &response, nil
}

func (p *Pastee) Submit(paste *Paste) (*PasteResponse, error) {
	var key string

	if paste.Encrypted {
		key = RandStringBytesMaskImprSrc(32)

		var err error

		for _, section := range paste.Sections {
			section.Contents, err = cryptojs.Encrypt(section.Contents, key)

			if err != nil {
				return nil, err
			}
		}
	}

	body, err := json.Marshal(paste)

	if err != nil {
		return nil, err
	}

	req, err := p.newRequest("POST", "pastes", bytes.NewReader(body))

	if err != nil {
		return nil, err
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Content-Length", strconv.Itoa(len(body)))

	res, err := p.Client.Do(req)

	if err != nil {
		return nil, err
	}

	defer res.Body.Close()

	var response PasteResponse

	if err := json.NewDecoder(res.Body).Decode(&response); err != nil {
		return nil, err
	}

	if key != "" {
		response.Key = key
	}

	return &response, nil
}

func (p *Pastee) newRequest(method, path string, body io.Reader) (*http.Request, error) {
	req, err := http.NewRequest(method, p.Base + "/" + path, body)

	if err != nil {
		return nil, err
	}

	req.Header.Set("X-Auth-Token", p.ApiKey)

	return req, nil
}

const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
const (
	letterIdxBits = 6                    // 6 bits to represent a letter index
	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
)

var src = rand.NewSource(time.Now().UnixNano())

func RandStringBytesMaskImprSrc(n int) string {
	b := make([]byte, n)
	// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
		if remain == 0 {
			cache, remain = src.Int63(), letterIdxMax
		}
		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
			b[i] = letterBytes[idx]
			i--
		}
		cache >>= letterIdxBits
		remain--
	}

	return string(b)
}