package opentsdb

import (
    "fmt"
    "encoding/json"
	"io"
	"io/ioutil"
	"net/http"
	"net/http/httputil"
	"net/url"
	"bytes"
	"compress/gzip"
	"log"
)

type HttpMetric struct {
	Metric    string `json:"metric"`
	Timestamp int64 `json:"timestamp"`
	Value     string `json:"value"`
	Tags      map[string]string `json:"tags"`
}


type openTSDBHttp struct {
	Host string
	Port int
    BatchSize int
	Debug bool

    metricCounter int
    body requestBody
}

type requestBody struct {
    b bytes.Buffer
    g *gzip.Writer

    dbgB bytes.Buffer

    w io.Writer
    enc *json.Encoder

    empty bool
}

func (r *requestBody) reset(debug bool) {
    r.b.Reset()
    r.dbgB.Reset()

    if r.g == nil {
        r.g = gzip.NewWriter(&r.b)
    } else {
        r.g.Reset(&r.b)
    }

    if debug {
        r.w = io.MultiWriter(r.g, &r.dbgB)
    } else {
        r.w = r.g
    }

    r.enc = json.NewEncoder(r.w)

    io.WriteString(r.w, "[")

    r.empty = true
}

func (r *requestBody) addMetric(metric *HttpMetric) error {
    if !r.empty {
        io.WriteString(r.w, ",")
    }

    if err := r.enc.Encode(metric); err != nil {
        return fmt.Errorf("Metric serialization error %s", err.Error())
    }

    r.empty = false

    return nil
}

func (r *requestBody) close() error {
    io.WriteString(r.w, "]")

    if err := r.g.Close(); err != nil {
        return fmt.Errorf("Error when closing gzip writer: %s", err.Error())
    }

    return nil
}

func (o *openTSDBHttp) sendDataPoint(metric *HttpMetric) error {
    if o.metricCounter == 0 {
        o.body.reset(o.Debug)
    }

    if err := o.body.addMetric(metric); err != nil {
        return err
    }

    o.metricCounter++
    if o.metricCounter == o.BatchSize {
        if err := o.flush(); err != nil {
            return err
        }

        o.metricCounter = 0
    }

    return nil
}

func (o *openTSDBHttp) flush() error {
    if o.metricCounter == 0 {
        return nil
    }

    o.body.close()

    u := url.URL {
		Scheme: "http",
		Host:   fmt.Sprintf("%s:%d", o.Host, o.Port),
		Path:   "/api/put",
	}

	if (o.Debug) {
		u.RawQuery = "details"
	}

	req, err := http.NewRequest("POST", u.String(), &o.body.b)
	if err != nil {
		return fmt.Errorf("Error when building request: %s", err.Error())
	}
	req.Header.Set("Content-Type", "applicaton/json")
	req.Header.Set("Content-Encoding", "gzip")

	if (o.Debug) {
		dump, err := httputil.DumpRequestOut(req, false)
		if err != nil {
			return fmt.Errorf("Error when dumping request: %s", err.Error())
		}

		fmt.Printf("Sending metrics:\n%s", dump)
		fmt.Printf("Body:\n%s\n\n", o.body.dbgB.String())
	}

    resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return fmt.Errorf("Error when sending metrics: %s", err.Error())
	}
	defer resp.Body.Close()

    if o.Debug {
		dump, err := httputil.DumpResponse(resp, true)
		if err != nil {
			return fmt.Errorf("Error when dumping response: %s", err.Error())
	    }

		fmt.Printf("Received response\n%s\n\n", dump)
	} else {
        // Important so http client reuse connection for next request if need be.
        io.Copy(ioutil.Discard, resp.Body)
    }

	if resp.StatusCode/100 != 2 {
		if resp.StatusCode/100 == 4 {
			log.Printf("WARNING: Received %d status code. Dropping metrics to avoid overflowing buffer.", resp.StatusCode)
		} else {
			return fmt.Errorf("Error when sending metrics.Received status %d", resp.StatusCode)
		}
	}

	return nil
}