// Package influx provides functionality.
package influx

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"os"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/davecgh/go-spew/spew"
)

const (
	defaultAddr = "http://localhost:8428"
	// VictoriaMetrics uses MetricsQL, not Flux
	// Data model: metric names are {measurement}_{field}
)

var (
	initOnce sync.Once
	client   *http.Client
	// addr defaults to defaultAddr at declaration so callers (and
	// tests) can override it before the first lazy init runs.
	addr = defaultAddr
)

// ensureInit performs one-time setup of the HTTP client and TSDB
// address. It is called from every public function so that binaries
// which only import this package transitively (e.g. the distributed
// worker, which never reads or writes TSDB points) do not pay the
// init cost or emit a misleading "TSDB client initialized" log line.
// INFLUX_URL is read here so the address tracks the env var across
// process restarts without requiring explicit init from the caller.
//
// The env var is honored only when `addr` still equals the default.
// This lets tests (and any explicit caller) pre-set `addr` to a
// mock URL before the first public call fires; without this guard,
// CI runs where INFLUX_URL is exported in .env.ci.example would
// overwrite a test's mock server URL the moment initOnce fires,
// causing every QueryVM/* test to silently target a real TSDB.
func ensureInit() {
	initOnce.Do(func() {
		client = &http.Client{Timeout: 30 * time.Second}
		if addr == defaultAddr {
			if addrEnv := os.Getenv("INFLUX_URL"); addrEnv != "" {
				addr = addrEnv
			}
		}
		log.Println("TSDB client initialized for:", addr)
	})
}

// VMExportResponse represents VictoriaMetrics export response
type VMExportResponse struct {
	Metric     map[string]string `json:"metric"`
	Values     []json.Number     `json:"values"`
	Timestamps []int64           `json:"timestamps"`
}

// QueryVM performs a MetricsQL query against VictoriaMetrics
// QueryVM performs an export query against VictoriaMetrics.
// selector is a time series selector like `chttp_took{check="1146"}`.
// start is the RFC3339 or Unix timestamp for the beginning of the time range (can be empty).
func QueryVM(selector, start string) ([]VMExportResponse, error) {
	return QueryVMMany([]string{selector}, start)
}

// QueryVMMany exports several selectors in one request.
func QueryVMMany(selectors []string, start string) ([]VMExportResponse, error) {
	ensureInit()
	u, err := url.Parse(addr + "/api/v1/export")
	if err != nil {
		return nil, err
	}

	req, err := http.NewRequest("GET", u.String(), http.NoBody)
	if err != nil {
		return nil, err
	}

	q := req.URL.Query()
	for _, selector := range selectors {
		q.Add("match[]", selector)
	}
	if start != "" {
		q.Add("start", start)
	}
	req.URL.RawQuery = q.Encode()

	resp, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close() //nolint:errcheck

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("query failed with status %d: %s", resp.StatusCode, string(body))
	}

	var results []VMExportResponse
	decoder := json.NewDecoder(resp.Body)
	for {
		var result VMExportResponse
		if err := decoder.Decode(&result); err != nil {
			if err == io.EOF {
				break
			}
			return nil, err
		}
		results = append(results, result)
	}

	return results, nil
}

// MetricCheck identifies the duration series for a check.
type MetricCheck struct {
	Metric  string
	CheckID int64
}

// GetLastMany fetches a page's checks in one bounded VictoriaMetrics export.
func GetLastMany(checks []MetricCheck, hours int) (map[int64][]InfluxData, error) {
	out := make(map[int64][]InfluxData, len(checks))
	if len(checks) == 0 {
		return out, nil
	}
	if len(checks) > 500 {
		checks = checks[:500]
	}
	selectors := make([]string, 0, len(checks))
	for _, check := range checks {
		selectors = append(selectors, fmt.Sprintf(`%s_took{check="%d"}`, check.Metric, check.CheckID))
	}
	results, err := QueryVMMany(selectors, fmt.Sprintf("%d", time.Now().Add(-time.Duration(hours)*time.Hour).Unix()))
	if err != nil {
		return nil, err
	}
	for _, result := range results {
		checkID, err := strconv.ParseInt(result.Metric["check"], 10, 64)
		if err != nil {
			continue
		}
		state := result.Metric["state"]
		if state == "" {
			state = "UNK"
		}
		for i, ts := range result.Timestamps {
			var duration int64
			if i < len(result.Values) {
				duration, _ = result.Values[i].Int64()
			}
			out[checkID] = append(out[checkID], InfluxData{Time: time.Unix(ts/1000, (ts%1000)*1e6), Duration: duration, State: state})
		}
	}
	return out, nil
}

// InfluxData provides functionality. //nolint:revive // stutter intentional for clarity
type InfluxData struct {
	Time     time.Time `json:"time"`
	Duration int64     `json:"duration"`
	State    string    `json:"state"`
	Error    string    `json:"error,omitempty"`
	Warnings string    `json:"warnings,omitempty"`
}

// GetLast provides functionality.
func GetLast(metric string, check int64, hours int) ([]InfluxData, error) {
	ensureInit()
	// VictoriaMetrics export API: match[] selector + start time
	selector := fmt.Sprintf(`%s_took{check="%d"}`, metric, check)
	start := fmt.Sprintf("%d", time.Now().Add(-time.Duration(hours)*time.Hour).Unix())

	log.Println("TSDB query:", selector, "start:", start)
	results, err := QueryVM(selector, start)
	if err != nil {
		spew.Dump(err)
		log.Println("TSDB query error", err)
		return nil, err
	}

	log.Printf("Got %d result series from TSDB", len(results))

	influxData := make([]InfluxData, 0)

	// Process each time series (VictoriaMetrics returns one series per unique tag combination)
	for _, result := range results {
		state := result.Metric["state"]
		errorMsg := result.Metric["error"]
		warnings := result.Metric["warnings"]

		for i, ts := range result.Timestamps {
			// Convert milliseconds to time.Time
			t := time.Unix(ts/1000, (ts%1000)*1e6)

			// Parse the value
			var duration int64
			if i < len(result.Values) {
				if f, err := result.Values[i].Int64(); err == nil {
					duration = f
				}
			}

			data := InfluxData{
				Time:     t,
				Duration: duration,
				State:    state,
				Error:    errorMsg,
				Warnings: warnings,
			}
			if data.State == "" {
				data.State = "UNK"
			}
			influxData = append(influxData, data)
		}
	}

	// Sort by time descending (newest first)
	for i := 0; i < len(influxData); i++ {
		for j := i + 1; j < len(influxData); j++ {
			if influxData[i].Time.Before(influxData[j].Time) {
				influxData[i], influxData[j] = influxData[j], influxData[i]
			}
		}
	}

	return influxData, nil
}

// escapeTagValue escapes special characters in influx line protocol tag keys/values.
// Characters that must be escaped: comma, equals, space.
func escapeTagValue(s string) string {
	s = strings.ReplaceAll(s, `\`, `\\`)
	s = strings.ReplaceAll(s, " ", `\ `)
	s = strings.ReplaceAll(s, ",", `\,`)
	s = strings.ReplaceAll(s, "=", `\=`)
	return s
}

// formatInfluxLine formats data as InfluxDB line protocol
func formatInfluxLine(measurement string, tags map[string]string, fields map[string]interface{}, ts time.Time) string {
	var buf bytes.Buffer

	// Write measurement
	buf.WriteString(measurement)

	// Write tags
	tagKeys := make([]string, 0, len(tags))
	for k := range tags {
		tagKeys = append(tagKeys, k)
	}
	// Sort tags for consistency
	for i := 0; i < len(tagKeys); i++ {
		for j := i + 1; j < len(tagKeys); j++ {
			if tagKeys[i] > tagKeys[j] {
				tagKeys[i], tagKeys[j] = tagKeys[j], tagKeys[i]
			}
		}
	}

	for _, k := range tagKeys {
		buf.WriteByte(',')
		buf.WriteString(escapeTagValue(k))
		buf.WriteByte('=')
		buf.WriteString(escapeTagValue(tags[k]))
	}

	buf.WriteByte(' ')

	// Write fields
	fieldKeys := make([]string, 0, len(fields))
	for k := range fields {
		fieldKeys = append(fieldKeys, k)
	}
	firstField := true
	for _, k := range fieldKeys {
		if !firstField {
			buf.WriteByte(',')
		}
		firstField = false
		buf.WriteString(k)
		buf.WriteByte('=')

		switch v := fields[k].(type) {
		case int64:
			buf.WriteString(strconv.FormatInt(v, 10) + "i")
		case int:
			buf.WriteString(strconv.FormatInt(int64(v), 10) + "i")
		case float64:
			buf.WriteString(strconv.FormatFloat(v, 'f', -1, 64))
		case bool:
			if v {
				buf.WriteString("true")
			} else {
				buf.WriteString("false")
			}
		case string:
			buf.WriteByte('"')
			buf.WriteString(strings.ReplaceAll(v, "\"", "\\\""))
			buf.WriteByte('"')
		default:
			buf.WriteString(strconv.FormatFloat(0, 'f', -1, 64))
		}
	}

	// Write timestamp (nanoseconds)
	buf.WriteByte(' ')
	buf.WriteString(strconv.FormatInt(ts.UnixNano(), 10))

	return buf.String()
}

// WriteOne provides functionality.
func WriteOne(metric string, tags map[string]string, fields map[string]interface{}) error {
	ensureInit()
	// Format as InfluxDB line protocol
	line := formatInfluxLine(metric, tags, fields, time.Now())

	// Write to VictoriaMetrics /api/v2/write endpoint
	u, err := url.Parse(addr + "/api/v2/write")
	if err != nil {
		log.Println("TSDB write error (URL parse):", err)
		return err
	}

	req, err := http.NewRequest("POST", u.String(), bytes.NewBufferString(line))
	if err != nil {
		log.Println("TSDB write error (request):", err)
		return err
	}

	req.Header.Set("Content-Type", "text/plain")

	resp, err := client.Do(req)
	if err != nil {
		log.Println("TSDB write error:", err)
		return err
	}
	defer resp.Body.Close() //nolint:errcheck

	if resp.StatusCode != http.StatusNoContent && resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		log.Printf("TSDB write failed with status %d: %s\n", resp.StatusCode, string(body))
		return fmt.Errorf("write failed with status %d", resp.StatusCode)
	}

	return nil
}

// HealthCheck performs a simple health check against VictoriaMetrics
func HealthCheck() error {
	ensureInit()
	u, err := url.Parse(addr + "/health")
	if err != nil {
		return err
	}

	req, err := http.NewRequest("GET", u.String(), http.NoBody)
	if err != nil {
		return err
	}

	resp, err := client.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close() //nolint:errcheck

	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("health check failed with status %d", resp.StatusCode)
	}

	return nil
}

// QueryDB is deprecated and kept for compatibility
// Use QueryVM for MetricsQL queries instead
func QueryDB(query string) ([]VMExportResponse, error) {
	// This is a compatibility function for old code
	// Note: Flux queries are NOT supported by VictoriaMetrics
	// This function tries to do a simple query instead
	log.Println("Warning: QueryDB called with Flux query, VictoriaMetrics uses MetricsQL")
	log.Println("Query:", query)

	// Try a simple health check instead
	return nil, HealthCheck()
}