package main

import (
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/gorilla/mux"
)

// BatteryThresholdsConfig: voltage cutoffs for low-battery alerts (#663).
// All values in millivolts. When a node's most-recent battery sample falls
// below LowMv it is flagged "low"; below CriticalMv it is flagged "critical".
type BatteryThresholdsConfig struct {
	LowMv      int `json:"lowMv"`
	CriticalMv int `json:"criticalMv"`
}

// LowBatteryMv returns the configured low-battery threshold or the default 3300mV.
func (c *Config) LowBatteryMv() int {
	if c.BatteryThresholds != nil && c.BatteryThresholds.LowMv > 0 {
		return c.BatteryThresholds.LowMv
	}
	return 3300
}

// CriticalBatteryMv returns the configured critical-battery threshold or the default 3000mV.
func (c *Config) CriticalBatteryMv() int {
	if c.BatteryThresholds != nil && c.BatteryThresholds.CriticalMv > 0 {
		return c.BatteryThresholds.CriticalMv
	}
	return 3000
}

// NodeBatterySample is a single (timestamp, battery_mv) point.
type NodeBatterySample struct {
	Timestamp string `json:"timestamp"`
	BatteryMv int    `json:"battery_mv"`
}

// GetNodeBatteryHistory returns time-ordered battery_mv samples for a node,
// pulled from observer_metrics by joining observers.id (uppercase pubkey)
// against the node's public_key (lowercase). Rows with NULL battery are skipped.
//
// The match is case-insensitive on observer_id to tolerate historical
// variation in pubkey casing.
func (db *DB) GetNodeBatteryHistory(pubkey, since string) ([]NodeBatterySample, error) {
	if pubkey == "" {
		return nil, nil
	}
	pk := strings.ToLower(pubkey)
	rows, err := db.conn.Query(`
		SELECT timestamp, battery_mv
		FROM observer_metrics
		WHERE LOWER(observer_id) = ?
		  AND battery_mv IS NOT NULL
		  AND timestamp >= ?
		ORDER BY timestamp ASC`, pk, since)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []NodeBatterySample
	for rows.Next() {
		var ts string
		var mv int
		if err := rows.Scan(&ts, &mv); err != nil {
			return nil, err
		}
		out = append(out, NodeBatterySample{Timestamp: ts, BatteryMv: mv})
	}
	return out, rows.Err()
}

// handleNodeBattery serves GET /api/nodes/{pubkey}/battery?days=N (#663).
//
// Returns voltage time-series for a node and a status flag based on the most
// recent sample evaluated against configured thresholds:
//   - "critical" : latest_mv < CriticalBatteryMv
//   - "low"      : latest_mv < LowBatteryMv
//   - "ok"       : latest_mv >= LowBatteryMv
//   - "unknown"  : no samples in window
func (s *Server) handleNodeBattery(w http.ResponseWriter, r *http.Request) {
	pubkey := mux.Vars(r)["pubkey"]
	if pubkey == "" {
		writeError(w, 400, "missing pubkey")
		return
	}

	// 404 if node unknown — keeps URL space tidy and matches /health behavior.
	node, err := s.db.GetNodeByPubkey(pubkey)
	if err != nil {
		writeError(w, 500, err.Error())
		return
	}
	if node == nil {
		writeError(w, 404, "node not found")
		return
	}

	days := 7
	if d, _ := strconv.Atoi(r.URL.Query().Get("days")); d > 0 && d <= 365 {
		days = d
	}
	since := time.Now().UTC().Add(-time.Duration(days) * 24 * time.Hour).Format(time.RFC3339)

	samples, err := s.db.GetNodeBatteryHistory(pubkey, since)
	if err != nil {
		writeError(w, 500, err.Error())
		return
	}
	if samples == nil {
		samples = []NodeBatterySample{}
	}

	low := s.cfg.LowBatteryMv()
	crit := s.cfg.CriticalBatteryMv()

	status := "unknown"
	var latestMv interface{}
	var latestTs interface{}
	if n := len(samples); n > 0 {
		mv := samples[n-1].BatteryMv
		latestMv = mv
		latestTs = samples[n-1].Timestamp
		switch {
		case mv < crit:
			status = "critical"
		case mv < low:
			status = "low"
		default:
			status = "ok"
		}
	}

	writeJSON(w, map[string]interface{}{
		"public_key": strings.ToLower(pubkey),
		"days":       days,
		"samples":    samples,
		"latest_mv":  latestMv,
		"latest_ts":  latestTs,
		"status":     status,
		"thresholds": map[string]interface{}{
			"low_mv":      low,
			"critical_mv": crit,
		},
	})
}