package models

import (
	"crypto/rand"
	"crypto/sha256"
	"crypto/subtle"
	"database/sql/driver"
	"encoding/base64"
	"encoding/hex"
	"errors"
	"fmt"
	"sort"
	"strings"
	"time"

	"github.com/lib/pq"
	"gorm.io/datatypes"
	"gorm.io/gorm"

	"rocketgit.ru/rsmon/worker/app/models/concerns"
)

// AccountMCPToken stores a one-way verifier. MCP tokens are bearer credentials
// and must remain valid even when the deployment has no encryption key.
type AccountMCPToken struct {
	concerns.Model
	AccountID int64  `gorm:"type:bigint REFERENCES accounts(id) ON DELETE CASCADE;not null;index" json:"account_id"`
	Name      string `gorm:"size:120;not null" json:"name"`
	TokenEnc  string `gorm:"column:token;type:char(64);not null;index" json:"-"`
	Enabled   bool   `gorm:"not null;default:true" json:"enabled"`
	concerns.Timestamped
}

func (AccountMCPToken) TableName() string { return "account_mcp_tokens" }

func (t *AccountMCPToken) SetToken(token string) error {
	sum := sha256.Sum256([]byte(token))
	t.TokenEnc = hex.EncodeToString(sum[:])
	return nil
}

func (t *AccountMCPToken) TokenMatches(token string) bool {
	sum := sha256.Sum256([]byte(token))
	encoded := hex.EncodeToString(sum[:])
	return subtle.ConstantTimeCompare([]byte(t.TokenEnc), []byte(encoded)) == 1
}

func GenerateMCPToken() string {
	return "mcp_" + base64.RawURLEncoding.EncodeToString(concerns.RandomToken(32))
}

// Server health states — worst-of-monitor-states rollup; see
// docs/plans/servers-and-hardware-metrics.md §5.1 for the data model.
const (
	ServerHealthDown    = "down"
	ServerHealthWarn    = "warn"
	ServerHealthUp      = "up"
	ServerHealthPaused  = "paused"
	ServerHealthUnknown = "unknown"
)

// ServerEnvironments is the allow-list for Server.Environment.
// New environments require an explicit edit so they are visible in
// tests.
var ServerEnvironments = []string{"production", "staging", "dev", "test"}

// ServerKind is the rstuff-mirrored lifecycle label for a Server
// (production / staging / old). See
// docs/parity/rstuff-inventory.md §6.1 for the byte-stable mapping.
type ServerKind string

// ServerKind values match rstuff's Server.kind enum exactly.
// New values require adding a Postgres enum value via
// app/models/migrate.go.
const (
	ServerKindProduction ServerKind = "production"
	ServerKindStaging    ServerKind = "staging"
	ServerKindOld        ServerKind = "old"
)

// Scan implements sql.Scanner for ServerKind.
func (k *ServerKind) Scan(src any) error {
	if src == nil {
		*k = ""
		return nil
	}
	switch v := src.(type) {
	case string:
		*k = ServerKind(v)
	case []byte:
		*k = ServerKind(string(v))
	default:
		return fmt.Errorf("server_kind: cannot scan %T", src)
	}
	return nil
}

// Value implements driver.Valuer for ServerKind.
func (k ServerKind) Value() (driver.Value, error) {
	if k == "" {
		return nil, nil
	}
	return string(k), nil
}

// Server represents a customer-facing logical host (e.g. "prod-web-01").
//
// One Server can host many WorkerNodes (HA after a VM migration). Each
// WorkerNode carries a nullable ServerID so legacy "no server assigned"
// rows keep working. The 1:N relation is stored as a nullable FK on
// worker_nodes.server_id. The N:M relation to Monitor is the
// monitor_servers join table. See
// docs/plans/servers-and-hardware-metrics.md §3 for the layer model
// and §5.1 for the schema.
//
// The inventory fields (ExtID, Kind, Token, PriceCents, Comment,
// Meta) are added per docs/plans/inventory-management.md §6.2 so
// rstuff can push the same row in via Valkey Streams and
// deploymentd can authenticate via Token.
type Server struct {
	concerns.Model

	AccountID   int64          `gorm:"type:bigint REFERENCES accounts(id);not null;index" json:"account_id"`
	Account     *Account       `json:"-"`
	Name        string         `gorm:"size:120;not null" json:"name"`
	Slug        string         `gorm:"size:120;not null;index" json:"slug"`
	Description *string        `gorm:"type:text" json:"description"`
	Region      string         `gorm:"size:64;not null;index" json:"region"`
	Environment string         `gorm:"size:32;not null;default:'production'" json:"environment"`
	Tags        pq.StringArray `gorm:"type:varchar(255)[]" json:"tags"`
	Icon        *string        `gorm:"size:16" json:"icon"`
	Color       *string        `gorm:"size:16" json:"color"`
	Paused      bool           `gorm:"not null;default:false" json:"paused"`

	// Inventory fields (rstuff mirror; see inventory-management.md §6.2).
	ExtID *string    `gorm:"size:64" json:"ext_id,omitempty"`
	Kind  ServerKind `gorm:"type:server_kind;not null;default:'production'" json:"kind"`
	// Token is omitted from JSON because it is a bearer credential.
	// Read it back only via /api/v1/servers/:id/token (operator-only)
	// and never echoed in list/show responses.
	Token      *string `gorm:"size:64" json:"-"`
	PriceCents int     `gorm:"not null;default:0" json:"price_cents"`
	Comment    *string `gorm:"type:text" json:"comment,omitempty"`
	// Meta is rstuff-style free-form jsonb; serialized via JSON
	// encoding (gin renders it as a nested object).
	Meta datatypes.JSON `gorm:"type:jsonb;not null;default:'{}'::jsonb" json:"meta"`

	HealthState string     `gorm:"size:16;not null;default:'unknown';index" json:"health_state"`
	LastCheckAt *time.Time `json:"last_check_at"`
	Uptime24h   float64    `gorm:"not null;default:1.0" json:"uptime_24h"`
	Uptime30d   float64    `gorm:"not null;default:1.0" json:"uptime_30d"`

	Monitors []Monitor    `gorm:"many2many:monitor_servers;joinForeignKey:server_id;joinReferences:monitor_id;" json:"monitors,omitempty"`
	Workers  []WorkerNode `gorm:"foreignKey:ServerID" json:"workers,omitempty"`

	concerns.Timestamped
	Audited
}

// TableName provides functionality.
func (Server) TableName() string { return "servers" }

// MonitorServer is the join row for the N:M relation between Monitor and
// Server. One Monitor can be hosted on many Servers (multi-region
// failover); one Server can host many Monitors.
type MonitorServer struct {
	MonitorID int64 `gorm:"type:bigint REFERENCES monitors(id) ON DELETE CASCADE;primaryKey" json:"monitor_id"`
	ServerID  int64 `gorm:"type:bigint REFERENCES servers(id) ON DELETE CASCADE;primaryKey" json:"server_id"`
	Position  int   `gorm:"not null;default:0" json:"position"`
	concerns.Timestamped
}

// TableName provides functionality.
func (MonitorServer) TableName() string { return "monitor_servers" }

// ServerMetric is the last-N-point cache written alongside VictoriaMetrics.
// The full time-series lives in TSDB; Postgres only keeps the most recent
// row per (server, source) for fast health badges and "last seen" cells.
// See docs/plans/servers-and-hardware-metrics.md §5.3.
type ServerMetric struct {
	concerns.Model

	ServerID      int64          `gorm:"type:bigint REFERENCES servers(id) ON DELETE CASCADE;not null;index" json:"server_id"`
	WorkerID      *int64         `gorm:"type:bigint REFERENCES worker_nodes(id) ON DELETE SET NULL" json:"worker_id"`
	Source        string         `gorm:"size:32;not null;default:'worker'" json:"source"`
	CPUPercent    *float64       `json:"cpu_percent"`
	MemUsed       *int64         `json:"mem_used"`
	MemTotal      *int64         `json:"mem_total"`
	DiskUsed      *int64         `json:"disk_used"`
	DiskTotal     *int64         `json:"disk_total"`
	NetRx         *int64         `json:"net_rx"`
	NetTx         *int64         `json:"net_tx"`
	HostUptimeSec *int64         `json:"host_uptime_sec"`
	Load1         *float64       `json:"load1"`
	Load5         *float64       `json:"load5"`
	Load15        *float64       `json:"load15"`
	ProcessCount  *int           `json:"process_count"`
	Processes     datatypes.JSON `gorm:"type:jsonb;not null;default:'[]'::jsonb" json:"processes"`
	Networks      datatypes.JSON `gorm:"type:jsonb;not null;default:'[]'::jsonb" json:"networks"`

	concerns.Timestamped
}

// ServerAlertRule defines one account-owned threshold for a server metric.
// ClearThreshold implements hysteresis: a firing rule only recovers after the
// value drops below it, avoiding alert flapping around Threshold.
type ServerAlertRule struct {
	concerns.Model
	AccountID      int64      `gorm:"type:bigint REFERENCES accounts(id) ON DELETE CASCADE;not null;index" json:"account_id"`
	ServerID       int64      `gorm:"type:bigint REFERENCES servers(id) ON DELETE CASCADE;not null;index" json:"server_id"`
	Metric         string     `gorm:"size:32;not null" json:"metric"`
	Threshold      float64    `gorm:"not null" json:"threshold"`
	ClearThreshold float64    `gorm:"not null" json:"clear_threshold"`
	DurationSec    int        `gorm:"not null;default:300" json:"duration_sec"`
	NotificationID int64      `gorm:"type:bigint REFERENCES notifications(id) ON DELETE CASCADE;not null" json:"notification_id"`
	Enabled        bool       `gorm:"not null;default:true" json:"enabled"`
	State          string     `gorm:"size:16;not null;default:'ok'" json:"state"`
	BreachSince    *time.Time `json:"breach_since"`
	LastValue      *float64   `json:"last_value"`
	LastMetricID   *int64     `json:"last_metric_id"`
	LastFiredAt    *time.Time `json:"last_fired_at"`
	concerns.Timestamped
}

func (ServerAlertRule) TableName() string { return "server_alert_rules" }

// ServerAlertEvent is the durable dedupe/audit record for threshold changes.
type ServerAlertEvent struct {
	concerns.Model
	RuleID int64   `gorm:"type:bigint REFERENCES server_alert_rules(id) ON DELETE CASCADE;not null;index" json:"rule_id"`
	State  string  `gorm:"size:16;not null" json:"state"`
	Value  float64 `gorm:"not null" json:"value"`
	concerns.Timestamped
}

func (ServerAlertEvent) TableName() string { return "server_alert_events" }

// TableName provides functionality.
func (ServerMetric) TableName() string { return "server_metrics" }

// ValidateEnvironment returns nil iff env is in the allow list.
func ValidateEnvironment(env string) error {
	for _, e := range ServerEnvironments {
		if env == e {
			return nil
		}
	}
	return errors.New("invalid environment")
}

// Slugify turns a server name into a URL-safe slug.
func Slugify(name string) string {
	slug := strings.ToLower(strings.TrimSpace(name))
	var b strings.Builder
	for _, r := range slug {
		switch {
		case r >= 'a' && r <= 'z', r >= '0' && r <= '9':
			b.WriteRune(r)
		case r == ' ', r == '_', r == '-', r == '.':
			b.WriteByte('-')
		}
	}
	out := strings.Trim(b.String(), "-")
	if out == "" {
		out = "server"
	}
	return out
}

// AssignMonitors replaces the full set of monitors for a server. Saves
// the join table explicitly because gorm:association_autoupdate is
// disabled globally (CLAUDE.md GORM Conventions).
func (s *Server) AssignMonitors(tx *gorm.DB, monitorIDs []uint) error {
	if tx == nil {
		tx = DB()
	}
	if err := tx.Exec("DELETE FROM monitor_servers WHERE server_id = ?", s.ID).Error; err != nil {
		return err
	}
	if len(monitorIDs) == 0 {
		return nil
	}
	seen := make(map[uint]struct{}, len(monitorIDs))
	for i, mid := range monitorIDs {
		if _, ok := seen[mid]; ok {
			continue
		}
		seen[mid] = struct{}{}
		row := MonitorServer{ServerID: s.ID, MonitorID: int64(mid), Position: i}
		if err := tx.Create(&row).Error; err != nil {
			return err
		}
	}
	return nil
}

// RollupHealthState computes the worst-of-monitor-states. Returns one of
// ServerHealth{Down,Warn,Up,Paused,Unknown}.
func (s *Server) RollupHealthState(monitors []Monitor) string {
	if s.Paused {
		return ServerHealthPaused
	}
	if len(monitors) == 0 {
		return ServerHealthUnknown
	}
	allPaused := true
	worst := ServerHealthUp
	for i := range monitors {
		m := &monitors[i]
		if m.Enabled {
			allPaused = false
		}
		switch m.State {
		case stateERR, stateFail:
			return ServerHealthDown
		case stateWARN:
			worst = ServerHealthWarn
		}
	}
	if allPaused {
		return ServerHealthPaused
	}
	return worst
}

// SortedTagList returns tags sorted ascending; helper for stable JSON.
func (s *Server) SortedTagList() []string {
	out := make([]string, len(s.Tags))
	copy(out, s.Tags)
	sort.Strings(out)
	return out
}

// HealthForServer recomputes and persists health_state + last_check_at
// for one server. Called by the distworker health ticker.
func HealthForServer(serverID int64) error {
	server := Server{}
	if err := DB().First(&server, serverID).Error; err != nil {
		return err
	}
	var monitors []Monitor
	if err := DB().Joins("JOIN monitor_servers ms ON ms.monitor_id = monitors.id").
		Where("ms.server_id = ?", serverID).Find(&monitors).Error; err != nil {
		return err
	}
	state := server.RollupHealthState(monitors)
	now := time.Now()
	updates := map[string]interface{}{"health_state": state}
	if len(monitors) > 0 {
		updates["last_check_at"] = &now
	}
	return DB().Model(&server).Updates(updates).Error
}

// LatestServerMetric returns the newest accepted worker snapshot for a server.
func LatestServerMetric(serverID int64) (*ServerMetric, error) {
	metric := ServerMetric{}
	err := DB().Where("server_id = ?", serverID).Order("id DESC").First(&metric).Error
	if err != nil {
		return nil, err
	}
	return &metric, nil
}

// FindServerByToken returns the Server whose token column equals
// the given hex value, or nil with gorm.ErrRecordNotFound when no
// row matches. Used by the deploymentd receiver middleware.
func FindServerByToken(token string) (*Server, error) {
	var s Server
	err := DB().Where("token = ?", token).First(&s).Error
	if err != nil {
		return nil, err
	}
	return &s, nil
}

// GenerateServerToken returns a 32-byte random hex string. Caller
// stores the plaintext exactly once (via /servers/:id/rotate-token)
// and updates Server.Token; the old value is no longer recoverable.
func GenerateServerToken() string {
	b := make([]byte, 32)
	if _, err := rand.Read(b); err != nil {
		// crypto/rand should not fail on Linux; panic keeps the
		// contract simple for callers in the rare fatal case.
		panic(err)
	}
	return hex.EncodeToString(b)
}