package identity

import (
	"context"
	"database/sql"
	"errors"
	"strings"

	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/envelope"
)

type Resolver interface {
	Resolve(context.Context, envelope.FrameEnvelope) (envelope.FrameEnvelope, error)
}

type NoopResolver struct{}

func (NoopResolver) Resolve(_ context.Context, env envelope.FrameEnvelope) (envelope.FrameEnvelope, error) {
	return env, nil
}

type MySQLResolver struct {
	db    *sql.DB
	table string
}

func NewMySQLResolver(db *sql.DB, table string) *MySQLResolver {
	if db == nil {
		panic("identity db must not be nil")
	}
	table = strings.TrimSpace(table)
	if table == "" || !safeIdentifier(table) {
		table = "vehicle_identity_binding"
	}
	return &MySQLResolver{db: db, table: table}
}

func safeIdentifier(value string) bool {
	if value == "" {
		return false
	}
	for _, r := range value {
		if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') || r == '_' {
			continue
		}
		return false
	}
	return true
}

func (r *MySQLResolver) Resolve(ctx context.Context, env envelope.FrameEnvelope) (envelope.FrameEnvelope, error) {
	if strings.TrimSpace(env.VIN) != "" {
		return env, nil
	}
	candidates := CandidateKeys(env)
	for _, candidate := range candidates {
		vin, err := r.lookup(ctx, candidate.Column, candidate.Value)
		if err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				continue
			}
			return env, err
		}
		if strings.TrimSpace(vin) != "" {
			env.VIN = strings.TrimSpace(vin)
			if env.Parsed == nil {
				env.Parsed = map[string]any{}
			}
			env.Parsed["identity"] = map[string]any{
				"resolved": true,
				"source":   candidate.Column,
				"value":    candidate.Value,
			}
			env.EventID = env.StableEventID()
			return env, nil
		}
	}
	return env, nil
}

func (r *MySQLResolver) lookup(ctx context.Context, column string, value string) (string, error) {
	query := "SELECT vin FROM " + r.table + " WHERE " + column + " = ? AND vin IS NOT NULL AND vin <> '' ORDER BY updated_at DESC LIMIT 1"
	var vin string
	err := r.db.QueryRowContext(ctx, query, value).Scan(&vin)
	return vin, err
}

type CandidateKey struct {
	Column string
	Value  string
}

func CandidateKeys(env envelope.FrameEnvelope) []CandidateKey {
	var out []CandidateKey
	add := func(column string, value string) {
		value = strings.TrimSpace(value)
		if value == "" || strings.EqualFold(value, "unknown") {
			return
		}
		for _, existing := range out {
			if existing.Column == column && existing.Value == value {
				return
			}
		}
		out = append(out, CandidateKey{Column: column, Value: value})
	}
	add("phone", env.Phone)
	if trimmed := strings.TrimLeft(strings.TrimSpace(env.Phone), "0"); trimmed != "" {
		add("phone", trimmed)
	}
	add("device_id", env.DeviceID)
	add("plate", env.Plate)
	add("vin", env.VehicleKeyHint)
	return out
}