package gorm_tracing

import (
	"errors"
	"fmt"
	"strings"
	"time"

	"git.ma-al.com/maal-libraries/observer/pkg/attr"
	"git.ma-al.com/maal-libraries/observer/pkg/event"
	"git.ma-al.com/maal-libraries/observer/pkg/level"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	semconv "go.opentelemetry.io/otel/semconv/v1.25.0"
	"go.opentelemetry.io/otel/trace"
	"gorm.io/gorm"
)

type Option func(p *gormPlugin)

func defaultSqlQueryFormatter(query string) string {
	return strings.Join(strings.Fields(strings.TrimSpace(query)), " ")
}

// WithEveryStatementAsEvent configures the plugin to log all statements as distinct events, not just errors and warnings.
func WithEveryStatementAsEvent() Option {
	return func(p *gormPlugin) {
		p.everyStatementAsEvent = true
	}
}

// WithSlowQueryDuration configures the duration at which the query will be considered slow an logged with warning.
func WithSlowQueryDuration(duration time.Duration) Option {
	return func(p *gormPlugin) {
		p.slowQueryDuration = duration
	}
}

// WithTracerProvider configures a tracer provider that is used to create a tracer.
func WithTracerProvider(provider trace.TracerProvider) Option {
	return func(p *gormPlugin) {
		p.provider = provider
	}
}

// WithAttributes configures attributes that are used to create a span.
func WithAttributes(attrs ...attribute.KeyValue) Option {
	return func(p *gormPlugin) {
		p.attrs = append(p.attrs, attrs...)
	}
}

// WithDBName configures a db.name attribute.
func WithDBName(name string) Option {
	return func(p *gormPlugin) {
		p.attrs = append(p.attrs, semconv.DBNameKey.String(name))
	}
}

// WithoutQueryVariables configures the db.statement attribute to exclude query variables
func WithoutQueryVariables() Option {
	return func(p *gormPlugin) {
		p.excludeQueryVars = true
	}
}

// WithQueryFormatter configures a query formatter
func WithQueryFormatter(queryFormatter func(query string) string) Option {
	return func(p *gormPlugin) {
		p.queryFormatter = queryFormatter
	}
}

// WithDefaultQueryFormatter adds a simple formatter that trims any excess whitespaces from the query
func WithDefaultQueryFormatter() Option {
	return func(p *gormPlugin) {
		p.queryFormatter = defaultSqlQueryFormatter
	}
}

type gormPlugin struct {
	provider              trace.TracerProvider
	tracer                trace.Tracer
	attrs                 []attribute.KeyValue
	excludeQueryVars      bool
	queryFormatter        func(query string) string
	slowQueryDuration     time.Duration
	everyStatementAsEvent bool
}

// Overrides and sets some options with recommended defaults
func DefaultGormPlugin(opts ...Option) gorm.Plugin {
	p := &gormPlugin{}
	for _, opt := range opts {
		opt(p)
	}
	WithDefaultQueryFormatter()(p)
	WithoutQueryVariables()(p)
	WithEveryStatementAsEvent()(p)
	p.provider = otel.GetTracerProvider()
	p.tracer = p.provider.Tracer("git.ma-al.com/maal-libraries/observer/pkg/gorm_tracing")
	return p
}

func NewGormPlugin(opts ...Option) gorm.Plugin {
	p := &gormPlugin{}
	for _, opt := range opts {
		opt(p)
	}

	if p.provider == nil {
		p.provider = otel.GetTracerProvider()
	}
	p.tracer = p.provider.Tracer("git.ma-al.com/maal-libraries/observer/pkg/gorm_tracing")

	return p
}

func (p gormPlugin) Name() string {
	return "observerGorm"
}

type gormHookFunc func(tx *gorm.DB)

type gormRegister interface {
	Register(name string, fn func(*gorm.DB)) error
}

func (p gormPlugin) Initialize(db *gorm.DB) (err error) {
	cb := db.Callback()
	hooks := []struct {
		callback gormRegister
		hook     gormHookFunc
		name     string
	}{
		{cb.Create().Before("gorm:create"), p.before("gorm.Create"), "before:create"},
		{cb.Create().After("gorm:create"), p.after(), "after:create"},

		{cb.Query().Before("gorm:query"), p.before("gorm.Query"), "before:select"},
		{cb.Query().After("gorm:query"), p.after(), "after:select"},

		{cb.Delete().Before("gorm:delete"), p.before("gorm.Delete"), "before:delete"},
		{cb.Delete().After("gorm:delete"), p.after(), "after:delete"},

		{cb.Update().Before("gorm:update"), p.before("gorm.Update"), "before:update"},
		{cb.Update().After("gorm:update"), p.after(), "after:update"},

		{cb.Row().Before("gorm:row"), p.before("gorm.Row"), "before:row"},
		{cb.Row().After("gorm:row"), p.after(), "after:row"},

		{cb.Raw().Before("gorm:raw"), p.before("gorm.Raw"), "before:raw"},
		{cb.Raw().After("gorm:raw"), p.after(), "after:raw"},
	}

	var firstErr error

	for _, h := range hooks {
		if err := h.callback.Register("observer:"+h.name, h.hook); err != nil && firstErr == nil {
			firstErr = fmt.Errorf("callback register %s failed: %w", h.name, err)
		}
	}

	return firstErr
}

func (p *gormPlugin) before(spanName string) gormHookFunc {
	return func(tx *gorm.DB) {
		ctx := tx.Statement.Context

		tx.Statement.Set("observer:statement_start", time.Now())
		tx.Statement.Context, _ = p.tracer.Start(ctx, spanName, trace.WithSpanKind(trace.SpanKindClient))
	}
}

func (p *gormPlugin) after() gormHookFunc {
	return func(tx *gorm.DB) {
		span := trace.SpanFromContext(tx.Statement.Context)
		if !span.IsRecording() {
			return
		}
		defer span.End()

		attrs := make([]attribute.KeyValue, 0, len(p.attrs)+4)
		attrs = append(attrs, p.attrs...)

		if sys := dbSystem(tx); sys.Valid() {
			attrs = append(attrs, sys)
		}

		vars := tx.Statement.Vars
		if p.excludeQueryVars {
			// Replace query variables with '?' to mask them
			vars = make([]interface{}, len(tx.Statement.Vars))

			for i := 0; i < len(vars); i++ {
				vars[i] = "?"
			}
		}

		query := tx.Dialector.Explain(tx.Statement.SQL.String(), vars...)

		attrs = append(attrs, semconv.DBStatementKey.String(p.formatQuery(query)))
		if tx.Statement.Table != "" {
			attrs = append(attrs, semconv.DBSQLTableKey.String(tx.Statement.Table))
		}
		if tx.Statement.RowsAffected != -1 {
			attrs = append(attrs, attr.DBRowsAffected(tx.Statement.RowsAffected))
		}

		slowQuery := false
		if statementStart, ok := tx.Statement.Get("observer:statement_start"); ok {
			start := statementStart.(time.Time)
			duration := time.Now().Sub(start)

			attrs = append(attrs, attr.DBExecutionTimeMs(duration))

			if p.slowQueryDuration != time.Duration(0) {
				if duration >= p.slowQueryDuration {
					slowQuery = true

					event.NewErrInSpan(event.Error{
						Level:      level.WARN,
						Err:        errors.New("slow query execution"),
						Attributes: attrs,
					}.SkipMoreInCallStack(3), span)

					attrs = append(attrs, attr.SeverityLevel(level.WARN))
				}
			}
		}
		errQuery := false
		if tx.Statement.Error != nil {
			errQuery = true

			event.NewErrInSpan(event.Error{
				Level:      level.ERR,
				Err:        tx.Statement.Error,
				Attributes: attrs,
			}.SkipMoreInCallStack(3), span)

			attrs = append(attrs, attr.SeverityLevel(level.ERR))
		}

		if !slowQuery && !errQuery && p.everyStatementAsEvent {
			event.NewInSpan(event.Event{
				Level:        level.DEBUG,
				ShortMessage: "executed an sql query with gorm",
				Attributes:   attrs,
			}.SkipMoreInCallStack(3), span)

			attrs = append(attrs, attr.SeverityLevel(level.DEBUG))
		}

		span.SetAttributes(attrs...)
	}
}

func (p *gormPlugin) formatQuery(query string) string {
	if p.queryFormatter != nil {
		return p.queryFormatter(query)
	}
	return query
}

func dbSystem(tx *gorm.DB) attribute.KeyValue {
	switch tx.Dialector.Name() {
	case "mysql":
		return semconv.DBSystemMySQL
	case "mssql":
		return semconv.DBSystemMSSQL
	case "postgres", "postgresql":
		return semconv.DBSystemPostgreSQL
	case "sqlite":
		return semconv.DBSystemSqlite
	case "sqlserver":
		return semconv.DBSystemKey.String("sqlserver")
	case "clickhouse":
		return semconv.DBSystemKey.String("clickhouse")
	default:
		return attribute.KeyValue{}
	}
}