package repo

import (
	"context"
	"fmt"

	"github.com/ClickHouse/clickhouse-go/v2"
	"github.com/ClickHouse/clickhouse-go/v2/lib/driver"

	"github.com/dbiz/cdp/data-layer/api/internal/model"
	"github.com/dbiz/cdp/data-layer/api/internal/templates"
)

type EventRepo struct {
	ch  driver.Conn
	tpl *templates.Store
}

func NewEventRepo(ch driver.Conn, tpl *templates.Store) *EventRepo {
	return &EventRepo{ch: ch, tpl: tpl}
}

// QueryEvents renders the event_explorer template against q.Table and returns
// columns+rows. The query is parameterized -- user input never lands in the
// SQL string, only in clickhouse.Named bindings.
func (r *EventRepo) QueryEvents(ctx context.Context, q model.EventQuery) (*model.QueryResult, error) {
	if !q.Table.Valid() {
		return nil, fmt.Errorf("invalid event table: %q", q.Table)
	}
	sql, err := r.tpl.Render("event_explorer.sql.tmpl", map[string]any{
		"Table":          string(q.Table),
		"HasUserID":      q.UserID != "",
		"HasAnonymousID": q.AnonymousID != "",
		"HasEventName":   q.EventName != "" && q.Table == model.EventTableTrack,
	})
	if err != nil {
		return nil, err
	}

	args := []any{
		clickhouse.Named("workspace_id", q.WorkspaceID),
		clickhouse.DateNamed("from", q.From, clickhouse.MilliSeconds),
		clickhouse.DateNamed("to", q.To, clickhouse.MilliSeconds),
		clickhouse.Named("limit", uint32(q.Limit)),
		clickhouse.Named("offset", uint32(q.Offset)),
	}
	if q.UserID != "" {
		args = append(args, clickhouse.Named("user_id", q.UserID))
	}
	if q.AnonymousID != "" {
		args = append(args, clickhouse.Named("anonymous_id", q.AnonymousID))
	}
	if q.EventName != "" && q.Table == model.EventTableTrack {
		args = append(args, clickhouse.Named("event", q.EventName))
	}

	rows, err := r.ch.Query(ctx, sql, args...)
	if err != nil {
		return nil, fmt.Errorf("clickhouse query: %w", err)
	}
	defer rows.Close()

	return ScanRows(rows)
}

// QueryProfileTimeline returns recent events for a profile (resolved to
// user_id) across all four event tables, ordered by received_at desc.
func (r *EventRepo) QueryProfileTimeline(ctx context.Context, workspaceID, userID string, limit, offset int) (*model.QueryResult, error) {
	sql, err := r.tpl.Render("profile_timeline.sql.tmpl", nil)
	if err != nil {
		return nil, err
	}
	rows, err := r.ch.Query(ctx, sql,
		clickhouse.Named("workspace_id", workspaceID),
		clickhouse.Named("user_id", userID),
		clickhouse.Named("limit", uint32(limit)),
		clickhouse.Named("offset", uint32(offset)),
	)
	if err != nil {
		return nil, fmt.Errorf("clickhouse query: %w", err)
	}
	defer rows.Close()
	return ScanRows(rows)
}

// ScanRows turns a driver.Rows iterator into a generic QueryResult. Column
// types come from rows.ColumnTypes() so we allocate the right pointer kinds.
func ScanRows(rows driver.Rows) (*model.QueryResult, error) {
	cols := rows.Columns()
	colTypes := rows.ColumnTypes()
	out := &model.QueryResult{Columns: cols, Rows: [][]any{}}

	for rows.Next() {
		dest := make([]any, len(colTypes))
		for i, ct := range colTypes {
			dest[i] = newScanTarget(ct.ScanType().String())
		}
		if err := rows.Scan(dest...); err != nil {
			return nil, fmt.Errorf("scan row: %w", err)
		}
		row := make([]any, len(dest))
		for i, p := range dest {
			row[i] = derefScanTarget(p)
		}
		out.Rows = append(out.Rows, row)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	out.RowCount = len(out.Rows)
	return out, nil
}

// newScanTarget returns a pointer matching ClickHouse's reported Go scan type.
// We keep this list small -- the analytics tables share a handful of types.
func newScanTarget(typeName string) any {
	switch typeName {
	case "string":
		var v string
		return &v
	case "uint8":
		var v uint8
		return &v
	case "uint16":
		var v uint16
		return &v
	case "uint32":
		var v uint32
		return &v
	case "uint64":
		var v uint64
		return &v
	case "int32":
		var v int32
		return &v
	case "int64":
		var v int64
		return &v
	case "float32":
		var v float32
		return &v
	case "float64":
		var v float64
		return &v
	case "bool":
		var v bool
		return &v
	case "time.Time":
		return new(any) // let driver fill, deref below handles it
	case "map[string]string":
		var v map[string]string
		return &v
	case "[]string":
		var v []string
		return &v
	default:
		// Fallback: untyped pointer; driver decides.
		var v any
		return &v
	}
}

func derefScanTarget(p any) any {
	switch v := p.(type) {
	case *string:
		return *v
	case *uint8:
		return *v
	case *uint16:
		return *v
	case *uint32:
		return *v
	case *uint64:
		return *v
	case *int32:
		return *v
	case *int64:
		return *v
	case *float32:
		return *v
	case *float64:
		return *v
	case *bool:
		return *v
	case *map[string]string:
		return *v
	case *[]string:
		return *v
	case *any:
		return *v
	default:
		return v
	}
}