package repo

import (
	"context"
	"fmt"
	"time"

	"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"
)

// AnalyticsRepo runs the higher-level P1 query templates (funnel, retention,
// session) against ClickHouse. It shares the read connection with EventRepo
// but lives in its own file because the templates need their own data shapes.
type AnalyticsRepo struct {
	ch  driver.Conn
	tpl *templates.Store
}

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

// ---------------------------------------------------------------------------
// Funnel
// ---------------------------------------------------------------------------

type FunnelQuery struct {
	WorkspaceID   string
	Steps         []string
	From          time.Time
	To            time.Time
	WindowSeconds uint32
}

func (r *AnalyticsRepo) Funnel(ctx context.Context, q FunnelQuery) (*model.QueryResult, error) {
	if len(q.Steps) < 2 {
		return nil, fmt.Errorf("funnel requires at least 2 steps")
	}

	type stepTpl struct {
		Index int
		Last  bool
	}
	stepsTpl := make([]stepTpl, len(q.Steps))
	for i := range q.Steps {
		stepsTpl[i] = stepTpl{Index: i, Last: i == len(q.Steps)-1}
	}

	sql, err := r.tpl.Render("funnel_analysis.sql.tmpl", map[string]any{
		"Steps":     stepsTpl,
		"StepCount": len(q.Steps),
	})
	if err != nil {
		return nil, err
	}

	args := []any{
		clickhouse.Named("workspace_id", q.WorkspaceID),
		clickhouse.Named("from", chTime(q.From)),
		clickhouse.Named("to", chTime(q.To)),
		clickhouse.Named("window_seconds", chUint(uint64(q.WindowSeconds))),
	}
	for i, name := range q.Steps {
		args = append(args, clickhouse.Named(fmt.Sprintf("step%d", i), name))
	}

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

// ---------------------------------------------------------------------------
// Retention
// ---------------------------------------------------------------------------

type RetentionQuery struct {
	WorkspaceID  string
	InitialEvent string
	ReturnEvent  string
	From         time.Time
	To           time.Time
	Periods      int // e.g. 14 => D0..D13
}

func (r *AnalyticsRepo) Retention(ctx context.Context, q RetentionQuery) (*model.QueryResult, error) {
	if q.Periods < 1 {
		q.Periods = 14
	}
	type periodTpl struct {
		RIndex    int
		OffsetDay int
		Last      bool
	}
	outer := make([]periodTpl, q.Periods)
	for i := 0; i < q.Periods; i++ {
		outer[i] = periodTpl{RIndex: i + 2, OffsetDay: i + 1, Last: i == q.Periods-1}
	}

	sql, err := r.tpl.Render("retention_cohort.sql.tmpl", map[string]any{
		"Outer": outer,
	})
	if err != nil {
		return nil, err
	}

	rows, err := r.ch.Query(ctx, sql,
		clickhouse.Named("workspace_id", q.WorkspaceID),
		clickhouse.Named("from", chTime(q.From)),
		clickhouse.Named("to", chTime(q.To)),
		clickhouse.Named("initial_event", q.InitialEvent),
		clickhouse.Named("return_event", q.ReturnEvent),
	)
	if err != nil {
		return nil, fmt.Errorf("clickhouse retention: %w", err)
	}
	defer rows.Close()
	return ScanRows(rows)
}

// ---------------------------------------------------------------------------
// Session
// ---------------------------------------------------------------------------

type SessionQuery struct {
	WorkspaceID    string
	UserID         string // optional
	From           time.Time
	To             time.Time
	TimeoutSeconds uint32
	Limit          int
	Offset         int
}

func (r *AnalyticsRepo) Sessions(ctx context.Context, q SessionQuery) (*model.QueryResult, error) {
	sql, err := r.tpl.Render("session_analysis.sql.tmpl", map[string]any{
		"HasUserID": q.UserID != "",
	})
	if err != nil {
		return nil, err
	}

	args := []any{
		clickhouse.Named("workspace_id", q.WorkspaceID),
		clickhouse.Named("from", chTime(q.From)),
		clickhouse.Named("to", chTime(q.To)),
		clickhouse.Named("timeout_seconds", chUint(uint64(q.TimeoutSeconds))),
		clickhouse.Named("limit", chUint(uint64(q.Limit))),
		clickhouse.Named("offset", chUint(uint64(q.Offset))),
	}
	if q.UserID != "" {
		args = append(args, clickhouse.Named("user_id", q.UserID))
	}

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