package db

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

	"vctp/db/queries"

	"github.com/jmoiron/sqlx"
)

// SnapshotTotals summarizes counts and allocations for snapshot tables.
type SnapshotTotals struct {
	VmCount   int64   `db:"vm_count"`
	VcpuTotal int64   `db:"vcpu_total"`
	RamTotal  int64   `db:"ram_total"`
	DiskTotal float64 `db:"disk_total"`
}

// ValidateTableName ensures table identifiers are safe for interpolation.
func ValidateTableName(name string) error {
	if name == "" {
		return fmt.Errorf("table name is empty")
	}
	for _, r := range name {
		if (r >= 'a' && r <= 'z') || (r >= '0' && r <= '9') || r == '_' {
			continue
		}
		return fmt.Errorf("invalid table name: %s", name)
	}
	return nil
}

// SafeTableName returns the name if it passes validation.
func SafeTableName(name string) (string, error) {
	if err := ValidateTableName(name); err != nil {
		return "", err
	}
	return name, nil
}

// TableHasRows returns true when a table contains at least one row.
func TableHasRows(ctx context.Context, dbConn *sqlx.DB, table string) (bool, error) {
	if err := ValidateTableName(table); err != nil {
		return false, err
	}
	query := fmt.Sprintf(`SELECT 1 FROM %s LIMIT 1`, table)
	var exists int
	if err := dbConn.GetContext(ctx, &exists, query); err != nil {
		if err == sql.ErrNoRows {
			return false, nil
		}
		return false, err
	}
	return true, nil
}

// TableExists checks if a table exists in the current schema.
func TableExists(ctx context.Context, dbConn *sqlx.DB, table string) bool {
	driver := strings.ToLower(dbConn.DriverName())
	switch driver {
	case "sqlite":
		q := queries.New(dbConn)
		count, err := q.SqliteTableExists(ctx, sql.NullString{String: table, Valid: table != ""})
		return err == nil && count > 0
	case "pgx", "postgres":
		var count int
		err := dbConn.GetContext(ctx, &count, `
SELECT COUNT(1)
FROM pg_catalog.pg_tables
WHERE schemaname = 'public' AND tablename = $1
`, table)
		return err == nil && count > 0
	default:
		return false
	}
}

// ColumnExists checks if a column exists in a table.
func ColumnExists(ctx context.Context, dbConn *sqlx.DB, tableName string, columnName string) (bool, error) {
	driver := strings.ToLower(dbConn.DriverName())
	switch driver {
	case "sqlite":
		if _, err := SafeTableName(tableName); err != nil {
			return false, err
		}
		query := fmt.Sprintf(`PRAGMA table_info("%s")`, tableName)
		rows, err := dbConn.QueryxContext(ctx, query)
		if err != nil {
			return false, err
		}
		defer rows.Close()
		for rows.Next() {
			var (
				cid        int
				name       string
				colType    string
				notNull    int
				defaultVal sql.NullString
				pk         int
			)
			if err := rows.Scan(&cid, &name, &colType, &notNull, &defaultVal, &pk); err != nil {
				return false, err
			}
			if strings.EqualFold(name, columnName) {
				return true, nil
			}
		}
		return false, rows.Err()
	case "pgx", "postgres":
		var count int
		err := dbConn.GetContext(ctx, &count, `
SELECT COUNT(1)
FROM information_schema.columns
WHERE table_name = $1 AND column_name = $2
`, tableName, strings.ToLower(columnName))
		if err != nil {
			return false, err
		}
		return count > 0, nil
	default:
		return false, fmt.Errorf("unsupported driver for column lookup: %s", driver)
	}
}

// SnapshotTotalsForTable returns totals for a snapshot table.
func SnapshotTotalsForTable(ctx context.Context, dbConn *sqlx.DB, table string) (SnapshotTotals, error) {
	if _, err := SafeTableName(table); err != nil {
		return SnapshotTotals{}, err
	}
	query := fmt.Sprintf(`
SELECT
  COUNT(DISTINCT "VmId") AS vm_count,
  COALESCE(SUM(CASE WHEN "VcpuCount" IS NOT NULL THEN "VcpuCount" ELSE 0 END), 0) AS vcpu_total,
  COALESCE(SUM(CASE WHEN "RamGB" IS NOT NULL THEN "RamGB" ELSE 0 END), 0) AS ram_total,
  COALESCE(SUM(CASE WHEN "ProvisionedDisk" IS NOT NULL THEN "ProvisionedDisk" ELSE 0 END), 0) AS disk_total
FROM %s
WHERE "IsPresent" = 'TRUE'
`, table)

	var totals SnapshotTotals
	if err := dbConn.GetContext(ctx, &totals, query); err != nil {
		return SnapshotTotals{}, err
	}
	return totals, nil
}

// SnapshotTotalsForUnion returns totals for a union query of snapshots.
func SnapshotTotalsForUnion(ctx context.Context, dbConn *sqlx.DB, unionQuery string) (SnapshotTotals, error) {
	query := fmt.Sprintf(`
SELECT
  COUNT(DISTINCT "VmId") AS vm_count,
  COALESCE(SUM(CASE WHEN "VcpuCount" IS NOT NULL THEN "VcpuCount" ELSE 0 END), 0) AS vcpu_total,
  COALESCE(SUM(CASE WHEN "RamGB" IS NOT NULL THEN "RamGB" ELSE 0 END), 0) AS ram_total,
  COALESCE(SUM(CASE WHEN "ProvisionedDisk" IS NOT NULL THEN "ProvisionedDisk" ELSE 0 END), 0) AS disk_total
FROM (
%s
) snapshots
WHERE "IsPresent" = 'TRUE'
`, unionQuery)

	var totals SnapshotTotals
	if err := dbConn.GetContext(ctx, &totals, query); err != nil {
		return SnapshotTotals{}, err
	}
	return totals, nil
}