package tasks

import (
	"context"
	"fmt"
	"log/slog"
	"time"
	"vctp/db"
	"vctp/internal/metrics"
	"vctp/internal/report"
)

// RunVcenterDailyAggregate summarizes hourly snapshots into a daily summary table.
func (c *CronTask) RunVcenterDailyAggregate(ctx context.Context, logger *slog.Logger) (err error) {
	jobTimeout := durationFromSeconds(c.Settings.Values.Settings.DailyJobTimeoutSeconds, 15*time.Minute)
	return c.runAggregateJob(ctx, "daily_aggregate", jobTimeout, func(jobCtx context.Context) error {
		startedAt := time.Now()
		defer func() {
			logger.Info("Daily summary job finished", "duration", time.Since(startedAt))
		}()
		targetTime := time.Now().Add(-time.Minute)
		return c.aggregateDailySummary(jobCtx, targetTime, false)
	})
}

func (c *CronTask) AggregateDailySummary(ctx context.Context, date time.Time, force bool) error {
	return c.aggregateDailySummary(ctx, date, force)
}

func (c *CronTask) aggregateDailySummary(ctx context.Context, targetTime time.Time, force bool) error {
	jobStart := time.Now()
	dayStart := time.Date(targetTime.Year(), targetTime.Month(), targetTime.Day(), 0, 0, 0, 0, targetTime.Location())
	dayEnd := dayStart.AddDate(0, 0, 1)
	summaryTable, err := dailySummaryTableName(targetTime)
	if err != nil {
		return err
	}

	dbConn := c.Database.DB()
	if err := db.EnsureSummaryTable(ctx, dbConn, summaryTable); err != nil {
		return err
	}
	if err := report.EnsureSnapshotRegistry(ctx, c.Database); err != nil {
		return err
	}
	if rowsExist, err := db.TableHasRows(ctx, dbConn, summaryTable); err != nil {
		return err
	} else if rowsExist && !force {
		c.Logger.Debug("Daily summary already exists, skipping aggregation", "summary_table", summaryTable)
		return nil
	} else if rowsExist && force {
		if err := clearTable(ctx, dbConn, summaryTable); err != nil {
			return err
		}
	}

	hourlySnapshots, err := report.SnapshotRecordsWithFallback(ctx, c.Database, "hourly", "inventory_hourly_", "epoch", dayStart, dayEnd)
	if err != nil {
		return err
	}
	hourlySnapshots = filterRecordsInRange(hourlySnapshots, dayStart, dayEnd)
	hourlySnapshots = filterSnapshotsWithRows(ctx, dbConn, hourlySnapshots)
	if len(hourlySnapshots) == 0 {
		return fmt.Errorf("no hourly snapshot tables found for %s", dayStart.Format("2006-01-02"))
	}

	hourlyTables := make([]string, 0, len(hourlySnapshots))
	for _, snapshot := range hourlySnapshots {
		hourlyTables = append(hourlyTables, snapshot.TableName)
		// Ensure indexes exist on historical hourly tables for faster aggregation.
		if err := db.EnsureSnapshotIndexes(ctx, dbConn, snapshot.TableName); err != nil {
			c.Logger.Warn("failed to ensure indexes on hourly table", "table", snapshot.TableName, "error", err)
		}
	}
	unionQuery, err := buildUnionQuery(hourlyTables, summaryUnionColumns, templateExclusionFilter())
	if err != nil {
		return err
	}

	currentTotals, err := db.SnapshotTotalsForUnion(ctx, dbConn, unionQuery)
	if err != nil {
		c.Logger.Warn("unable to calculate daily totals", "error", err, "date", dayStart.Format("2006-01-02"))
	} else {
		c.Logger.Info("Daily snapshot totals",
			"date", dayStart.Format("2006-01-02"),
			"vm_count", currentTotals.VmCount,
			"vcpu_total", currentTotals.VcpuTotal,
			"ram_total_gb", currentTotals.RamTotal,
			"disk_total_gb", currentTotals.DiskTotal,
		)
	}

	prevStart := dayStart.AddDate(0, 0, -1)
	prevEnd := dayStart
	prevSnapshots, err := report.SnapshotRecordsWithFallback(ctx, c.Database, "hourly", "inventory_hourly_", "epoch", prevStart, prevEnd)
	if err == nil && len(prevSnapshots) > 0 {
		prevSnapshots = filterRecordsInRange(prevSnapshots, prevStart, prevEnd)
		prevSnapshots = filterSnapshotsWithRows(ctx, dbConn, prevSnapshots)
		prevTables := make([]string, 0, len(prevSnapshots))
		for _, snapshot := range prevSnapshots {
			prevTables = append(prevTables, snapshot.TableName)
		}
		prevUnion, err := buildUnionQuery(prevTables, summaryUnionColumns, templateExclusionFilter())
		if err == nil {
			prevTotals, err := db.SnapshotTotalsForUnion(ctx, dbConn, prevUnion)
			if err != nil {
				c.Logger.Warn("unable to calculate previous day totals", "error", err, "date", prevStart.Format("2006-01-02"))
			} else {
				c.Logger.Info("Daily snapshot comparison",
					"current_date", dayStart.Format("2006-01-02"),
					"previous_date", prevStart.Format("2006-01-02"),
					"vm_delta", currentTotals.VmCount-prevTotals.VmCount,
					"vcpu_delta", currentTotals.VcpuTotal-prevTotals.VcpuTotal,
					"ram_delta_gb", currentTotals.RamTotal-prevTotals.RamTotal,
					"disk_delta_gb", currentTotals.DiskTotal-prevTotals.DiskTotal,
				)
			}
		} else {
			c.Logger.Warn("unable to build previous day union", "error", err)
		}
	}

	insertQuery, err := db.BuildDailySummaryInsert(summaryTable, unionQuery)
	if err != nil {
		return err
	}

	if _, err := dbConn.ExecContext(ctx, insertQuery); err != nil {
		c.Logger.Error("failed to aggregate daily inventory", "error", err, "date", dayStart.Format("2006-01-02"))
		return err
	}
	// Backfill missing creation times to the start of the day for rows where vCenter had no creation info.
	if _, err := dbConn.ExecContext(ctx,
		`UPDATE `+summaryTable+` SET "CreationTime" = $1 WHERE "CreationTime" IS NULL OR "CreationTime" = 0`,
		dayStart.Unix(),
	); err != nil {
		c.Logger.Warn("failed to normalize creation times for daily summary", "error", err, "table", summaryTable)
	}
	if err := db.RefineCreationDeletionFromUnion(ctx, dbConn, summaryTable, unionQuery); err != nil {
		c.Logger.Warn("failed to refine creation/deletion times", "error", err, "table", summaryTable)
	}
	rowCount, err := db.TableRowCount(ctx, dbConn, summaryTable)
	if err != nil {
		c.Logger.Warn("unable to count daily summary rows", "error", err, "table", summaryTable)
	}
	if err := report.RegisterSnapshot(ctx, c.Database, "daily", summaryTable, dayStart, rowCount); err != nil {
		c.Logger.Warn("failed to register daily snapshot", "error", err, "table", summaryTable)
	}

	if err := c.generateReport(ctx, summaryTable); err != nil {
		c.Logger.Warn("failed to generate daily report", "error", err, "table", summaryTable)
		metrics.RecordDailyAggregation(time.Since(jobStart), err)
		return err
	}

	c.Logger.Debug("Finished daily inventory aggregation", "summary_table", summaryTable)
	metrics.RecordDailyAggregation(time.Since(jobStart), nil)
	return nil
}

func dailySummaryTableName(t time.Time) (string, error) {
	return db.SafeTableName(fmt.Sprintf("inventory_daily_summary_%s", t.Format("20060102")))
}