// Package scheduler — system_builtins.go
//
// v0.28.6: Built-in system functions registered at startup.
// v0.29.0: Raw SQL replaced with store methods.
package scheduler

import (
	"context"
	"fmt"
	"log"
	"time"

	"git.gobha.me/xcaliber/chat-switchboard/store"
	"git.gobha.me/xcaliber/chat-switchboard/taskutil"
)

// RegisterBuiltins registers all built-in system functions.
func RegisterBuiltins() {
	taskutil.RegisterSystemFunc("session_cleanup",
		"Remove expired anonymous visitor sessions",
		sessionCleanup)

	taskutil.RegisterSystemFunc("staleness_check",
		"Mark idle workflow instances as stale",
		stalenessCheck)

	taskutil.RegisterSystemFunc("retention_sweep",
		"Delete completed workflow instances past retention policy",
		retentionSweep)

	taskutil.RegisterSystemFunc("health_prune",
		"Prune provider health windows older than 7 days",
		healthPrune)
}

// ── session_cleanup ─────────────────────────

func sessionCleanup(ctx context.Context, stores store.Stores) (string, error) {
	if stores.Sessions == nil {
		return "skipped: session store not available", nil
	}
	cutoff := time.Now().UTC().AddDate(0, 0, -7)
	n, err := stores.Sessions.DeleteExpired(ctx, cutoff)
	if err != nil {
		return "", fmt.Errorf("session cleanup failed: %w", err)
	}
	msg := fmt.Sprintf("cleaned up %d expired sessions (cutoff: %s)", n, cutoff.Format(time.RFC3339))
	if n > 0 {
		log.Printf("[system_task] %s", msg)
	}
	return msg, nil
}

// ── staleness_check ─────────────────────────

func stalenessCheck(ctx context.Context, stores store.Stores) (string, error) {
	cutoff := time.Now().UTC().Add(-48 * time.Hour)
	n, err := stores.Channels.MarkStaleWorkflows(ctx, cutoff)
	if err != nil {
		return "", fmt.Errorf("staleness sweep failed: %w", err)
	}
	msg := fmt.Sprintf("marked %d idle workflow instances as stale (cutoff: %s)", n, cutoff.Format(time.RFC3339))
	if n > 0 {
		log.Printf("[system_task] %s", msg)
	}
	return msg, nil
}

// ── retention_sweep ─────────────────────────

func retentionSweep(ctx context.Context, stores store.Stores) (string, error) {
	n, err := stores.Channels.EnforceWorkflowRetention(ctx)
	if err != nil {
		return "", fmt.Errorf("retention enforcement failed: %w", err)
	}
	msg := fmt.Sprintf("deleted %d expired workflow instances (retention policy)", n)
	if n > 0 {
		log.Printf("[system_task] %s", msg)
	}
	return msg, nil
}

// ── health_prune ────────────────────────────

func healthPrune(ctx context.Context, stores store.Stores) (string, error) {
	if stores.Health == nil {
		return "skipped: health store not available", nil
	}
	cutoff := time.Now().UTC().Add(-7 * 24 * time.Hour)
	n, err := stores.Health.Prune(ctx, cutoff)
	if err != nil {
		return "", fmt.Errorf("health prune failed: %w", err)
	}
	msg := fmt.Sprintf("pruned %d old health windows (cutoff: %s)", n, cutoff.Format(time.RFC3339))
	if n > 0 {
		log.Printf("[system_task] %s", msg)
	}
	return msg, nil
}