package scheduler

import (
	"context"
	"encoding/json"
	"fmt"
	"strconv"
	"strings"
	"time"

	"github.com/dtoro/oikos/internal/db/sqlcgen"
)

// checkBackupFreshness reports whether a backup target has a recent artifact.
//
// The ontology has carried a `backup-target` type and a `backs-up-to` edge
// since the first seed, but nothing ever verified that a backup actually
// happened — a silent backup failure looked exactly like a working one. This
// makes staleness a Signal like any other, so it flows through the existing
// dedup, auto-resolve and notifier path rather than needing its own machinery.
//
// Config: {"path": "/opt/oikos/backups", "max_age_s": 86400, "host": …}
//
// Deliberately uses `find -mmin` rather than `-printf '%T@'` or `stat`:
// -printf is GNU-only and stat's format flag differs between GNU (-c) and BSD
// (-f). The first real target for this check is the pre-deploy pg_dump on the
// mac-mini, which is macOS — so a GNU-only probe would have silently reported
// "unknown" on the one target that motivated the check.
func checkBackupFreshness(ctx context.Context, cd sqlcgen.ListEnabledCheckDefsRow) checkResult {
	cfg := struct {
		Path    string `json:"path"`
		MaxAgeS int    `json:"max_age_s"`
		Host    string `json:"host"`
		User    string `json:"user"`
		Port    int    `json:"port"`
	}{
		MaxAgeS: 86400, // a daily backup that has not run in 24h is stale
	}
	if len(cd.Config) > 0 {
		_ = json.Unmarshal(cd.Config, &cfg)
	}
	if cfg.Path == "" || cfg.Host == "" {
		return checkResult{health: "unknown", signalKind: "backup-misconfigured",
			evidence: "backup check needs both a path and a host"}
	}
	if cfg.Port == 0 {
		cfg.Port = 22
	}
	if cfg.User == "" {
		cfg.User = sshUser
	}
	if cfg.MaxAgeS <= 0 {
		cfg.MaxAgeS = 86400
	}

	timeout := time.Duration(cd.TimeoutS) * time.Second
	if timeout <= 0 {
		timeout = 30 * time.Second
	}
	ctx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()

	minutes := cfg.MaxAgeS / 60
	if minutes < 1 {
		minutes = 1
	}
	quoted := shellSingleQuote(cfg.Path)

	// Two questions in one round trip: is there anything at all, and is any of
	// it recent? "no backups ever" and "backups stopped" are different
	// failures and deserve different severities.
	cmd := fmt.Sprintf(
		`if [ ! -d %s ]; then echo missing; else `+
			`f=$(find %s -type f -mmin -%d 2>/dev/null | head -1); `+
			`a=$(find %s -type f 2>/dev/null | head -1); `+
			`if [ -n "$f" ]; then echo fresh; elif [ -n "$a" ]; then echo stale; else echo empty; fi; fi`,
		quoted, quoted, minutes, quoted)

	out, err := sshExec(ctx, cfg.Host, strconv.Itoa(cfg.Port), cfg.User, cmd, timeout)
	if err != nil {
		return checkResult{
			health: "unknown", signalKind: "backup-unreachable",
			evidence: fmt.Sprintf("ssh %s: %v", cfg.Host, err),
			err:      err,
		}
	}

	age := time.Duration(cfg.MaxAgeS) * time.Second
	switch strings.TrimSpace(string(out)) {
	case "fresh":
		return checkResult{health: "healthy"}
	case "stale":
		return checkResult{
			health: "degraded", signalKind: "backup-stale",
			evidence: fmt.Sprintf("no backup in %s under %s on %s", age, cfg.Path, cfg.Host),
		}
	case "empty":
		return checkResult{
			health: "down", signalKind: "backup-missing",
			evidence: fmt.Sprintf("%s on %s exists but contains no files", cfg.Path, cfg.Host),
		}
	case "missing":
		return checkResult{
			health: "down", signalKind: "backup-missing",
			evidence: fmt.Sprintf("backup directory %s does not exist on %s", cfg.Path, cfg.Host),
		}
	}
	return checkResult{health: "unknown", signalKind: "backup-unreachable",
		evidence: fmt.Sprintf("unexpected probe output: %q", strings.TrimSpace(string(out)))}
}

// shellSingleQuote makes a path safe to embed in the remote sh command. Paths
// come from check_defs config, which an operator or the agent can write.
func shellSingleQuote(s string) string {
	return "'" + strings.ReplaceAll(s, "'", `'\''`) + "'"
}