// kv_set is the v4 KV-storage write tool. It upserts (scope, key) →
// value within the calling skill's namespace, with optional TTL.
//
// Per-value cap: the constructor takes maxValueBytes (typically read
// from convar `skills.storage.kv_max_value_bytes`); 0 means use the
// 64 KiB default.
//
// Per-skill quota (sum across all rows): the constructor's QuotaProvider
// arg drives the v4 Phase 4 enforcement. nil disables enforcement
// (useful for tests and admin-only deployments). The check is:
//
//	used := storage.KVUsageBytes(skill)
//	delta := len(new value) - len(prior value if updating same key)
//	if used + delta > kvMax → quota_exceeded
//
// We subtract the existing value's size on UPDATE so an in-place edit
// of a hot key never trips the cap unless the new value is larger.
package tools

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"gitea.stevedudenhoeffer.com/steve/executus/tool"
)

const defaultKVMaxValueBytes = 65536 // 64 KiB

type kvSetArgs struct {
	Scope      string          `json:"scope" description:"Storage scope: 'skill', 'user:<your_id>', 'run:<run_id>', or 'root_run:<root_run_id>' (shared across the whole dispatch tree)."`
	Key        string          `json:"key" description:"Key within the scope."`
	Value      json.RawMessage `json:"value" description:"JSON value to store. Must parse as valid JSON (object, array, string, number, bool, or null)."`
	TTLSeconds *int            `json:"ttl_seconds,omitempty" description:"Optional TTL in seconds. The entry expires (and is lazy-purged on read) after this duration."`
}

// NewKVSet constructs the kv_set tool.
//
// storage nil → "not configured" at execute time.
// maxValueBytes <= 0 falls back to defaultKVMaxValueBytes.
// quota nil → per-skill quota check is skipped (per-value cap still
// applies).
func NewKVSet(storage KVStorage, quota QuotaProvider, maxValueBytes int) tool.Tool {
	if maxValueBytes <= 0 {
		maxValueBytes = defaultKVMaxValueBytes
	}
	return tool.NewGatedTool[kvSetArgs](
		"kv_set",
		"Set a value at the given scope+key. Optionally with a TTL after which the entry auto-expires.",
		tool.Permission{
			AuthoringRequirement: tool.RequirementAnyone,
			OperatesOn:           tool.ScopeCaller,
			SafeForShare:         true,
			Categories:           []string{"storage", "write"},
		},
		func(ctx context.Context, inv tool.Invocation, args kvSetArgs) (string, error) {
			if storage == nil {
				return "", fmt.Errorf("kv_set: not configured")
			}
			if err := ValidateScope(inv, args.Scope, false); err != nil {
				return "", fmt.Errorf("kv_set: %w", err)
			}
			if args.Key == "" {
				return "", fmt.Errorf("kv_set: key required")
			}
			if len(args.Value) == 0 {
				return "", fmt.Errorf("kv_set: value required")
			}
			if len(args.Value) > maxValueBytes {
				return "", fmt.Errorf("kv_set: value exceeds max %d bytes (got %d)", maxValueBytes, len(args.Value))
			}

			// Validate JSON. The storage layer treats the raw bytes as
			// opaque, but the LLM contract says "value is a JSON value"
			// — surfacing a parse error here gives a friendlier message
			// than letting an invalid blob round-trip and confuse the
			// reader on a future kv_get.
			var probe any
			if err := json.Unmarshal(args.Value, &probe); err != nil {
				return "", fmt.Errorf("kv_set: value is not valid JSON: %w", err)
			}

			partition := kvPartition(inv, args.Scope)

			// Per-skill quota gate (v4 Phase 4). Skipped when quota is nil
			// (tests / admin opt-out) so the per-value cap above is the
			// only line of defence in that mode. Also skipped for the
			// shared root_run partition — per-skill quota attribution is
			// meaningless across the sentinel; the per-value cap above +
			// the run-scope sweeper bound that partition's growth.
			if quota != nil && partition == inv.SkillID {
				kvMax, _, err := quota.EffectiveQuota(ctx, inv.SkillID)
				if err != nil {
					return "", fmt.Errorf("kv_set: quota lookup: %w", err)
				}
				used, err := storage.KVUsageBytes(ctx, inv.SkillID)
				if err != nil {
					return "", fmt.Errorf("kv_set: usage check: %w", err)
				}
				delta := int64(len(args.Value))
				// On UPDATE, subtract the prior value's size so an
				// in-place edit of a hot key doesn't double-count. A
				// brand-new key (KVGet returns ErrKVNotFound) leaves
				// delta untouched.
				if existing, getErr := storage.KVGet(ctx, inv.SkillID, args.Scope, args.Key); getErr == nil && existing != nil {
					delta -= int64(len(existing.Value))
				} else if getErr != nil && !errors.Is(getErr, ErrKVNotFound) {
					return "", fmt.Errorf("kv_set: pre-write lookup: %w", getErr)
				}
				if used+delta > kvMax {
					return "", fmt.Errorf("kv_set: quota_exceeded — %d/%d bytes used; ask admin for higher quota", used, kvMax)
				}
			}

			now := time.Now()
			entry := KVDomainEntry{
				SkillID:   partition,
				Scope:     args.Scope,
				Key:       args.Key,
				Value:     args.Value,
				CreatedAt: now,
				UpdatedAt: now,
			}
			if args.TTLSeconds != nil && *args.TTLSeconds > 0 {
				expires := now.Add(time.Duration(*args.TTLSeconds) * time.Second)
				entry.ExpiresAt = &expires
			}

			if err := storage.KVSet(ctx, entry); err != nil {
				return "", fmt.Errorf("kv_set: %w", err)
			}
			// V7 versioned KV history (admin diagnostic). Best-effort —
			// a failed history write must NOT shadow the successful
			// kv_set return, so we ignore the error after logging.
			// Production adapter satisfies KVHistoryRecorder; tests
			// using a bare KVStorage skip this branch entirely.
			if h, ok := storage.(KVHistoryRecorder); ok && h != nil {
				_ = h.RecordKVHistory(ctx, partition, args.Scope, args.Key, []byte(args.Value), inv.CallerID)
			}
			return "ok", nil
		},
	)
}