// file_delete removes a saved file by its file_id. Decrements the
// underlying blob's refcount in storage; the blob row is removed when
// refcount hits zero.
//
// Why scope is checked POST-fetch (mirrors file_get): file_id is the
// only key the caller has; we must read the row to know the scope.
package tools

import (
	"context"
	"errors"
	"fmt"

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

type fileDeleteArgs struct {
	FileID string `json:"file_id" description:"Opaque file ID returned by file_save or file_list."`
}

// NewFileDelete constructs the file_delete tool. storage nil → "not
// configured" at execute time.
func NewFileDelete(storage FileStorage) tool.Tool {
	return tool.NewGatedTool[fileDeleteArgs](
		"file_delete",
		"Remove a saved file by file_id. Returns 'ok' on success or 'not_found' if no file matched.",
		tool.Permission{
			AuthoringRequirement: tool.RequirementAnyone,
			OperatesOn:           tool.ScopeCaller,
			SafeForShare:         true,
			Categories:           []string{"storage", "write"},
		},
		func(ctx context.Context, inv tool.Invocation, args fileDeleteArgs) (string, error) {
			if storage == nil {
				return "", fmt.Errorf("file_delete: not configured")
			}
			if args.FileID == "" {
				return "", fmt.Errorf("file_delete: file_id required")
			}

			// Fetch first so we can validate scope before deleting. The
			// extra read is acceptable for a write path that's not in
			// the hot loop, and it preserves the cross-skill /
			// cross-user safety story.
			meta, _, err := storage.FileGet(ctx, args.FileID)
			if err != nil {
				if errors.Is(err, ErrFileNotFound) {
					return "not_found", nil
				}
				return "", fmt.Errorf("file_delete: %w", err)
			}
			// Honor the descendant grant like the read tools do, so a parent
			// orchestrator can clean up a worker's artifacts (gadfly flagged the
			// asymmetry: delete previously rejected cross-skill outright).
			grantedViaDescendant := false
			if meta.SkillID != inv.SkillID {
				if !descendantFileGrant(ctx, storage, inv, meta.SkillID) {
					return "", fmt.Errorf("file_delete: file does not belong to this skill")
				}
				grantedViaDescendant = true
			}
			if !grantedViaDescendant {
				if err := ValidateScope(inv, meta.Scope, inv.CallerIsAdmin); err != nil {
					return "", fmt.Errorf("file_delete: %w", err)
				}
			}

			if err := storage.FileDelete(ctx, args.FileID); err != nil {
				if errors.Is(err, ErrFileNotFound) {
					// Race: row was deleted between FileGet and
					// FileDelete. Surface as a clean miss.
					return "not_found", nil
				}
				return "", fmt.Errorf("file_delete: %w", err)
			}
			return "ok", nil
		},
	)
}