// SPDX-FileCopyrightText: 2026 Kaede Akino
// SPDX-License-Identifier: GPL-3.0-only

import AgentKit
import Foundation
import SwiftData
import TermindApplication

/// Local storage for the skill library.
///
/// Delete-and-rewrite, following `AIPersistence.save`: the library is a short,
/// wholly-owned list, and a diff would be more code to get wrong than the write
/// it saves. Its own store rather than a fourth field on the AI snapshot, so
/// editing one skill does not rewrite every provider and model row.
@MainActor
public final class SkillPersistence {
    private let context: ModelContext

    public init(context: ModelContext) {
        self.context = context
    }

    public func load() throws -> [AgentSkill] {
        let rows = try context.fetch(
            FetchDescriptor<PersistentAgentSkill>(sortBy: [SortDescriptor(\.sortIndex)])
        )
        let packages = try context.fetch(FetchDescriptor<PersistentSkillPackage>())
        var byID: [UUID: AgentSkillPackage] = [:]
        for package in packages { byID[package.skillID] = try package.value() }
        var seen: Set<UUID> = []
        return rows.compactMap { row in
            guard seen.insert(row.id).inserted else { return nil }
            var value = row.value
            value.package = byID[row.id]
            return value
        }
    }

    public func save(_ skills: [AgentSkill]) throws {
        try context.commit { try replace(skills) }
    }

    /// Stages rows in the caller-owned transaction.
    public func replace(_ skills: [AgentSkill]) throws {
        try context.delete(model: PersistentAgentSkill.self)
        try context.delete(model: PersistentSkillPackage.self)
        for (index, skill) in skills.enumerated() {
            context.insert(PersistentAgentSkill(skill, sortIndex: index))
            if let package = skill.package {
                try package.validate()
                context.insert(try PersistentSkillPackage(skillID: skill.id, package: package))
            }
        }
    }
}

extension SkillPersistence: SkillLibraryPersisting {}