//
//  Project.swift
//  Focale
//
//  Author: Simon-Pierre Boucher
//  Contact: contact@spboucher.ai
//
//  Project mode: the user declares "chantier cuisine" once, then every
//  photo taken is tagged. One gesture, zero friction afterwards.
//

import Foundation
import Observation

struct Project: Codable, Identifiable, Sendable, Hashable {
    typealias ID = UUID

    let id: ID
    var name: String
    var createdAt: Date
    var endedAt: Date?

    var isActive: Bool { endedAt == nil }

    init(id: ID = UUID(), name: String, createdAt: Date = .now, endedAt: Date? = nil) {
        self.id = id
        self.name = name
        self.createdAt = createdAt
        self.endedAt = endedAt
    }
}

/// Owns the list of projects and the single currently active one.
@MainActor
@Observable
final class ProjectStore {
    private(set) var projects: [Project] = []
    private(set) var activeProjectID: Project.ID?

    private let fileURL: URL

    var activeProject: Project? {
        guard let activeProjectID else { return nil }
        return projects.first { $0.id == activeProjectID }
    }

    init(directory: URL = .applicationSupportDirectory) {
        fileURL = directory.appending(path: "projects.json")
        load()
    }

    /// Declare a new project and make it active immediately.
    @discardableResult
    func declare(_ name: String) -> Project {
        let project = Project(name: name)
        projects.insert(project, at: 0)
        activeProjectID = project.id
        save()
        return project
    }

    func activate(_ id: Project.ID?) {
        activeProjectID = id
        save()
    }

    func end(_ id: Project.ID) {
        guard let index = projects.firstIndex(where: { $0.id == id }) else { return }
        projects[index].endedAt = .now
        if activeProjectID == id { activeProjectID = nil }
        save()
    }

    // MARK: - Persistence

    private struct Snapshot: Codable {
        var projects: [Project]
        var activeProjectID: Project.ID?
    }

    private func load() {
        guard let data = try? Data(contentsOf: fileURL),
              let snapshot = try? JSONDecoder().decode(Snapshot.self, from: data)
        else { return }
        projects = snapshot.projects
        activeProjectID = snapshot.activeProjectID
    }

    private func save() {
        let snapshot = Snapshot(projects: projects, activeProjectID: activeProjectID)
        guard let data = try? JSONEncoder().encode(snapshot) else { return }
        try? FileManager.default.createDirectory(
            at: fileURL.deletingLastPathComponent(),
            withIntermediateDirectories: true
        )
        try? data.write(to: fileURL, options: .atomic)
    }
}