//! Enhanced sharing system.
//!
//! Provides comprehensive sharing capabilities:
//! - Public link sharing with optional password/expiry
//! - User-to-user sharing with granular permissions
//! - Collection/tag sharing with inheritance
//! - Activity logging and notifications

use std::fmt;

use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};
use uuid::Uuid;

use crate::model::MediaId;
use crate::users::UserId;

/// Unique identifier for a share.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub struct ShareId(pub Uuid);

impl ShareId {
    pub fn new() -> Self {
        Self(Uuid::now_v7())
    }
}

impl Default for ShareId {
    fn default() -> Self {
        Self::new()
    }
}

impl fmt::Display for ShareId {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.0)
    }
}

/// What is being shared.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum ShareTarget {
    Media { media_id: MediaId },
    Collection { collection_id: Uuid },
    Tag { tag_id: Uuid },
    SavedSearch { search_id: Uuid },
}

impl ShareTarget {
    pub fn target_type(&self) -> &'static str {
        match self {
            Self::Media { .. } => "media",
            Self::Collection { .. } => "collection",
            Self::Tag { .. } => "tag",
            Self::SavedSearch { .. } => "saved_search",
        }
    }

    pub fn target_id(&self) -> Uuid {
        match self {
            Self::Media { media_id } => media_id.0,
            Self::Collection { collection_id } => *collection_id,
            Self::Tag { tag_id } => *tag_id,
            Self::SavedSearch { search_id } => *search_id,
        }
    }
}

/// Who the share is with.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
pub enum ShareRecipient {
    /// Public link accessible to anyone with the token
    PublicLink {
        token: String,
        password_hash: Option<String>,
    },
    /// Shared with a specific user
    User { user_id: UserId },
    /// Shared with a group
    Group { group_id: Uuid },
    /// Shared with a federated user on another server
    Federated {
        user_handle: String,
        server_url: String,
    },
}

impl ShareRecipient {
    pub fn recipient_type(&self) -> &'static str {
        match self {
            Self::PublicLink { .. } => "public_link",
            Self::User { .. } => "user",
            Self::Group { .. } => "group",
            Self::Federated { .. } => "federated",
        }
    }
}

/// Permissions granted by a share.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq, Serialize, Deserialize)]
pub struct SharePermissions {
    /// Can view the content
    pub can_view: bool,
    /// Can download the content
    pub can_download: bool,
    /// Can edit the content/metadata
    pub can_edit: bool,
    /// Can delete the content
    pub can_delete: bool,
    /// Can reshare with others
    pub can_reshare: bool,
    /// Can add new items (for collections)
    pub can_add: bool,
}

impl SharePermissions {
    /// View-only permissions
    pub fn view_only() -> Self {
        Self {
            can_view: true,
            ..Default::default()
        }
    }

    /// Download permissions (includes view)
    pub fn download() -> Self {
        Self {
            can_view: true,
            can_download: true,
            ..Default::default()
        }
    }

    /// Edit permissions (includes view and download)
    pub fn edit() -> Self {
        Self {
            can_view: true,
            can_download: true,
            can_edit: true,
            can_add: true,
            ..Default::default()
        }
    }

    /// Full permissions
    pub fn full() -> Self {
        Self {
            can_view: true,
            can_download: true,
            can_edit: true,
            can_delete: true,
            can_reshare: true,
            can_add: true,
        }
    }

    /// Merge permissions (takes the most permissive of each)
    pub fn merge(&self, other: &Self) -> Self {
        Self {
            can_view: self.can_view || other.can_view,
            can_download: self.can_download || other.can_download,
            can_edit: self.can_edit || other.can_edit,
            can_delete: self.can_delete || other.can_delete,
            can_reshare: self.can_reshare || other.can_reshare,
            can_add: self.can_add || other.can_add,
        }
    }
}

/// A share record.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Share {
    pub id: ShareId,
    pub target: ShareTarget,
    pub owner_id: UserId,
    pub recipient: ShareRecipient,
    pub permissions: SharePermissions,
    pub note: Option<String>,
    pub expires_at: Option<DateTime<Utc>>,
    pub access_count: u64,
    pub last_accessed: Option<DateTime<Utc>>,
    /// Whether children (media in collection, etc.) inherit this share
    pub inherit_to_children: bool,
    /// Parent share if this was created via reshare
    pub parent_share_id: Option<ShareId>,
    pub created_at: DateTime<Utc>,
    pub updated_at: DateTime<Utc>,
}

impl Share {
    /// Create a new public link share.
    pub fn new_public_link(
        owner_id: UserId,
        target: ShareTarget,
        token: String,
        permissions: SharePermissions,
    ) -> Self {
        let now = Utc::now();
        Self {
            id: ShareId::new(),
            target,
            owner_id,
            recipient: ShareRecipient::PublicLink {
                token,
                password_hash: None,
            },
            permissions,
            note: None,
            expires_at: None,
            access_count: 0,
            last_accessed: None,
            inherit_to_children: true,
            parent_share_id: None,
            created_at: now,
            updated_at: now,
        }
    }

    /// Create a new user share.
    pub fn new_user_share(
        owner_id: UserId,
        target: ShareTarget,
        recipient_user_id: UserId,
        permissions: SharePermissions,
    ) -> Self {
        let now = Utc::now();
        Self {
            id: ShareId::new(),
            target,
            owner_id,
            recipient: ShareRecipient::User {
                user_id: recipient_user_id,
            },
            permissions,
            note: None,
            expires_at: None,
            access_count: 0,
            last_accessed: None,
            inherit_to_children: true,
            parent_share_id: None,
            created_at: now,
            updated_at: now,
        }
    }

    /// Check if the share has expired.
    pub fn is_expired(&self) -> bool {
        self.expires_at.map(|exp| exp < Utc::now()).unwrap_or(false)
    }

    /// Check if this is a public link share.
    pub fn is_public(&self) -> bool {
        matches!(self.recipient, ShareRecipient::PublicLink { .. })
    }

    /// Get the public token if this is a public link share.
    pub fn public_token(&self) -> Option<&str> {
        match &self.recipient {
            ShareRecipient::PublicLink { token, .. } => Some(token),
            _ => None,
        }
    }
}

/// Types of share activity actions.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum ShareActivityAction {
    Created,
    Updated,
    Accessed,
    Downloaded,
    Revoked,
    Expired,
    PasswordFailed,
}

impl fmt::Display for ShareActivityAction {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Created => write!(f, "created"),
            Self::Updated => write!(f, "updated"),
            Self::Accessed => write!(f, "accessed"),
            Self::Downloaded => write!(f, "downloaded"),
            Self::Revoked => write!(f, "revoked"),
            Self::Expired => write!(f, "expired"),
            Self::PasswordFailed => write!(f, "password_failed"),
        }
    }
}

impl std::str::FromStr for ShareActivityAction {
    type Err = String;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s.to_lowercase().as_str() {
            "created" => Ok(Self::Created),
            "updated" => Ok(Self::Updated),
            "accessed" => Ok(Self::Accessed),
            "downloaded" => Ok(Self::Downloaded),
            "revoked" => Ok(Self::Revoked),
            "expired" => Ok(Self::Expired),
            "password_failed" => Ok(Self::PasswordFailed),
            _ => Err(format!("unknown share activity action: {}", s)),
        }
    }
}

/// Activity log entry for a share.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ShareActivity {
    pub id: Uuid,
    pub share_id: ShareId,
    pub actor_id: Option<UserId>,
    pub actor_ip: Option<String>,
    pub action: ShareActivityAction,
    pub details: Option<String>,
    pub timestamp: DateTime<Utc>,
}

impl ShareActivity {
    pub fn new(share_id: ShareId, action: ShareActivityAction) -> Self {
        Self {
            id: Uuid::now_v7(),
            share_id,
            actor_id: None,
            actor_ip: None,
            action,
            details: None,
            timestamp: Utc::now(),
        }
    }

    pub fn with_actor(mut self, actor_id: UserId) -> Self {
        self.actor_id = Some(actor_id);
        self
    }

    pub fn with_ip(mut self, ip: &str) -> Self {
        self.actor_ip = Some(ip.to_string());
        self
    }

    pub fn with_details(mut self, details: &str) -> Self {
        self.details = Some(details.to_string());
        self
    }
}

/// Types of share notifications.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum ShareNotificationType {
    NewShare,
    ShareUpdated,
    ShareRevoked,
    ShareExpiring,
    ShareAccessed,
}

impl fmt::Display for ShareNotificationType {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::NewShare => write!(f, "new_share"),
            Self::ShareUpdated => write!(f, "share_updated"),
            Self::ShareRevoked => write!(f, "share_revoked"),
            Self::ShareExpiring => write!(f, "share_expiring"),
            Self::ShareAccessed => write!(f, "share_accessed"),
        }
    }
}

impl std::str::FromStr for ShareNotificationType {
    type Err = String;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s.to_lowercase().as_str() {
            "new_share" => Ok(Self::NewShare),
            "share_updated" => Ok(Self::ShareUpdated),
            "share_revoked" => Ok(Self::ShareRevoked),
            "share_expiring" => Ok(Self::ShareExpiring),
            "share_accessed" => Ok(Self::ShareAccessed),
            _ => Err(format!("unknown share notification type: {}", s)),
        }
    }
}

/// A notification about a share.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ShareNotification {
    pub id: Uuid,
    pub user_id: UserId,
    pub share_id: ShareId,
    pub notification_type: ShareNotificationType,
    pub is_read: bool,
    pub created_at: DateTime<Utc>,
}

impl ShareNotification {
    pub fn new(
        user_id: UserId,
        share_id: ShareId,
        notification_type: ShareNotificationType,
    ) -> Self {
        Self {
            id: Uuid::now_v7(),
            user_id,
            share_id,
            notification_type,
            is_read: false,
            created_at: Utc::now(),
        }
    }
}

/// Generate a random share token using UUID.
pub fn generate_share_token() -> String {
    // Use UUIDv4 for random tokens - simple string representation
    Uuid::new_v4().simple().to_string()
}

/// Hash a share password.
pub fn hash_share_password(password: &str) -> String {
    // Use BLAKE3 for password hashing (in production, use Argon2)
    blake3::hash(password.as_bytes()).to_hex().to_string()
}

/// Verify a share password.
pub fn verify_share_password(password: &str, hash: &str) -> bool {
    let computed = hash_share_password(password);
    computed == hash
}