//! Storage-owned TOTP catalog and detail state for native mobile frontends.

use std::{collections::BTreeSet, error::Error, fmt};

use crate::{
    crypto::{KeyStore, SecretProvider},
    otp::{OtpError, OtpKind, OtpService},
    repository::{EntryPath, Repository, RepositoryError, SecretBytes},
};

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum MobileWatchSnapshotState {
    Unavailable,
    Pending,
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct MobileWatchSnapshotStatus {
    state: MobileWatchSnapshotState,
    detail: String,
}

impl MobileWatchSnapshotStatus {
    pub fn state(&self) -> MobileWatchSnapshotState {
        self.state
    }

    pub fn detail(&self) -> &str {
        &self.detail
    }
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct MobileTotpRow {
    path: String,
    issuer: Option<String>,
    account: String,
    title: String,
    detail: String,
    shared_with_watch: bool,
}

impl MobileTotpRow {
    pub fn path(&self) -> &str {
        &self.path
    }

    pub fn issuer(&self) -> Option<&str> {
        self.issuer.as_deref()
    }

    pub fn account(&self) -> &str {
        &self.account
    }

    pub fn title(&self) -> &str {
        &self.title
    }

    pub fn detail(&self) -> &str {
        &self.detail
    }

    pub fn shared_with_watch(&self) -> bool {
        self.shared_with_watch
    }
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct MobileTotpPage {
    rows: Vec<MobileTotpRow>,
    unavailable_entries: u32,
    watch: MobileWatchSnapshotStatus,
}

impl MobileTotpPage {
    pub fn rows(&self) -> &[MobileTotpRow] {
        &self.rows
    }

    pub fn unavailable_entries(&self) -> u32 {
        self.unavailable_entries
    }

    pub fn watch(&self) -> &MobileWatchSnapshotStatus {
        &self.watch
    }
}

pub struct MobileTotpDetail {
    path: String,
    issuer: Option<String>,
    account: String,
    code: SecretBytes,
    valid_until: u64,
    period: u64,
    shared_with_watch: bool,
    watch: MobileWatchSnapshotStatus,
}

impl MobileTotpDetail {
    pub fn path(&self) -> &str {
        &self.path
    }

    pub fn issuer(&self) -> Option<&str> {
        self.issuer.as_deref()
    }

    pub fn account(&self) -> &str {
        &self.account
    }

    pub fn code(&self) -> &SecretBytes {
        &self.code
    }

    pub fn valid_until(&self) -> u64 {
        self.valid_until
    }

    pub fn period(&self) -> u64 {
        self.period
    }

    pub fn shared_with_watch(&self) -> bool {
        self.shared_with_watch
    }

    pub fn watch(&self) -> &MobileWatchSnapshotStatus {
        &self.watch
    }
}

impl fmt::Debug for MobileTotpDetail {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter
            .debug_struct("MobileTotpDetail")
            .field("path", &self.path)
            .field("issuer", &self.issuer)
            .field("account", &self.account)
            .field("code", &"[REDACTED]")
            .field("valid_until", &self.valid_until)
            .field("period", &self.period)
            .field("shared_with_watch", &self.shared_with_watch)
            .field("watch", &self.watch)
            .finish()
    }
}

pub struct MobileTotpService<'a> {
    repository: &'a Repository,
    keys: &'a KeyStore,
}

impl<'a> MobileTotpService<'a> {
    pub fn new(repository: &'a Repository, keys: &'a KeyStore) -> Self {
        Self { repository, keys }
    }

    pub fn page(
        &self,
        shared: &BTreeSet<EntryPath>,
        provider: &mut impl SecretProvider,
    ) -> Result<MobileTotpPage, MobileTotpError> {
        let snapshot = self.repository.snapshot()?;
        let mut rows = Vec::new();
        let mut unavailable_entries = 0_u32;
        for entry in snapshot.entries() {
            match OtpService::new(self.repository, self.keys)
                .uri(&entry.path().to_string(), provider)
            {
                Ok(uri) if uri.kind() == OtpKind::Totp => rows.push(row(
                    entry.path(),
                    uri.issuer(),
                    uri.account(),
                    shared.contains(entry.path()),
                )),
                Ok(_) | Err(OtpError::MissingUri { .. } | OtpError::AmbiguousUri { .. }) => {}
                Err(OtpError::Crypto(_)) => {
                    unavailable_entries = unavailable_entries.saturating_add(1);
                }
                Err(OtpError::Repository(error)) => return Err(error.into()),
                Err(_) => {}
            }
        }
        rows.sort_by(|left, right| {
            left.title
                .to_lowercase()
                .cmp(&right.title.to_lowercase())
                .then_with(|| {
                    left.account
                        .to_lowercase()
                        .cmp(&right.account.to_lowercase())
                })
                .then_with(|| left.path.cmp(&right.path))
        });
        let selected = rows.iter().filter(|row| row.shared_with_watch).count();
        Ok(MobileTotpPage {
            rows,
            unavailable_entries,
            watch: snapshot_status(selected),
        })
    }

    pub fn detail(
        &self,
        entry: &str,
        unix_seconds: u64,
        shared: &BTreeSet<EntryPath>,
        provider: &mut impl SecretProvider,
    ) -> Result<MobileTotpDetail, MobileTotpError> {
        let path = EntryPath::parse(entry)?;
        let uri = OtpService::new(self.repository, self.keys).uri(entry, provider)?;
        if uri.kind() != OtpKind::Totp {
            return Err(OtpError::NotTotp.into());
        }
        let period = uri.period().ok_or(OtpError::NotTotp)?;
        let valid_until = (unix_seconds / period)
            .checked_add(1)
            .and_then(|counter| counter.checked_mul(period))
            .ok_or(OtpError::CounterOverflow)?;
        let shared_with_watch = shared.contains(&path);
        Ok(MobileTotpDetail {
            path: path.to_string(),
            issuer: uri.issuer().map(str::to_owned),
            account: uri.account().to_owned(),
            code: uri.code_at(unix_seconds)?,
            valid_until,
            period,
            shared_with_watch,
            watch: snapshot_status(shared.len()),
        })
    }
}

fn row(
    path: &EntryPath,
    issuer: Option<&str>,
    account: &str,
    shared_with_watch: bool,
) -> MobileTotpRow {
    MobileTotpRow {
        path: path.to_string(),
        issuer: issuer.map(str::to_owned),
        account: account.to_owned(),
        title: issuer.unwrap_or(account).to_owned(),
        detail: issuer.map_or_else(|| path.to_string(), |_| account.to_owned()),
        shared_with_watch,
    }
}

fn snapshot_status(selected: usize) -> MobileWatchSnapshotStatus {
    if selected == 0 {
        MobileWatchSnapshotStatus {
            state: MobileWatchSnapshotState::Unavailable,
            detail: "No TOTP codes are selected for Apple Watch.".to_owned(),
        }
    } else {
        MobileWatchSnapshotStatus {
            state: MobileWatchSnapshotState::Pending,
            detail: format!(
                "{selected} selected TOTP {} pending Apple Watch synchronization.",
                if selected == 1 {
                    "code is"
                } else {
                    "codes are"
                }
            ),
        }
    }
}

#[derive(Debug)]
pub enum MobileTotpError {
    Repository(RepositoryError),
    Otp(OtpError),
}

impl fmt::Display for MobileTotpError {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Repository(error) => error.fmt(formatter),
            Self::Otp(error) => error.fmt(formatter),
        }
    }
}

impl Error for MobileTotpError {}

impl From<RepositoryError> for MobileTotpError {
    fn from(error: RepositoryError) -> Self {
        Self::Repository(error)
    }
}

impl From<OtpError> for MobileTotpError {
    fn from(error: OtpError) -> Self {
        Self::Otp(error)
    }
}