//! What a pane *is*, what it can be *looked at* through, and what its process
//! is *doing* — the three descriptions the renderer draws from.
//!
//! A pane is the durable unit of work in Lumbridge; a surface is a view over
//! that work. Keeping the two apart is a product boundary, not a rendering
//! convenience: switching a tab never launches a process, never moves the pane,
//! and never changes which agent owns the session. It changes what is drawn and
//! nothing else, which is why [`SurfaceTab`] is a plain enum with no handle to
//! anything and no way to reach a runtime.
//!
//! The other rule this file encodes is that an unsupported surface is shown as
//! unavailable rather than simulated. Every tab exists on every pane, and the
//! five a pane cannot serve say plainly why — "No isolated web engine is wired
//! yet", not an empty panel that reads as a bug, and never a plausible-looking
//! mock that a user would take for a working feature. Those sentences are the
//! product's honesty about how much of itself is built, so they are asserted
//! here rather than left to whoever last edited the renderer.
//!
//! [`LiveRuntimeStatus`] is the same idea applied to a process: four states, a
//! badge for the header and a detail line, and no attempt to summarise a fault
//! into something reassuring. None of it needs a renderer, so none of it lives
//! next to one.

use lumbridge_ui_fixture::{OutputSource, PaneStatus, SurfaceKind};

use crate::panel_registry::PanelId;

/// The surfaces a pane can be viewed through.
///
/// A pane is the durable unit of work and its surface is a view over that work.
/// Switching one never launches a process, moves the pane, or changes which
/// agent owns the session — it only changes what is drawn.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub(crate) enum SurfaceTab {
    Terminal,
    Browser,
    Tools,
    Context,
    Goal,
    Review,
}

impl SurfaceTab {
    pub(crate) const ALL: [Self; 6] = [
        Self::Terminal,
        Self::Browser,
        Self::Tools,
        Self::Context,
        Self::Goal,
        Self::Review,
    ];

    pub(crate) const fn label(self) -> &'static str {
        match self {
            Self::Terminal => "TERMINAL",
            Self::Browser => "BROWSER",
            Self::Tools => "TOOLS",
            Self::Context => "CONTEXT",
            Self::Goal => "GOAL",
            Self::Review => "REVIEW",
        }
    }

    pub(crate) const fn ordinal(self) -> u64 {
        match self {
            Self::Terminal => 0,
            Self::Browser => 1,
            Self::Tools => 2,
            Self::Context => 3,
            Self::Goal => 4,
            Self::Review => 5,
        }
    }

    /// The one surface a pane of this kind actually provides.
    pub(crate) const fn native_for(kind: SurfaceKind) -> Self {
        match kind {
            SurfaceKind::Terminal => Self::Terminal,
            SurfaceKind::Browser => Self::Browser,
            SurfaceKind::Markdown => Self::Context,
            SurfaceKind::Review => Self::Review,
        }
    }

    /// Why this pane cannot show this surface. Stated plainly, because the
    /// product boundary says an unsupported surface is shown as unavailable
    /// rather than simulated.
    pub(crate) const fn unavailable_reason(self) -> &'static str {
        match self {
            Self::Terminal => "Only a terminal pane owns a live shell.",
            Self::Browser => "No isolated web engine is wired yet.",
            Self::Tools => "Tool calls arrive with the ACP client.",
            Self::Context => "Context projection is not built yet.",
            Self::Goal => "Goal tracking is not built yet.",
            Self::Review => "Review is not wired to Git yet.",
        }
    }
}

#[derive(Clone)]
pub(crate) struct PanelView {
    pub(crate) id: PanelId,
    pub(crate) kind: SurfaceKind,
    pub(crate) title: String,
    pub(crate) badge: String,
    pub(crate) target: String,
    pub(crate) status: PaneStatus,
    pub(crate) lines: Vec<String>,
    pub(crate) output_source: OutputSource,
}

impl PanelView {
    pub(crate) const fn needs_input(&self) -> bool {
        matches!(self.status, PaneStatus::NeedsInput)
    }
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub(crate) enum LiveRuntimeStatus {
    Starting,
    Running {
        session_id: u64,
        process_id: Option<u32>,
    },
    Exited(String),
    Fault(String),
}

impl LiveRuntimeStatus {
    pub(crate) fn badge(&self) -> &'static str {
        match self {
            Self::Starting => "PTY STARTING",
            Self::Running { .. } => "LIVE PTY",
            Self::Exited(_) => "PTY EXITED",
            Self::Fault(_) => "PTY FAULT",
        }
    }

    pub(crate) fn detail(&self) -> String {
        match self {
            Self::Starting => "local · runtime actor starting".to_owned(),
            Self::Running {
                session_id,
                process_id,
            } => match process_id {
                Some(process_id) => {
                    format!("local · runtime session {session_id} · pid {process_id}")
                }
                None => format!("local · runtime session {session_id}"),
            },
            Self::Exited(status) => format!("local · {status}"),
            Self::Fault(message) => format!("local · {message}"),
        }
    }

    pub(crate) const fn is_terminal(&self) -> bool {
        matches!(self, Self::Exited(_) | Self::Fault(_))
    }
}

#[cfg(test)]
mod tests {
    use super::{LiveRuntimeStatus, SurfaceTab};
    use lumbridge_ui_fixture::SurfaceKind;

    #[test]
    fn every_pane_kind_opens_on_the_surface_it_actually_provides() {
        // The failure this prevents is a pane whose default tab is one it
        // cannot serve: the workspace would open on an "unavailable" panel and
        // read as broken before the user has touched anything.
        for kind in [
            SurfaceKind::Terminal,
            SurfaceKind::Browser,
            SurfaceKind::Markdown,
            SurfaceKind::Review,
        ] {
            let native = SurfaceTab::native_for(kind);
            assert!(
                SurfaceTab::ALL.contains(&native),
                "{kind:?} opens on a tab the tab bar does not draw"
            );
        }

        // Markdown is the one that is not its own name: there is no MARKDOWN
        // tab, and a document pane is read through CONTEXT.
        assert_eq!(
            SurfaceTab::native_for(SurfaceKind::Markdown),
            SurfaceTab::Context
        );
        assert_eq!(
            SurfaceTab::native_for(SurfaceKind::Terminal),
            SurfaceTab::Terminal
        );
        assert_eq!(
            SurfaceTab::native_for(SurfaceKind::Browser),
            SurfaceTab::Browser
        );
        assert_eq!(
            SurfaceTab::native_for(SurfaceKind::Review),
            SurfaceTab::Review
        );
    }

    #[test]
    fn the_tab_bar_lists_every_surface_exactly_once_and_in_a_stable_order() {
        // ordinal() is mixed into the element ID a pane's tabs are built with,
        // so a duplicate would collide two tabs into one element, and a gap
        // would only show up as a tab that cannot be clicked.
        for (index, tab) in SurfaceTab::ALL.into_iter().enumerate() {
            assert_eq!(
                u64::try_from(index).expect("six tabs fit in a u64"),
                tab.ordinal(),
                "{tab:?} is at position {index} but reports ordinal {}",
                tab.ordinal()
            );
        }
    }

    #[test]
    fn no_surface_is_unavailable_without_saying_why() {
        // An unsupported surface is shown as unavailable rather than simulated,
        // and "unavailable" with no sentence after it is indistinguishable from
        // a panel that failed to render.
        for tab in SurfaceTab::ALL {
            let reason = tab.unavailable_reason();
            assert!(
                !reason.is_empty() && reason.ends_with('.'),
                "{tab:?} owes the user a complete sentence, not {reason:?}"
            );
            assert!(
                !tab.label().is_empty(),
                "{tab:?} has no label for the tab bar"
            );
        }

        // Distinct sentences, not one generic line repeated six times: the
        // reason a browser pane is empty and the reason review is empty are
        // different facts about how much of the product exists.
        let mut reasons = SurfaceTab::ALL.map(SurfaceTab::unavailable_reason).to_vec();
        reasons.sort_unstable();
        let before = reasons.len();
        reasons.dedup();
        assert_eq!(before, reasons.len(), "two surfaces share an excuse");
    }

    #[test]
    fn a_running_pty_names_its_pid_when_the_runtime_reported_one() {
        // The pid is what a user needs to go and look at the process from
        // outside Lumbridge, and it is genuinely absent on a session the actor
        // has accepted but not yet spawned. Printing "pid None" or a zero would
        // send someone hunting for a process that does not exist.
        assert_eq!(
            LiveRuntimeStatus::Running {
                session_id: 7,
                process_id: Some(4321),
            }
            .detail(),
            "local · runtime session 7 · pid 4321"
        );
        assert_eq!(
            LiveRuntimeStatus::Running {
                session_id: 7,
                process_id: None,
            }
            .detail(),
            "local · runtime session 7"
        );
    }

    #[test]
    fn every_status_reports_where_it_is_running_and_a_fault_keeps_its_message() {
        assert_eq!(
            LiveRuntimeStatus::Starting.detail(),
            "local · runtime actor starting"
        );
        // The message is carried through rather than summarised: "PTY FAULT" is
        // the badge, and the badge alone never tells anyone what to fix.
        assert_eq!(
            LiveRuntimeStatus::Fault("spawn failed: no such file".to_owned()).detail(),
            "local · spawn failed: no such file"
        );
        assert_eq!(
            LiveRuntimeStatus::Exited("exited with status 130".to_owned()).detail(),
            "local · exited with status 130"
        );
    }

    #[test]
    fn only_the_states_a_process_cannot_leave_are_terminal() {
        // is_terminal decides whether the event drain keeps polling a pane.
        // Calling Starting terminal would abandon a pane before it ever ran;
        // calling Exited non-terminal would poll a dead actor forever.
        assert!(LiveRuntimeStatus::Exited(String::new()).is_terminal());
        assert!(LiveRuntimeStatus::Fault(String::new()).is_terminal());
        assert!(!LiveRuntimeStatus::Starting.is_terminal());
        assert!(
            !LiveRuntimeStatus::Running {
                session_id: 1,
                process_id: None,
            }
            .is_terminal()
        );
    }

    #[test]
    fn each_status_has_its_own_badge() {
        let badges = [
            LiveRuntimeStatus::Starting.badge(),
            LiveRuntimeStatus::Running {
                session_id: 1,
                process_id: None,
            }
            .badge(),
            LiveRuntimeStatus::Exited(String::new()).badge(),
            LiveRuntimeStatus::Fault(String::new()).badge(),
        ];
        let mut sorted = badges.to_vec();
        sorted.sort_unstable();
        sorted.dedup();
        assert_eq!(
            sorted.len(),
            badges.len(),
            "two runtime states would look identical in the pane header"
        );
    }
}