use anyhow::Result;
use async_recursion::async_recursion;
use collections::HashSet;
use futures::{stream::FuturesUnordered, StreamExt as _};
use gpui::{AppContext as _, AsyncWindowContext, Axis, Entity, Task, WeakEntity};
use project::{terminals::TerminalKind, Project};
use serde::{Deserialize, Serialize};
use std::path::{Path, PathBuf};
use ui::{App, Context, Pixels, Window};
use util::ResultExt as _;

use db::{define_connection, query, sqlez::statement::Statement, sqlez_macros::sql};
use workspace::{
    ItemHandle, ItemId, Member, Pane, PaneAxis, PaneGroup, SerializableItem as _, Workspace,
    WorkspaceDb, WorkspaceId,
};

use crate::{
    default_working_directory,
    terminal_panel::{new_terminal_pane, TerminalPanel},
    TerminalView,
};

pub(crate) fn serialize_pane_group(
    pane_group: &PaneGroup,
    active_pane: &Entity<Pane>,
    cx: &mut App,
) -> SerializedPaneGroup {
    build_serialized_pane_group(&pane_group.root, active_pane, cx)
}

fn build_serialized_pane_group(
    pane_group: &Member,
    active_pane: &Entity<Pane>,
    cx: &mut App,
) -> SerializedPaneGroup {
    match pane_group {
        Member::Axis(PaneAxis {
            axis,
            members,
            flexes,
            bounding_boxes: _,
        }) => SerializedPaneGroup::Group {
            axis: SerializedAxis(*axis),
            children: members
                .iter()
                .map(|member| build_serialized_pane_group(member, active_pane, cx))
                .collect::<Vec<_>>(),
            flexes: Some(flexes.lock().clone()),
        },
        Member::Pane(pane_handle) => {
            SerializedPaneGroup::Pane(serialize_pane(pane_handle, pane_handle == active_pane, cx))
        }
    }
}

fn serialize_pane(pane: &Entity<Pane>, active: bool, cx: &mut App) -> SerializedPane {
    let mut items_to_serialize = HashSet::default();
    let pane = pane.read(cx);
    let children = pane
        .items()
        .filter_map(|item| {
            let terminal_view = item.act_as::<TerminalView>(cx)?;
            if terminal_view.read(cx).terminal().read(cx).task().is_some() {
                None
            } else {
                let id = item.item_id().as_u64();
                items_to_serialize.insert(id);
                Some(id)
            }
        })
        .collect::<Vec<_>>();
    let active_item = pane
        .active_item()
        .map(|item| item.item_id().as_u64())
        .filter(|active_id| items_to_serialize.contains(active_id));

    SerializedPane {
        active,
        children,
        active_item,
    }
}

pub(crate) fn deserialize_terminal_panel(
    workspace: WeakEntity<Workspace>,
    project: Entity<Project>,
    database_id: WorkspaceId,
    serialized_panel: SerializedTerminalPanel,
    window: &mut Window,
    cx: &mut App,
) -> Task<anyhow::Result<Entity<TerminalPanel>>> {
    window.spawn(cx, move |mut cx| async move {
        let terminal_panel = workspace.update_in(&mut cx, |workspace, window, cx| {
            cx.new(|cx| {
                let mut panel = TerminalPanel::new(workspace, window, cx);
                panel.height = serialized_panel.height.map(|h| h.round());
                panel.width = serialized_panel.width.map(|w| w.round());
                panel
            })
        })?;
        match &serialized_panel.items {
            SerializedItems::NoSplits(item_ids) => {
                let items = deserialize_terminal_views(
                    database_id,
                    project,
                    workspace,
                    item_ids.as_slice(),
                    &mut cx,
                )
                .await;
                let active_item = serialized_panel.active_item_id;
                terminal_panel.update_in(&mut cx, |terminal_panel, window, cx| {
                    terminal_panel.active_pane.update(cx, |pane, cx| {
                        populate_pane_items(pane, items, active_item, window, cx);
                    });
                })?;
            }
            SerializedItems::WithSplits(serialized_pane_group) => {
                let center_pane = deserialize_pane_group(
                    workspace,
                    project,
                    terminal_panel.clone(),
                    database_id,
                    serialized_pane_group,
                    &mut cx,
                )
                .await;
                if let Some((center_group, active_pane)) = center_pane {
                    terminal_panel.update(&mut cx, |terminal_panel, _| {
                        terminal_panel.center = PaneGroup::with_root(center_group);
                        terminal_panel.active_pane =
                            active_pane.unwrap_or_else(|| terminal_panel.center.first_pane());
                    })?;
                }
            }
        }

        Ok(terminal_panel)
    })
}

fn populate_pane_items(
    pane: &mut Pane,
    items: Vec<Entity<TerminalView>>,
    active_item: Option<u64>,
    window: &mut Window,
    cx: &mut Context<Pane>,
) {
    let mut item_index = pane.items_len();
    let mut active_item_index = None;
    for item in items {
        if Some(item.item_id().as_u64()) == active_item {
            active_item_index = Some(item_index);
        }
        pane.add_item(Box::new(item), false, false, None, window, cx);
        item_index += 1;
    }
    if let Some(index) = active_item_index {
        pane.activate_item(index, false, false, window, cx);
    }
}

#[async_recursion(?Send)]
async fn deserialize_pane_group(
    workspace: WeakEntity<Workspace>,
    project: Entity<Project>,
    panel: Entity<TerminalPanel>,
    workspace_id: WorkspaceId,
    serialized: &SerializedPaneGroup,
    cx: &mut AsyncWindowContext,
) -> Option<(Member, Option<Entity<Pane>>)> {
    match serialized {
        SerializedPaneGroup::Group {
            axis,
            flexes,
            children,
        } => {
            let mut current_active_pane = None;
            let mut members = Vec::new();
            for child in children {
                if let Some((new_member, active_pane)) = deserialize_pane_group(
                    workspace.clone(),
                    project.clone(),
                    panel.clone(),
                    workspace_id,
                    child,
                    cx,
                )
                .await
                {
                    members.push(new_member);
                    current_active_pane = current_active_pane.or(active_pane);
                }
            }

            if members.is_empty() {
                return None;
            }

            if members.len() == 1 {
                return Some((members.remove(0), current_active_pane));
            }

            Some((
                Member::Axis(PaneAxis::load(axis.0, members, flexes.clone())),
                current_active_pane,
            ))
        }
        SerializedPaneGroup::Pane(serialized_pane) => {
            let active = serialized_pane.active;
            let new_items = deserialize_terminal_views(
                workspace_id,
                project.clone(),
                workspace.clone(),
                serialized_pane.children.as_slice(),
                cx,
            )
            .await;

            let pane = panel
                .update_in(cx, |terminal_panel, window, cx| {
                    new_terminal_pane(
                        workspace.clone(),
                        project.clone(),
                        terminal_panel.active_pane.read(cx).is_zoomed(),
                        window,
                        cx,
                    )
                })
                .log_err()?;
            let active_item = serialized_pane.active_item;

            let terminal = pane
                .update_in(cx, |pane, window, cx| {
                    populate_pane_items(pane, new_items, active_item, window, cx);
                    // Avoid blank panes in splits
                    if pane.items_len() == 0 {
                        let working_directory = workspace
                            .update(cx, |workspace, cx| default_working_directory(workspace, cx))
                            .ok()
                            .flatten();
                        let kind = TerminalKind::Shell(
                            working_directory.as_deref().map(Path::to_path_buf),
                        );
                        let window = window.window_handle();
                        let terminal = project
                            .update(cx, |project, cx| project.create_terminal(kind, window, cx));
                        Some(Some(terminal))
                    } else {
                        Some(None)
                    }
                })
                .ok()
                .flatten()?;
            if let Some(terminal) = terminal {
                let terminal = terminal.await.ok()?;
                pane.update_in(cx, |pane, window, cx| {
                    let terminal_view = Box::new(cx.new(|cx| {
                        TerminalView::new(
                            terminal,
                            workspace.clone(),
                            Some(workspace_id),
                            project.downgrade(),
                            window,
                            cx,
                        )
                    }));
                    pane.add_item(terminal_view, true, false, None, window, cx);
                })
                .ok()?;
            }
            Some((Member::Pane(pane.clone()), active.then_some(pane)))
        }
    }
}

async fn deserialize_terminal_views(
    workspace_id: WorkspaceId,
    project: Entity<Project>,
    workspace: WeakEntity<Workspace>,
    item_ids: &[u64],
    cx: &mut AsyncWindowContext,
) -> Vec<Entity<TerminalView>> {
    let mut items = Vec::with_capacity(item_ids.len());
    let mut deserialized_items = item_ids
        .iter()
        .map(|item_id| {
            cx.update(|window, cx| {
                TerminalView::deserialize(
                    project.clone(),
                    workspace.clone(),
                    workspace_id,
                    *item_id,
                    window,
                    cx,
                )
            })
            .unwrap_or_else(|e| Task::ready(Err(e.context("no window present"))))
        })
        .collect::<FuturesUnordered<_>>();
    while let Some(item) = deserialized_items.next().await {
        if let Some(item) = item.log_err() {
            items.push(item);
        }
    }
    items
}

#[derive(Debug, Serialize, Deserialize)]
pub(crate) struct SerializedTerminalPanel {
    pub items: SerializedItems,
    // A deprecated field, kept for backwards compatibility for the code before terminal splits were introduced.
    pub active_item_id: Option<u64>,
    pub width: Option<Pixels>,
    pub height: Option<Pixels>,
}

#[derive(Debug, Serialize, Deserialize)]
#[serde(untagged)]
pub(crate) enum SerializedItems {
    // The data stored before terminal splits were introduced.
    NoSplits(Vec<u64>),
    WithSplits(SerializedPaneGroup),
}

#[derive(Debug, Serialize, Deserialize)]
pub(crate) enum SerializedPaneGroup {
    Pane(SerializedPane),
    Group {
        axis: SerializedAxis,
        flexes: Option<Vec<f32>>,
        children: Vec<SerializedPaneGroup>,
    },
}

#[derive(Debug, Serialize, Deserialize)]
pub(crate) struct SerializedPane {
    pub active: bool,
    pub children: Vec<u64>,
    pub active_item: Option<u64>,
}

#[derive(Debug)]
pub(crate) struct SerializedAxis(pub Axis);

impl Serialize for SerializedAxis {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        match self.0 {
            Axis::Horizontal => serializer.serialize_str("horizontal"),
            Axis::Vertical => serializer.serialize_str("vertical"),
        }
    }
}

impl<'de> Deserialize<'de> for SerializedAxis {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        let s = String::deserialize(deserializer)?;
        match s.as_str() {
            "horizontal" => Ok(SerializedAxis(Axis::Horizontal)),
            "vertical" => Ok(SerializedAxis(Axis::Vertical)),
            invalid => Err(serde::de::Error::custom(format!(
                "Invalid axis value: '{invalid}'"
            ))),
        }
    }
}

define_connection! {
    pub static ref TERMINAL_DB: TerminalDb<WorkspaceDb> =
        &[sql!(
            CREATE TABLE terminals (
                workspace_id INTEGER,
                item_id INTEGER UNIQUE,
                working_directory BLOB,
                PRIMARY KEY(workspace_id, item_id),
                FOREIGN KEY(workspace_id) REFERENCES workspaces(workspace_id)
                ON DELETE CASCADE
            ) STRICT;
        ),
        // Remove the unique constraint on the item_id table
        // SQLite doesn't have a way of doing this automatically, so
        // we have to do this silly copying.
        sql!(
            CREATE TABLE terminals2 (
                workspace_id INTEGER,
                item_id INTEGER,
                working_directory BLOB,
                PRIMARY KEY(workspace_id, item_id),
                FOREIGN KEY(workspace_id) REFERENCES workspaces(workspace_id)
                ON DELETE CASCADE
            ) STRICT;

            INSERT INTO terminals2 (workspace_id, item_id, working_directory)
            SELECT workspace_id, item_id, working_directory FROM terminals;

            DROP TABLE terminals;

            ALTER TABLE terminals2 RENAME TO terminals;
        )];
}

impl TerminalDb {
    query! {
       pub async fn update_workspace_id(
            new_id: WorkspaceId,
            old_id: WorkspaceId,
            item_id: ItemId
        ) -> Result<()> {
            UPDATE terminals
            SET workspace_id = ?
            WHERE workspace_id = ? AND item_id = ?
        }
    }

    query! {
        pub async fn save_working_directory(
            item_id: ItemId,
            workspace_id: WorkspaceId,
            working_directory: PathBuf
        ) -> Result<()> {
            INSERT OR REPLACE INTO terminals(item_id, workspace_id, working_directory)
            VALUES (?, ?, ?)
        }
    }

    query! {
        pub fn get_working_directory(item_id: ItemId, workspace_id: WorkspaceId) -> Result<Option<PathBuf>> {
            SELECT working_directory
            FROM terminals
            WHERE item_id = ? AND workspace_id = ?
        }
    }

    pub async fn delete_unloaded_items(
        &self,
        workspace: WorkspaceId,
        alive_items: Vec<ItemId>,
    ) -> Result<()> {
        let placeholders = alive_items
            .iter()
            .map(|_| "?")
            .collect::<Vec<&str>>()
            .join(", ");

        let query = format!(
            "DELETE FROM terminals WHERE workspace_id = ? AND item_id NOT IN ({placeholders})"
        );

        self.write(move |conn| {
            let mut statement = Statement::prepare(conn, query)?;
            let mut next_index = statement.bind(&workspace, 1)?;
            for id in alive_items {
                next_index = statement.bind(&id, next_index)?;
            }
            statement.exec()
        })
        .await
    }
}
