mod appearance_settings_controls;

use std::any::TypeId;
use std::collections::VecDeque;
use std::ops::{Not, Range};

use anyhow::Context as _;
use command_palette_hooks::CommandPaletteFilter;
use editor::EditorSettingsControls;
use feature_flags::{FeatureFlag, FeatureFlagViewExt};
use gpui::{App, Entity, EventEmitter, FocusHandle, Focusable, ReadGlobal, actions};
use settings::{
    NumType, SettingsStore, SettingsUiEntry, SettingsUiItem, SettingsUiItemDynamic,
    SettingsUiItemGroup, SettingsUiItemSingle, SettingsValue,
};
use smallvec::SmallVec;
use ui::{NumericStepper, SwitchField, ToggleButtonGroup, ToggleButtonSimple, prelude::*};
use workspace::{
    Workspace,
    item::{Item, ItemEvent},
    with_active_or_new_workspace,
};

use crate::appearance_settings_controls::AppearanceSettingsControls;

pub struct SettingsUiFeatureFlag;

impl FeatureFlag for SettingsUiFeatureFlag {
    const NAME: &'static str = "settings-ui";
}

actions!(
    zed,
    [
        /// Opens the settings editor.
        OpenSettingsEditor
    ]
);

pub fn init(cx: &mut App) {
    cx.on_action(|_: &OpenSettingsEditor, cx| {
        with_active_or_new_workspace(cx, move |workspace, window, cx| {
            let existing = workspace
                .active_pane()
                .read(cx)
                .items()
                .find_map(|item| item.downcast::<SettingsPage>());

            if let Some(existing) = existing {
                workspace.activate_item(&existing, true, true, window, cx);
            } else {
                let settings_page = SettingsPage::new(workspace, cx);
                workspace.add_item_to_active_pane(Box::new(settings_page), None, true, window, cx)
            }
        });
    });

    cx.observe_new(|_workspace: &mut Workspace, window, cx| {
        let Some(window) = window else {
            return;
        };

        let settings_ui_actions = [TypeId::of::<OpenSettingsEditor>()];

        CommandPaletteFilter::update_global(cx, |filter, _cx| {
            filter.hide_action_types(&settings_ui_actions);
        });

        cx.observe_flag::<SettingsUiFeatureFlag, _>(
            window,
            move |is_enabled, _workspace, _, cx| {
                if is_enabled {
                    CommandPaletteFilter::update_global(cx, |filter, _cx| {
                        filter.show_action_types(settings_ui_actions.iter());
                    });
                } else {
                    CommandPaletteFilter::update_global(cx, |filter, _cx| {
                        filter.hide_action_types(&settings_ui_actions);
                    });
                }
            },
        )
        .detach();
    })
    .detach();
}

pub struct SettingsPage {
    focus_handle: FocusHandle,
    settings_tree: SettingsUiTree,
}

impl SettingsPage {
    pub fn new(_workspace: &Workspace, cx: &mut Context<Workspace>) -> Entity<Self> {
        cx.new(|cx| Self {
            focus_handle: cx.focus_handle(),
            settings_tree: SettingsUiTree::new(cx),
        })
    }
}

impl EventEmitter<ItemEvent> for SettingsPage {}

impl Focusable for SettingsPage {
    fn focus_handle(&self, _cx: &App) -> FocusHandle {
        self.focus_handle.clone()
    }
}

impl Item for SettingsPage {
    type Event = ItemEvent;

    fn tab_icon(&self, _window: &Window, _cx: &App) -> Option<Icon> {
        Some(Icon::new(IconName::Settings))
    }

    fn tab_content_text(&self, _detail: usize, _cx: &App) -> SharedString {
        "Settings".into()
    }

    fn show_toolbar(&self) -> bool {
        false
    }

    fn to_item_events(event: &Self::Event, mut f: impl FnMut(ItemEvent)) {
        f(*event)
    }
}

// We want to iterate over the side bar with root groups
// - this is a loop over top level groups, and if any are expanded, recursively displaying their items
// - Should be able to get all items from a group (flatten a group)
// - Should be able to toggle/untoggle groups in UI (at least in sidebar)
// - Search should be available
//  - there should be an index of text -> item mappings, for using fuzzy::match
//   - Do we want to show the parent groups when a item is matched?

struct UiEntry {
    title: &'static str,
    path: Option<&'static str>,
    _depth: usize,
    // a
    //  b     < a descendant range < a total descendant range
    //    f   |                    |
    //    g   |                    |
    //  c     <                    |
    //    d                        |
    //    e                        <
    descendant_range: Range<usize>,
    total_descendant_range: Range<usize>,
    next_sibling: Option<usize>,
    // expanded: bool,
    render: Option<SettingsUiItemSingle>,
    select_descendant: Option<fn(&serde_json::Value, &mut App) -> usize>,
}

impl UiEntry {
    fn first_descendant_index(&self) -> Option<usize> {
        return self
            .descendant_range
            .is_empty()
            .not()
            .then_some(self.descendant_range.start);
    }

    fn nth_descendant_index(&self, tree: &[UiEntry], n: usize) -> Option<usize> {
        let first_descendant_index = self.first_descendant_index()?;
        let mut current_index = 0;
        let mut current_descendant_index = Some(first_descendant_index);
        while let Some(descendant_index) = current_descendant_index
            && current_index < n
        {
            current_index += 1;
            current_descendant_index = tree[descendant_index].next_sibling;
        }
        current_descendant_index
    }
}

struct SettingsUiTree {
    root_entry_indices: Vec<usize>,
    entries: Vec<UiEntry>,
    active_entry_index: usize,
}

fn build_tree_item(
    tree: &mut Vec<UiEntry>,
    entry: SettingsUiEntry,
    depth: usize,
    prev_index: Option<usize>,
) {
    let index = tree.len();
    tree.push(UiEntry {
        title: entry.title,
        path: entry.path,
        _depth: depth,
        descendant_range: index + 1..index + 1,
        total_descendant_range: index + 1..index + 1,
        render: None,
        next_sibling: None,
        select_descendant: None,
    });
    if let Some(prev_index) = prev_index {
        tree[prev_index].next_sibling = Some(index);
    }
    match entry.item {
        SettingsUiItem::Group(SettingsUiItemGroup { items: group_items }) => {
            for group_item in group_items {
                let prev_index = tree[index]
                    .descendant_range
                    .is_empty()
                    .not()
                    .then_some(tree[index].descendant_range.end - 1);
                tree[index].descendant_range.end = tree.len() + 1;
                build_tree_item(tree, group_item, depth + 1, prev_index);
                tree[index].total_descendant_range.end = tree.len();
            }
        }
        SettingsUiItem::Single(item) => {
            tree[index].render = Some(item);
        }
        SettingsUiItem::Dynamic(SettingsUiItemDynamic {
            options,
            determine_option,
        }) => {
            tree[index].select_descendant = Some(determine_option);
            for option in options {
                let prev_index = tree[index]
                    .descendant_range
                    .is_empty()
                    .not()
                    .then_some(tree[index].descendant_range.end - 1);
                tree[index].descendant_range.end = tree.len() + 1;
                build_tree_item(tree, option, depth + 1, prev_index);
                tree[index].total_descendant_range.end = tree.len();
            }
        }
        SettingsUiItem::None => {
            return;
        }
    }
}

impl SettingsUiTree {
    fn new(cx: &App) -> Self {
        let settings_store = SettingsStore::global(cx);
        let mut tree = vec![];
        let mut root_entry_indices = vec![];
        for item in settings_store.settings_ui_items() {
            if matches!(item.item, SettingsUiItem::None)
            // todo(settings_ui): How to handle top level single items? BaseKeymap is in this category. Probably need a way to
            // link them to other groups
            || matches!(item.item, SettingsUiItem::Single(_))
            {
                continue;
            }

            let prev_root_entry_index = root_entry_indices.last().copied();
            root_entry_indices.push(tree.len());
            build_tree_item(&mut tree, item, 0, prev_root_entry_index);
        }

        root_entry_indices.sort_by_key(|i| tree[*i].title);

        let active_entry_index = root_entry_indices[0];
        Self {
            entries: tree,
            root_entry_indices,
            active_entry_index,
        }
    }
}

fn render_nav(tree: &SettingsUiTree, _window: &mut Window, cx: &mut Context<SettingsPage>) -> Div {
    let mut nav = v_flex().p_4().gap_2();
    for &index in &tree.root_entry_indices {
        nav = nav.child(
            div()
                .id(index)
                .on_click(cx.listener(move |settings, _, _, _| {
                    settings.settings_tree.active_entry_index = index;
                }))
                .child(
                    Label::new(SharedString::new_static(tree.entries[index].title))
                        .size(LabelSize::Large)
                        .when(tree.active_entry_index == index, |this| {
                            this.color(Color::Selected)
                        }),
                ),
        );
    }
    nav
}

fn render_content(
    tree: &SettingsUiTree,
    window: &mut Window,
    cx: &mut Context<SettingsPage>,
) -> impl IntoElement {
    let Some(active_entry) = tree.entries.get(tree.active_entry_index) else {
        return div()
            .size_full()
            .child(Label::new(SharedString::new_static("No settings found")).color(Color::Error));
    };
    let mut content = v_flex().size_full().gap_4().overflow_hidden();

    let mut path = smallvec::smallvec![];
    if let Some(active_entry_path) = active_entry.path {
        path.push(active_entry_path);
    }
    let mut entry_index_queue = VecDeque::new();

    if let Some(child_index) = active_entry.first_descendant_index() {
        entry_index_queue.push_back(child_index);
        let mut index = child_index;
        while let Some(next_sibling_index) = tree.entries[index].next_sibling {
            entry_index_queue.push_back(next_sibling_index);
            index = next_sibling_index;
        }
    };

    while let Some(index) = entry_index_queue.pop_front() {
        // todo(settings_ui): subgroups?
        let child = &tree.entries[index];
        let mut pushed_path = false;
        if let Some(child_path) = child.path {
            path.push(child_path);
            pushed_path = true;
        }
        let settings_value = settings_value_from_settings_and_path(
            path.clone(),
            child.title,
            // PERF: how to structure this better? There feels like there's a way to avoid the clone
            // and every value lookup
            SettingsStore::global(cx).raw_user_settings(),
            SettingsStore::global(cx).raw_default_settings(),
        );
        if let Some(select_descendant) = child.select_descendant {
            let selected_descendant = select_descendant(settings_value.read(), cx);
            if let Some(descendant_index) =
                child.nth_descendant_index(&tree.entries, selected_descendant)
            {
                entry_index_queue.push_front(descendant_index);
            }
        }
        if pushed_path {
            path.pop();
        }
        let Some(child_render) = child.render.as_ref() else {
            continue;
        };
        content = content.child(
            div()
                .child(Label::new(SharedString::new_static(child.title)).size(LabelSize::Large))
                .child(render_item_single(settings_value, child_render, window, cx)),
        );
    }

    return content;
}

impl Render for SettingsPage {
    fn render(&mut self, window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
        div()
            .grid()
            .grid_cols(16)
            .p_4()
            .bg(cx.theme().colors().editor_background)
            .size_full()
            .child(
                div()
                    .col_span(2)
                    .h_full()
                    .child(render_nav(&self.settings_tree, window, cx)),
            )
            .child(div().col_span(4).h_full().child(render_content(
                &self.settings_tree,
                window,
                cx,
            )))
    }
}

// todo(settings_ui): remove, only here as inspiration
#[allow(dead_code)]
fn render_old_appearance_settings(cx: &mut App) -> impl IntoElement {
    v_flex()
        .p_4()
        .size_full()
        .gap_4()
        .child(Label::new("Settings").size(LabelSize::Large))
        .child(
            v_flex().gap_1().child(Label::new("Appearance")).child(
                v_flex()
                    .elevation_2(cx)
                    .child(AppearanceSettingsControls::new()),
            ),
        )
        .child(
            v_flex().gap_1().child(Label::new("Editor")).child(
                v_flex()
                    .elevation_2(cx)
                    .child(EditorSettingsControls::new()),
            ),
        )
}

fn element_id_from_path(path: &[&'static str]) -> ElementId {
    if path.len() == 0 {
        panic!("Path length must not be zero");
    } else if path.len() == 1 {
        ElementId::Name(SharedString::new_static(path[0]))
    } else {
        ElementId::from((
            ElementId::from(SharedString::new_static(path[path.len() - 2])),
            SharedString::new_static(path[path.len() - 1]),
        ))
    }
}

fn render_item_single(
    settings_value: SettingsValue<serde_json::Value>,
    item: &SettingsUiItemSingle,
    window: &mut Window,
    cx: &mut App,
) -> AnyElement {
    match item {
        SettingsUiItemSingle::Custom(_) => div()
            .child(format!("Item: {}", settings_value.path.join(".")))
            .into_any_element(),
        SettingsUiItemSingle::SwitchField => {
            render_any_item(settings_value, render_switch_field, window, cx)
        }
        SettingsUiItemSingle::NumericStepper(num_type) => {
            render_any_numeric_stepper(settings_value, *num_type, window, cx)
        }
        SettingsUiItemSingle::ToggleGroup {
            variants: values,
            labels: titles,
        } => render_toggle_button_group(settings_value, values, titles, window, cx),
        SettingsUiItemSingle::DropDown { .. } => {
            unimplemented!("This")
        }
    }
}

fn read_settings_value_from_path<'a>(
    settings_contents: &'a serde_json::Value,
    path: &[&'static str],
) -> Option<&'a serde_json::Value> {
    // todo(settings_ui) make non recursive, and move to `settings` alongside SettingsValue, and add method to SettingsValue to get nested
    let Some((key, remaining)) = path.split_first() else {
        return Some(settings_contents);
    };
    let Some(value) = settings_contents.get(key) else {
        return None;
    };

    read_settings_value_from_path(value, remaining)
}

fn downcast_any_item<T: serde::de::DeserializeOwned>(
    settings_value: SettingsValue<serde_json::Value>,
) -> SettingsValue<T> {
    let value = settings_value
        .value
        .map(|value| serde_json::from_value::<T>(value).expect("value is not a T"));
    // todo(settings_ui) Create test that constructs UI tree, and asserts that all elements have default values
    let default_value = serde_json::from_value::<T>(settings_value.default_value)
        .with_context(|| format!("path: {:?}", settings_value.path.join(".")))
        .expect("default value is not an Option<T>");
    let deserialized_setting_value = SettingsValue {
        title: settings_value.title,
        path: settings_value.path,
        value,
        default_value,
    };
    deserialized_setting_value
}

fn render_any_item<T: serde::de::DeserializeOwned>(
    settings_value: SettingsValue<serde_json::Value>,
    render_fn: impl Fn(SettingsValue<T>, &mut Window, &mut App) -> AnyElement + 'static,
    window: &mut Window,
    cx: &mut App,
) -> AnyElement {
    let deserialized_setting_value = downcast_any_item(settings_value);
    render_fn(deserialized_setting_value, window, cx)
}

fn render_any_numeric_stepper(
    settings_value: SettingsValue<serde_json::Value>,
    num_type: NumType,
    window: &mut Window,
    cx: &mut App,
) -> AnyElement {
    match num_type {
        NumType::U64 => render_numeric_stepper::<u64>(
            downcast_any_item(settings_value),
            u64::saturating_sub,
            u64::saturating_add,
            |n| {
                serde_json::Number::try_from(n)
                    .context("Failed to convert u64 to serde_json::Number")
            },
            window,
            cx,
        ),
        NumType::U32 => render_numeric_stepper::<u32>(
            downcast_any_item(settings_value),
            u32::saturating_sub,
            u32::saturating_add,
            |n| {
                serde_json::Number::try_from(n)
                    .context("Failed to convert u32 to serde_json::Number")
            },
            window,
            cx,
        ),
        NumType::F32 => render_numeric_stepper::<f32>(
            downcast_any_item(settings_value),
            |a, b| a - b,
            |a, b| a + b,
            |n| {
                serde_json::Number::from_f64(n as f64)
                    .context("Failed to convert f32 to serde_json::Number")
            },
            window,
            cx,
        ),
    }
}

fn render_numeric_stepper<
    T: serde::de::DeserializeOwned + std::fmt::Display + Copy + From<u8> + 'static,
>(
    value: SettingsValue<T>,
    saturating_sub: fn(T, T) -> T,
    saturating_add: fn(T, T) -> T,
    to_serde_number: fn(T) -> anyhow::Result<serde_json::Number>,
    _window: &mut Window,
    _cx: &mut App,
) -> AnyElement {
    let id = element_id_from_path(&value.path);
    let path = value.path.clone();
    let num = *value.read();

    NumericStepper::new(
        id,
        num.to_string(),
        {
            let path = value.path.clone();
            move |_, _, cx| {
                let Some(number) = to_serde_number(saturating_sub(num, 1.into())).ok() else {
                    return;
                };
                let new_value = serde_json::Value::Number(number);
                SettingsValue::write_value(&path, new_value, cx);
            }
        },
        move |_, _, cx| {
            let Some(number) = to_serde_number(saturating_add(num, 1.into())).ok() else {
                return;
            };

            let new_value = serde_json::Value::Number(number);

            SettingsValue::write_value(&path, new_value, cx);
        },
    )
    .style(ui::NumericStepperStyle::Outlined)
    .into_any_element()
}

fn render_switch_field(
    value: SettingsValue<bool>,
    _window: &mut Window,
    _cx: &mut App,
) -> AnyElement {
    let id = element_id_from_path(&value.path);
    let path = value.path.clone();
    SwitchField::new(
        id,
        SharedString::new_static(value.title),
        None,
        match value.read() {
            true => ToggleState::Selected,
            false => ToggleState::Unselected,
        },
        move |toggle_state, _, cx| {
            let new_value = serde_json::Value::Bool(match toggle_state {
                ToggleState::Indeterminate => {
                    return;
                }
                ToggleState::Selected => true,
                ToggleState::Unselected => false,
            });

            SettingsValue::write_value(&path, new_value, cx);
        },
    )
    .into_any_element()
}

fn render_toggle_button_group(
    value: SettingsValue<serde_json::Value>,
    variants: &'static [&'static str],
    labels: &'static [&'static str],
    _: &mut Window,
    _: &mut App,
) -> AnyElement {
    let value = downcast_any_item::<String>(value);

    fn make_toggle_group<const LEN: usize>(
        group_name: &'static str,
        value: SettingsValue<String>,
        variants: &'static [&'static str],
        labels: &'static [&'static str],
    ) -> AnyElement {
        let mut variants_array: [(&'static str, &'static str); LEN] = [("unused", "unused"); LEN];
        for i in 0..LEN {
            variants_array[i] = (variants[i], labels[i]);
        }
        let active_value = value.read();

        let selected_idx = variants_array
            .iter()
            .enumerate()
            .find_map(|(idx, (variant, _))| {
                if variant == &active_value {
                    Some(idx)
                } else {
                    None
                }
            });

        let mut idx = 0;
        ToggleButtonGroup::single_row(
            group_name,
            variants_array.map(|(variant, label)| {
                let path = value.path.clone();
                idx += 1;
                ToggleButtonSimple::new(label, move |_, _, cx| {
                    SettingsValue::write_value(
                        &path,
                        serde_json::Value::String(variant.to_string()),
                        cx,
                    );
                })
            }),
        )
        .when_some(selected_idx, |this, ix| this.selected_index(ix))
        .style(ui::ToggleButtonGroupStyle::Filled)
        .into_any_element()
    }

    macro_rules! templ_toggl_with_const_param {
        ($len:expr) => {
            if variants.len() == $len {
                return make_toggle_group::<$len>(value.title, value, variants, labels);
            }
        };
    }
    templ_toggl_with_const_param!(1);
    templ_toggl_with_const_param!(2);
    templ_toggl_with_const_param!(3);
    templ_toggl_with_const_param!(4);
    templ_toggl_with_const_param!(5);
    templ_toggl_with_const_param!(6);
    unreachable!("Too many variants");
}

fn settings_value_from_settings_and_path(
    path: SmallVec<[&'static str; 1]>,
    title: &'static str,
    user_settings: &serde_json::Value,
    default_settings: &serde_json::Value,
) -> SettingsValue<serde_json::Value> {
    let default_value = read_settings_value_from_path(default_settings, &path)
        .with_context(|| format!("No default value for item at path {:?}", path.join(".")))
        .expect("Default value set for item")
        .clone();

    let value = read_settings_value_from_path(user_settings, &path).cloned();
    let settings_value = SettingsValue {
        default_value,
        value,
        path: path.clone(),
        // todo(settings_ui) is title required inside SettingsValue?
        title,
    };
    return settings_value;
}