use ratatui::buffer::Buffer;
use ratatui::layout::Rect;
use ratatui::widgets::WidgetRef;

use super::popup_consts::MAX_POPUP_ROWS;
use super::scroll_state::ScrollState;
use super::selection_popup_common::GenericDisplayRow;
use super::selection_popup_common::render_rows;
use super::slash_commands;
use crate::product::protocol::custom_prompts::CustomPrompt;
use crate::product::protocol::custom_prompts::PROMPTS_CMD_PREFIX;
use crate::product::tui_app::render::Insets;
use crate::product::tui_app::render::RectExt;
use crate::product::tui_app::slash_command::SlashCommand;
use std::collections::HashSet;

// Hide alias commands in the default popup list so each unique action appears once.
// `quit` is an alias of `exit`, so we skip `quit` here.
// `approvals` is an alias of `permissions`.
const ALIAS_COMMANDS: &[SlashCommand] = &[SlashCommand::Quit, SlashCommand::Approvals];

/// A selectable item in the popup: either a built-in command or a user prompt.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub(crate) enum CommandItem {
    Builtin(SlashCommand),
    // Index into `prompts`
    UserPrompt(usize),
}

pub(crate) struct CommandPopup {
    command_filter: String,
    builtins: Vec<(&'static str, SlashCommand)>,
    prompts: Vec<CustomPrompt>,
    state: ScrollState,
}

#[derive(Clone, Copy, Debug, Default)]
pub(crate) struct CommandPopupFlags {
    pub(crate) identities_enabled: bool,
    pub(crate) personality_command_enabled: bool,
    pub(crate) windows_degraded_sandbox_active: bool,
}

impl CommandPopup {
    pub(crate) fn new(mut prompts: Vec<CustomPrompt>, flags: CommandPopupFlags) -> Self {
        // Keep built-in availability in sync with the composer.
        let builtins = slash_commands::builtins_for_input(
            flags.identities_enabled,
            flags.personality_command_enabled,
            flags.windows_degraded_sandbox_active,
        );
        // Exclude prompts that collide with builtin command names and sort by name.
        let exclude: HashSet<String> = builtins.iter().map(|(n, _)| (*n).to_string()).collect();
        prompts.retain(|p| !exclude.contains(&p.name));
        prompts.sort_by(|a, b| a.name.cmp(&b.name));
        Self {
            command_filter: String::new(),
            builtins,
            prompts,
            state: ScrollState::new(),
        }
    }

    pub(crate) fn set_prompts(&mut self, mut prompts: Vec<CustomPrompt>) {
        let exclude: HashSet<String> = self
            .builtins
            .iter()
            .map(|(n, _)| (*n).to_string())
            .collect();
        prompts.retain(|p| !exclude.contains(&p.name));
        prompts.sort_by(|a, b| a.name.cmp(&b.name));
        self.prompts = prompts;
    }

    pub(crate) fn prompt(&self, idx: usize) -> Option<&CustomPrompt> {
        self.prompts.get(idx)
    }

    /// Update the filter string based on the current composer text. The text
    /// passed in is expected to start with a leading '/'. Everything after the
    /// *first* '/' on the *first* line becomes the active filter that is used
    /// to narrow down the list of available commands.
    pub(crate) fn on_composer_text_change(&mut self, text: String) {
        let first_line = text.lines().next().unwrap_or("");

        if let Some(stripped) = first_line.strip_prefix('/') {
            // Extract the *first* token (sequence of non-whitespace
            // characters) after the slash so that `/clear something` still
            // shows the help for `/clear`.
            let token = stripped.trim_start();
            let cmd_token = token.split_whitespace().next().unwrap_or("");

            // Update the filter keeping the original case (commands are all
            // lower-case for now but this may change in the future).
            self.command_filter = cmd_token.to_string();
        } else {
            // The composer no longer starts with '/'. Reset the filter so the
            // popup shows the *full* command list if it is still displayed
            // for some reason.
            self.command_filter.clear();
        }

        // Reset or clamp selected index based on new filtered list.
        let matches_len = self.filtered_items().len();
        self.state.clamp_selection(matches_len);
        self.state
            .ensure_visible(matches_len, MAX_POPUP_ROWS.min(matches_len));
    }

    /// Determine the preferred height of the popup for a given width.
    /// Accounts for wrapped descriptions so that long tooltips don't overflow.
    pub(crate) fn calculate_required_height(&self, width: u16) -> u16 {
        use super::selection_popup_common::measure_rows_height;
        let rows = self.rows_from_matches(self.filtered());

        measure_rows_height(&rows, &self.state, MAX_POPUP_ROWS, width)
    }

    /// Compute exact/prefix matches over built-in commands and user prompts,
    /// paired with optional highlight indices. Preserves the original
    /// presentation order for built-ins and prompts.
    fn filtered(&self) -> Vec<(CommandItem, Option<Vec<usize>>)> {
        let filter = self.command_filter.trim();
        let mut out: Vec<(CommandItem, Option<Vec<usize>>)> = Vec::new();
        if filter.is_empty() {
            // Built-ins first, in presentation order.
            for (_, cmd) in self.builtins.iter() {
                if ALIAS_COMMANDS.contains(cmd) {
                    continue;
                }
                out.push((CommandItem::Builtin(*cmd), None));
            }
            // Then prompts, already sorted by name.
            for idx in 0..self.prompts.len() {
                out.push((CommandItem::UserPrompt(idx), None));
            }
            return out;
        }

        let filter_lower = filter.to_lowercase();
        let filter_chars = filter.chars().count();
        let mut exact: Vec<(CommandItem, Option<Vec<usize>>)> = Vec::new();
        let mut prefix: Vec<(CommandItem, Option<Vec<usize>>)> = Vec::new();
        let prompt_prefix_len = PROMPTS_CMD_PREFIX.chars().count() + 1;
        let indices_for = |offset| Some((offset..offset + filter_chars).collect());

        let mut push_match =
            |item: CommandItem, display: &str, name: Option<&str>, name_offset: usize| {
                let display_lower = display.to_lowercase();
                let name_lower = name.map(str::to_lowercase);
                let display_exact = display_lower == filter_lower;
                let name_exact = name_lower.as_deref() == Some(filter_lower.as_str());
                if display_exact || name_exact {
                    let offset = if display_exact { 0 } else { name_offset };
                    exact.push((item, indices_for(offset)));
                    return;
                }
                let display_prefix = display_lower.starts_with(&filter_lower);
                let name_prefix = name_lower
                    .as_ref()
                    .is_some_and(|name| name.starts_with(&filter_lower));
                if display_prefix || name_prefix {
                    let offset = if display_prefix { 0 } else { name_offset };
                    prefix.push((item, indices_for(offset)));
                }
            };

        for (_, cmd) in self.builtins.iter() {
            push_match(CommandItem::Builtin(*cmd), cmd.command(), None, 0);
        }
        // Support both search styles:
        // - Typing "name" should surface "/prompts:name" results.
        // - Typing "prompts:name" should also work.
        for (idx, p) in self.prompts.iter().enumerate() {
            let display = format!("{PROMPTS_CMD_PREFIX}:{}", p.name);
            push_match(
                CommandItem::UserPrompt(idx),
                &display,
                Some(&p.name),
                prompt_prefix_len,
            );
        }

        out.extend(exact);
        out.extend(prefix);
        out
    }

    fn filtered_items(&self) -> Vec<CommandItem> {
        self.filtered().into_iter().map(|(c, _)| c).collect()
    }

    fn rows_from_matches(
        &self,
        matches: Vec<(CommandItem, Option<Vec<usize>>)>,
    ) -> Vec<GenericDisplayRow> {
        matches
            .into_iter()
            .map(|(item, indices)| {
                let (name, description) = match item {
                    CommandItem::Builtin(cmd) => {
                        (format!("/{}", cmd.command()), cmd.description().to_string())
                    }
                    CommandItem::UserPrompt(i) => {
                        let prompt = &self.prompts[i];
                        let description = prompt
                            .description
                            .clone()
                            .unwrap_or_else(|| "send saved prompt".to_string());
                        (
                            format!("/{PROMPTS_CMD_PREFIX}:{}", prompt.name),
                            description,
                        )
                    }
                };
                GenericDisplayRow {
                    name,
                    match_indices: indices.map(|v| v.into_iter().map(|i| i + 1).collect()),
                    display_shortcut: None,
                    description: Some(description),
                    wrap_indent: None,
                    is_disabled: false,
                    disabled_reason: None,
                }
            })
            .collect()
    }

    /// Move the selection cursor one step up.
    pub(crate) fn move_up(&mut self) {
        let len = self.filtered_items().len();
        self.state.move_up_wrap(len);
        self.state.ensure_visible(len, MAX_POPUP_ROWS.min(len));
    }

    /// Move the selection cursor one step down.
    pub(crate) fn move_down(&mut self) {
        let matches_len = self.filtered_items().len();
        self.state.move_down_wrap(matches_len);
        self.state
            .ensure_visible(matches_len, MAX_POPUP_ROWS.min(matches_len));
    }

    /// Return currently selected command, if any.
    pub(crate) fn selected_item(&self) -> Option<CommandItem> {
        let matches = self.filtered_items();
        self.state
            .selected_idx
            .and_then(|idx| matches.get(idx).copied())
    }
}

impl WidgetRef for CommandPopup {
    fn render_ref(&self, area: Rect, buf: &mut Buffer) {
        let rows = self.rows_from_matches(self.filtered());
        render_rows(
            area.inset(Insets::tlbr(0, 2, 0, 0)),
            buf,
            &rows,
            &self.state,
            MAX_POPUP_ROWS,
            "no matches",
        );
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use pretty_assertions::assert_eq;

    #[test]
    fn filter_includes_init_when_typing_prefix() {
        let mut popup = CommandPopup::new(Vec::new(), CommandPopupFlags::default());
        // Simulate the composer line starting with '/in' so the popup filters
        // matching commands by prefix.
        popup.on_composer_text_change("/in".to_string());

        // Access the filtered list via the selected command and ensure that
        // one of the matches is the new "init" command.
        let matches = popup.filtered_items();
        let has_init = matches.iter().any(|item| match item {
            CommandItem::Builtin(cmd) => cmd.command() == "init",
            CommandItem::UserPrompt(_) => false,
        });
        assert!(
            has_init,
            "expected '/init' to appear among filtered commands"
        );
    }

    #[test]
    fn selecting_init_by_exact_match() {
        let mut popup = CommandPopup::new(Vec::new(), CommandPopupFlags::default());
        popup.on_composer_text_change("/init".to_string());

        // When an exact match exists, the selected command should be that
        // command by default.
        let selected = popup.selected_item();
        match selected {
            Some(CommandItem::Builtin(cmd)) => assert_eq!(cmd.command(), "init"),
            Some(CommandItem::UserPrompt(_)) => panic!("unexpected prompt selected for '/init'"),
            None => panic!("expected a selected command for exact match"),
        }
    }

    #[test]
    fn model_is_first_suggestion_for_mo() {
        let mut popup = CommandPopup::new(Vec::new(), CommandPopupFlags::default());
        popup.on_composer_text_change("/mo".to_string());
        let matches = popup.filtered_items();
        match matches.first() {
            Some(CommandItem::Builtin(cmd)) => assert_eq!(cmd.command(), "model"),
            Some(CommandItem::UserPrompt(_)) => {
                panic!("unexpected prompt ranked before '/model' for '/mo'")
            }
            None => panic!("expected at least one match for '/mo'"),
        }
    }

    #[test]
    fn filtered_commands_keep_presentation_order_for_prefix() {
        let mut popup = CommandPopup::new(Vec::new(), CommandPopupFlags::default());
        popup.on_composer_text_change("/m".to_string());

        let cmds: Vec<&str> = popup
            .filtered_items()
            .into_iter()
            .filter_map(|item| match item {
                CommandItem::Builtin(cmd) => Some(cmd.command()),
                CommandItem::UserPrompt(_) => None,
            })
            .collect();
        assert_eq!(cmds, vec!["model", "memories", "mention", "mcp"]);
    }

    #[test]
    fn prompt_discovery_lists_custom_prompts() {
        let prompts = vec![
            CustomPrompt {
                name: "foo".to_string(),
                path: "/tmp/foo.md".to_string().into(),
                content: "hello from foo".to_string(),
                description: None,
                argument_hint: None,
            },
            CustomPrompt {
                name: "bar".to_string(),
                path: "/tmp/bar.md".to_string().into(),
                content: "hello from bar".to_string(),
                description: None,
                argument_hint: None,
            },
        ];
        let popup = CommandPopup::new(prompts, CommandPopupFlags::default());
        let items = popup.filtered_items();
        let mut prompt_names: Vec<String> = items
            .into_iter()
            .filter_map(|it| match it {
                CommandItem::UserPrompt(i) => popup.prompt(i).map(|p| p.name.clone()),
                _ => None,
            })
            .collect();
        prompt_names.sort();
        assert_eq!(prompt_names, vec!["bar".to_string(), "foo".to_string()]);
    }

    #[test]
    fn prompt_name_collision_with_builtin_is_ignored() {
        // Create a prompt named like a builtin (e.g. "init").
        let popup = CommandPopup::new(
            vec![CustomPrompt {
                name: "init".to_string(),
                path: "/tmp/init.md".to_string().into(),
                content: "should be ignored".to_string(),
                description: None,
                argument_hint: None,
            }],
            CommandPopupFlags::default(),
        );
        let items = popup.filtered_items();
        let has_collision_prompt = items.into_iter().any(|it| match it {
            CommandItem::UserPrompt(i) => popup.prompt(i).is_some_and(|p| p.name == "init"),
            _ => false,
        });
        assert!(
            !has_collision_prompt,
            "prompt with builtin name should be ignored"
        );
    }

    #[test]
    fn prompt_description_uses_frontmatter_metadata() {
        let popup = CommandPopup::new(
            vec![CustomPrompt {
                name: "draftpr".to_string(),
                path: "/tmp/draftpr.md".to_string().into(),
                content: "body".to_string(),
                description: Some("Create feature branch, commit and open draft PR.".to_string()),
                argument_hint: None,
            }],
            CommandPopupFlags::default(),
        );
        let rows = popup.rows_from_matches(vec![(CommandItem::UserPrompt(0), None)]);
        let description = rows.first().and_then(|row| row.description.as_deref());
        assert_eq!(
            description,
            Some("Create feature branch, commit and open draft PR.")
        );
    }

    #[test]
    fn prompt_description_falls_back_when_missing() {
        let popup = CommandPopup::new(
            vec![CustomPrompt {
                name: "foo".to_string(),
                path: "/tmp/foo.md".to_string().into(),
                content: "body".to_string(),
                description: None,
                argument_hint: None,
            }],
            CommandPopupFlags::default(),
        );
        let rows = popup.rows_from_matches(vec![(CommandItem::UserPrompt(0), None)]);
        let description = rows.first().and_then(|row| row.description.as_deref());
        assert_eq!(description, Some("send saved prompt"));
    }

    #[test]
    fn prefix_filter_limits_matches_for_ac() {
        let mut popup = CommandPopup::new(Vec::new(), CommandPopupFlags::default());
        popup.on_composer_text_change("/ac".to_string());

        let cmds: Vec<&str> = popup
            .filtered_items()
            .into_iter()
            .filter_map(|item| match item {
                CommandItem::Builtin(cmd) => Some(cmd.command()),
                CommandItem::UserPrompt(_) => None,
            })
            .collect();
        assert!(
            !cmds.contains(&"compact"),
            "expected prefix search for '/ac' to exclude 'compact', got {cmds:?}"
        );
    }

    #[test]
    fn quit_hidden_in_empty_filter_but_shown_for_prefix() {
        let mut popup = CommandPopup::new(Vec::new(), CommandPopupFlags::default());
        popup.on_composer_text_change("/".to_string());
        let items = popup.filtered_items();
        assert!(!items.contains(&CommandItem::Builtin(SlashCommand::Quit)));

        popup.on_composer_text_change("/qu".to_string());
        let items = popup.filtered_items();
        assert!(items.contains(&CommandItem::Builtin(SlashCommand::Quit)));
    }

    #[test]
    fn identity_command_hidden_when_identities_disabled() {
        let mut popup = CommandPopup::new(Vec::new(), CommandPopupFlags::default());
        popup.on_composer_text_change("/".to_string());

        let cmds: Vec<&str> = popup
            .filtered_items()
            .into_iter()
            .filter_map(|item| match item {
                CommandItem::Builtin(cmd) => Some(cmd.command()),
                CommandItem::UserPrompt(_) => None,
            })
            .collect();
        assert!(
            !cmds.contains(&"identity"),
            "expected '/identity' to be hidden when identities are disabled, got {cmds:?}"
        );
    }

    #[test]
    fn identity_command_visible_when_identities_enabled() {
        let mut popup = CommandPopup::new(
            Vec::new(),
            CommandPopupFlags {
                identities_enabled: true,
                personality_command_enabled: true,
                windows_degraded_sandbox_active: false,
            },
        );
        popup.on_composer_text_change("/identity".to_string());

        match popup.selected_item() {
            Some(CommandItem::Builtin(cmd)) => assert_eq!(cmd.command(), "identity"),
            other => panic!("expected identity to be selected for exact match, got {other:?}"),
        }
    }

    #[test]
    fn personality_command_hidden_when_disabled() {
        let mut popup = CommandPopup::new(
            Vec::new(),
            CommandPopupFlags {
                identities_enabled: true,
                personality_command_enabled: false,
                windows_degraded_sandbox_active: false,
            },
        );
        popup.on_composer_text_change("/pers".to_string());

        let cmds: Vec<&str> = popup
            .filtered_items()
            .into_iter()
            .filter_map(|item| match item {
                CommandItem::Builtin(cmd) => Some(cmd.command()),
                CommandItem::UserPrompt(_) => None,
            })
            .collect();
        assert!(
            !cmds.contains(&"personality"),
            "expected '/personality' to be hidden when disabled, got {cmds:?}"
        );
    }

    #[test]
    fn personality_command_visible_when_enabled() {
        let mut popup = CommandPopup::new(
            Vec::new(),
            CommandPopupFlags {
                identities_enabled: true,
                personality_command_enabled: true,
                windows_degraded_sandbox_active: false,
            },
        );
        popup.on_composer_text_change("/personality".to_string());

        match popup.selected_item() {
            Some(CommandItem::Builtin(cmd)) => assert_eq!(cmd.command(), "personality"),
            other => panic!("expected personality to be selected for exact match, got {other:?}"),
        }
    }
}
