// path_from_the_root: src/orchestrator/router.rs

extern crate alloc;

use alloc::string::String;
use alloc::vec::Vec;

#[cfg(feature = "alloc")]
use hashbrown::HashMap;

use crate::component::Component;
use crate::focus::{FocusError, FocusManager};

#[derive(Debug, Clone)]
pub enum RouterEvent {
    Navigated { from: Option<String>, to: String },
    Back { to: String },
    Forward { to: String },
}

pub struct Router<C: Component> {
    #[cfg(feature = "alloc")]
    pages: HashMap<String, C>,
    #[cfg(not(feature = "alloc"))]
    pages: Vec<(String, C)>,
    current: Option<String>,
    history: Vec<String>,
    future: Vec<String>,
    focus: FocusManager<C::Focus>,
}

impl<C: Component> Default for Router<C> {
    fn default() -> Self {
        Self::new()
    }
}

impl<C: Component> Router<C> {
    pub fn new() -> Self {
        Self {
            #[cfg(feature = "alloc")]
            pages: HashMap::new(),
            #[cfg(not(feature = "alloc"))]
            pages: Vec::new(),
            current: None,
            history: Vec::new(),
            future: Vec::new(),
            focus: FocusManager::new(),
        }
    }

    pub fn register(&mut self, id: String, mut page: C) {
        #[cfg(feature = "alloc")]
        {
            if self.current.as_ref() == Some(&id) {
                let _ = page.on_enter();
                let targets = page.targets();
                self.focus.set_targets(targets.to_vec());
            }
            self.pages.insert(id, page);
        }

        #[cfg(not(feature = "alloc"))]
        {
            if self.current.as_ref() == Some(&id) {
                let _ = page.on_enter();
                let targets = page.targets();
                self.focus.set_targets(targets.to_vec());
            }
            self.pages.push((id, page));
        }
    }

    fn get_page_mut(&mut self, id: &str) -> Option<&mut C> {
        #[cfg(feature = "alloc")]
        {
            self.pages.get_mut(id)
        }

        #[cfg(not(feature = "alloc"))]
        {
            self.pages
                .iter_mut()
                .find(|(page_id, _)| page_id == id)
                .map(|(_, page)| page)
        }
    }

    fn get_page(&self, id: &str) -> Option<&C> {
        #[cfg(feature = "alloc")]
        {
            self.pages.get(id)
        }

        #[cfg(not(feature = "alloc"))]
        {
            self.pages
                .iter()
                .find(|(page_id, _)| page_id == id)
                .map(|(_, page)| page)
        }
    }

    pub fn navigate(&mut self, id: String) -> Result<Option<RouterEvent>, FocusError> {
        let result = if let Some(current_id) = self.current.take() {
            if let Some(current_page) = self.get_page_mut(&current_id) {
                let _ = current_page.on_exit();
            }
            self.history.push(current_id.clone());
            self.future.clear();
            Some(RouterEvent::Navigated {
                from: Some(current_id),
                to: id.clone(),
            })
        } else {
            Some(RouterEvent::Navigated {
                from: None,
                to: id.clone(),
            })
        };

        let targets = if let Some(page) = self.get_page_mut(&id) {
            let _ = page.on_enter();
            Some(page.targets().to_vec())
        } else {
            None
        };

        if let Some(targets) = targets {
            self.focus.set_targets(targets);
        }

        self.current = Some(id);
        Ok(result)
    }

    pub fn back(&mut self) -> Result<Option<RouterEvent>, FocusError> {
        if let Some(current) = self.current.take() {
            if let Some(from) = self.history.pop() {
                self.future.push(current.clone());
                let to = from.clone();

                if let Some(current_page) = self.get_page_mut(&current) {
                    let _ = current_page.on_exit();
                }

                self.current = Some(to.clone());

                let targets = if let Some(page) = self.get_page_mut(&to) {
                    let _ = page.on_enter();
                    Some(page.targets().to_vec())
                } else {
                    None
                };

                if let Some(targets) = targets {
                    self.focus.set_targets(targets);
                }

                Ok(Some(RouterEvent::Back { to }))
            } else {
                self.current = Some(current);
                Ok(None)
            }
        } else {
            Ok(None)
        }
    }

    pub fn forward(&mut self) -> Result<Option<RouterEvent>, FocusError> {
        if let Some(current) = self.current.take() {
            if let Some(from) = self.future.pop() {
                self.history.push(current.clone());
                let to = from.clone();

                if let Some(current_page) = self.get_page_mut(&current) {
                    let _ = current_page.on_exit();
                }

                self.current = Some(to.clone());

                let targets = if let Some(page) = self.get_page_mut(&to) {
                    let _ = page.on_enter();
                    Some(page.targets().to_vec())
                } else {
                    None
                };

                if let Some(targets) = targets {
                    self.focus.set_targets(targets);
                }

                Ok(Some(RouterEvent::Forward { to }))
            } else {
                self.current = Some(current);
                Ok(None)
            }
        } else {
            Ok(None)
        }
    }

    pub fn current(&self) -> Option<&C> {
        self.current.as_ref().and_then(|id| self.get_page(id))
    }

    pub fn current_mut(&mut self) -> Option<&mut C> {
        if let Some(id) = self.current.clone() {
            self.get_page_mut(&id)
        } else {
            None
        }
    }

    pub fn current_id(&self) -> Option<&String> {
        self.current.as_ref()
    }

    pub fn focus_manager(&self) -> &FocusManager<C::Focus> {
        &self.focus
    }

    pub fn focus_manager_mut(&mut self) -> &mut FocusManager<C::Focus> {
        &mut self.focus
    }

    pub fn history(&self) -> &[String] {
        &self.history
    }

    pub fn future(&self) -> &[String] {
        &self.future
    }

    pub fn page_count(&self) -> usize {
        #[cfg(feature = "alloc")]
        {
            self.pages.len()
        }
        #[cfg(not(feature = "alloc"))]
        {
            self.pages.len()
        }
    }

    pub fn has_page(&self, id: &str) -> bool {
        #[cfg(feature = "alloc")]
        {
            self.pages.contains_key(id)
        }
        #[cfg(not(feature = "alloc"))]
        {
            self.pages.iter().any(|(page_id, _)| page_id == id)
        }
    }
}