use std::ops::Deref;
use std::sync::{Mutex, MutexGuard};
use std::sync::Arc;

use cursive::{Printer, Vec2, With, XY};
use cursive::align::*;
use cursive::theme::StyleType;
use cursive::utils::lines::spans::{LinesIterator, Row};
use cursive::utils::markup::StyledString;
use cursive::view::{SizeCache, View};
use owning_ref::{ArcRef, OwningHandle};
use unicode_width::UnicodeWidthStr;

// Content type used internally for caching and storage
type InnerContentType = Arc<StyledString>;

/// Provides access to the content of a [`TextView`].
///
/// [`TextView`]: struct.TextView.html
///
/// Cloning this object will still point to the same content.
///
/// # Examples
///
/// ```rust
/// # use cursive::views::{TextView, TextContent};
/// let mut content = TextContent::new("content");
/// let view = TextView::new_with_content(content.clone());
///
/// // Later, possibly in a different thread
/// content.set_content("new content");
/// assert!(view.get_content().source().contains("new"));
/// ```
#[derive(Clone)]
pub struct TextContent {
    content: Arc<Mutex<TextContentInner>>,
}

impl TextContent {
    /// Creates a new text content around the given value.
    ///
    /// Parses the given value.
    pub fn new<S>(content: S) -> Self
        where
            S: Into<StyledString>,
    {
        let content = Arc::new(content.into());

        TextContent {
            content: Arc::new(Mutex::new(TextContentInner {
                content_value: content,
                content_cache: Arc::new(StyledString::default()),
                size_cache: None,
            })),
        }
    }
}

/// A reference to the text content.
///
/// This can be deref'ed into a [`StyledString`].
///
/// [`StyledString`]: ../utils/markup/type.StyledString.html
///
/// This keeps the content locked. Do not store this!
pub struct TextContentRef {
    _handle: OwningHandle<
        ArcRef<Mutex<TextContentInner>>,
        MutexGuard<'static, TextContentInner>,
    >,
    // We also need to keep a copy of Arc so `deref` can return
    // a reference to the `StyledString`
    data: Arc<StyledString>,
}

impl Deref for TextContentRef {
    type Target = StyledString;

    fn deref(&self) -> &StyledString {
        self.data.as_ref()
    }
}

impl TextContent {
    /// Replaces the content with the given value.
    pub fn set_content<S>(&self, content: S)
        where
            S: Into<StyledString>,
    {
        self.with_content(|c| {
            *c = content.into();
        });
    }

    /// Append `content` to the end of a `TextView`.
    pub fn append<S>(&self, content: S)
        where
            S: Into<StyledString>,
    {
        self.with_content(|c| {
            // This will only clone content if content_cached and content_value
            // are sharing the same underlying Rc.
            c.append(content);
        })
    }

    /// Returns a reference to the content.
    ///
    /// This locks the data while the returned value is alive,
    /// so don't keep it too long.
    pub fn get_content(&self) -> TextContentRef {
        TextContentInner::get_content(&self.content)
    }

    /// Apply the given closure to the inner content, and bust the cache afterward.
    pub fn with_content<F, O>(&self, f: F) -> O
        where
            F: FnOnce(&mut StyledString) -> O,
    {
        self.with_content_inner(|c| f(Arc::make_mut(&mut c.content_value)))
    }

    /// Apply the given closure to the inner content, and bust the cache afterward.
    fn with_content_inner<F, O>(&self, f: F) -> O
        where
            F: FnOnce(&mut TextContentInner) -> O,
    {
        let mut content = self.content.lock().unwrap();

        let out = f(&mut content);

        content.size_cache = None;

        out
    }
}

/// Internel representation of the content for a `TextView`.
///
/// This is mostly just a `StyledString`.
///
/// Can be shared (through a `Arc<Mutex>`).
struct TextContentInner {
    // content: String,
    content_value: InnerContentType,
    content_cache: InnerContentType,

    // We keep the cache here so it can be busted when we change the content.
    size_cache: Option<XY<SizeCache>>,
}

impl TextContentInner {
    /// From a shareable content (Arc + Mutex), return a
    fn get_content(content: &Arc<Mutex<TextContentInner>>) -> TextContentRef {
        let arc_ref: ArcRef<Mutex<TextContentInner>> =
            ArcRef::new(Arc::clone(content));

        let _handle = OwningHandle::new_with_fn(arc_ref, |mutex| unsafe {
            (*mutex).lock().unwrap()
        });

        let data = Arc::clone(&_handle.content_value);

        TextContentRef { _handle, data }
    }

    fn is_cache_valid(&self, size: Vec2) -> bool {
        match self.size_cache {
            None => false,
            Some(ref last) => last.x.accept(size.x) && last.y.accept(size.y),
        }
    }

    fn get_cache(&self) -> &InnerContentType {
        &self.content_cache
    }
}

/// A simple view showing a fixed text.
///
/// # Examples
///
/// ```rust
/// use cursive::Cursive;
/// use cursive_cached_text_view::CachedTextView;
/// use cursive_core::Cursive;
/// let mut siv = Cursive::new();
///
/// siv.add_layer(CachedTextView::new("Hello world!", 5));
/// ```
pub struct CachedTextView {
    cache: TinyCache<usize, Vec<Row>>,
    content: TextContent,

    align: Align,

    style: StyleType,

    // True if we can wrap long lines.
    wrap: bool,

    // ScrollBase make many scrolling-related things easier
    width: Option<usize>,
}

impl CachedTextView {
    /// Creates a new TextView with the given content.
    pub fn new<S>(content: S, cache_size: usize) -> Self
        where
            S: Into<StyledString>,
    {
        Self::new_with_content(TextContent::new(content), cache_size)
    }

    /// Creates a new TextView using the given `TextContent`.
    ///
    /// If you kept a clone of the given content, you'll be able to update it
    /// remotely.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use cursive_cached_text_view::{TextContent, CachedTextView};
    /// let mut content = TextContent::new("content");
    /// let view = CachedTextView::new_with_content(content.clone(), 5);
    ///
    /// // Later, possibly in a different thread
    /// content.set_content("new content");
    /// assert!(view.get_content().source().contains("new"));
    /// ```
    pub fn new_with_content(content: TextContent, cache_size: usize) -> Self {
        CachedTextView {
            cache: TinyCache::new(cache_size),
            content,
            style: StyleType::default(),
            wrap: true,
            align: Align::top_left(),
            width: None,
        }
    }

    /// Creates a new empty `TextView`.
    pub fn empty() -> Self {
        CachedTextView::new("", 5)
    }

    /// Sets the style for the content.
    pub fn set_style<S: Into<StyleType>>(&mut self, style: S) {
        self.style = style.into();
    }

    /// Sets the style for the entire content.
    ///
    /// Chainable variant.
    #[must_use]
    pub fn style<S: Into<StyleType>>(self, style: S) -> Self {
        self.with(|s| s.set_style(style))
    }

    /// Disables content wrap for this view.
    ///
    /// This may be useful if you want horizontal scrolling.
    #[must_use]
    pub fn no_wrap(self) -> Self {
        self.with(|s| s.set_content_wrap(false))
    }

    /// Controls content wrap for this view.
    ///
    /// If `true` (the default), text will wrap long lines when needed.
    pub fn set_content_wrap(&mut self, wrap: bool) {
        self.wrap = wrap;
    }

    /// Sets the horizontal alignment for this view.
    #[must_use]
    pub fn h_align(mut self, h: HAlign) -> Self {
        self.align.h = h;

        self
    }

    /// Sets the vertical alignment for this view.
    #[must_use]
    pub fn v_align(mut self, v: VAlign) -> Self {
        self.align.v = v;

        self
    }

    /// Sets the alignment for this view.
    #[must_use]
    pub fn align(mut self, a: Align) -> Self {
        self.align = a;

        self
    }

    /// Center the text horizontally and vertically inside the view.
    #[must_use]
    pub fn center(mut self) -> Self {
        self.align = Align::center();
        self
    }

    /// Replace the text in this view.
    ///
    /// Chainable variant.
    #[must_use]
    pub fn content<S>(self, content: S) -> Self
        where
            S: Into<StyledString>,
    {
        self.with(|s| s.set_content(content))
    }

    /// Replace the text in this view.
    pub fn set_content<S>(&mut self, content: S)
        where
            S: Into<StyledString>,
    {
        self.content.set_content(content);
    }

    /// Append `content` to the end of a `TextView`.
    pub fn append<S>(&mut self, content: S)
        where
            S: Into<StyledString>,
    {
        self.content.append(content);
    }

    /// Returns the current text in this view.
    pub fn get_content(&self) -> TextContentRef {
        TextContentInner::get_content(&self.content.content)
    }

    /// Returns a shared reference to the content, allowing content mutation.
    pub fn get_shared_content(&mut self) -> TextContent {
        // We take &mut here without really needing it,
        // because it sort of "makes sense".
        TextContent {
            content: Arc::clone(&self.content.content),
        }
    }

    // This must be non-destructive, as it may be called
    // multiple times during layout.
    fn compute_rows(&mut self, size: Vec2) {
        let size = if self.wrap { size } else { Vec2::max_value() };

        let mut content = self.content.content.lock().unwrap();
        if content.is_cache_valid(size) {
            return;
        }

        // Completely bust the cache
        // Just in case we fail, we don't want to leave a bad cache.
        content.size_cache = None;
        content.content_cache = Arc::clone(&content.content_value);

        let rows = self.cache.compute(size.x, || {
            LinesIterator::new(content.get_cache().as_ref(), size.x).collect()
        });

        // Desired width
        self.width = if rows.iter().any(|row| row.is_wrapped) {
            // If any rows are wrapped, then require the full width.
            Some(size.x)
        } else {
            rows.iter().map(|row| row.width).max()
        }
    }
}

impl View for CachedTextView {
    fn draw(&self, printer: &Printer) {
        let rows = if let Some(rows) = self.cache.last() {
            rows
        } else {
            return;
        };
        let h = rows.len();
        // If the content is smaller than the view, align it somewhere.
        let offset = self.align.v.get_offset(h, printer.size.y);
        let printer = &printer.offset((0, offset));

        let content = self.content.content.lock().unwrap();

        printer.with_style(self.style, |printer| {
            for (y, row) in rows
                .iter()
                .enumerate()
                .skip(printer.content_offset.y)
                .take(printer.output_size.y)
            {
                let l = row.width;
                let mut x = self.align.h.get_offset(l, printer.size.x);

                for span in row.resolve_stream(content.get_cache().as_ref()) {
                    printer.with_style(*span.attr, |printer| {
                        printer.print((x, y), span.content);
                        x += span.content.width();
                    });
                }
            }
        });
    }

    fn layout(&mut self, size: Vec2) {
        // Compute the text rows.
        self.compute_rows(size);

        let num_rows = self.cache.last().map(|rows| rows.len()).unwrap_or(0);

        // The entire "virtual" size (includes all rows)
        let my_size = Vec2::new(self.width.unwrap_or(0), num_rows);

        // Build a fresh cache.
        let mut content = self.content.content.lock().unwrap();
        content.size_cache = Some(SizeCache::build(my_size, size));
    }

    fn needs_relayout(&self) -> bool {
        let content = self.content.content.lock().unwrap();
        content.size_cache.is_none()
    }

    fn required_size(&mut self, size: Vec2) -> Vec2 {
        self.compute_rows(size);

        let num_rows = self.cache.last().map(|rows| rows.len()).unwrap_or(0);

        Vec2::new(self.width.unwrap_or(0), num_rows)
    }
}


struct TinyCache<K, V> {
    size: usize,
    data: Vec<(usize, K, V)>,
}

impl<K, V> TinyCache<K, V> {
    fn new(size: usize) -> Self {
        TinyCache {
            size,
            data: Vec::with_capacity(size),
        }
    }

    fn get_key_index(&self, key: &K) -> Option<usize> where K: Eq {
        self.data.iter().rposition(|(_, k, _)| k == key)
    }

    fn compute(&mut self, key: K, f: impl FnOnce() -> V) -> &V where K: Eq {
        if let Some(index) = self.get_key_index(&key) {
            self.data[index].0 += 1;
            return &self.data[index].2;
        }

        let v = f();
        self.clean();
        self.data.push((0, key, v));
        &self.data.last().as_ref().unwrap().2
    }

    fn clean(&mut self) {
        if self.data.len() < self.size {
            return;
        }
        let index = self.data.iter().enumerate()
            .min_by_key(|(_, (count, _, _))| *count)
            .map(|(i, _)| i);

        if let Some(index) = index {
            self.data.swap_remove(index);
        }
    }

    fn last(&self) -> Option<&V> {
        self.data.last().map(|(_, _, v)| v)
    }

    #[cfg(test)]
    fn len(&self) -> usize {
        self.data.len()
    }

    #[cfg(test)]
    fn is_empty(&self) -> bool {
        self.data.is_empty()
    }

    #[cfg(test)]
    fn keys(&self) -> Vec<(&K, usize)> {
        self.data.iter().map(|(count, key, _)| (key, *count)).collect()
    }
}

#[cfg(test)]
mod tests {
    use cursive::Vec2;

    use super::*;

    #[test]
    fn sanity() {
        let text_view = CachedTextView::new("", 5);
        assert_eq!(text_view.get_content().data.spans.len(), 1);
    }

    #[test]
    fn test_cache() {
        let mut text_view = CachedTextView::new("sample", 3);
        assert!(text_view.cache.is_empty());

        text_view.compute_rows(Vec2::new(0, 0));
        assert_eq!(text_view.cache.len(), 1);
        text_view.compute_rows(Vec2::new(0, 0));
        assert_eq!(text_view.cache.len(), 1);

        text_view.compute_rows(Vec2::new(1, 0));
        assert_eq!(text_view.cache.len(), 2);

        text_view.compute_rows(Vec2::new(2, 0));
        assert_eq!(text_view.cache.len(), 3);

        text_view.compute_rows(Vec2::new(3, 0));
        assert_eq!(text_view.cache.len(), 3);

        assert_eq!(text_view.cache.keys(), [(&0, 1), (&2, 0), (&3, 0)]);
    }
}