use gpui::SharedString;

use crate::primitives::IconName;

/// Where a picture sits across its column.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub enum Align {
    Left,
    #[default]
    Center,
    Right,
}

/// A picture, clip or page shown in a block: its address, and its width as a share of the column.
#[derive(Clone, Debug, PartialEq)]
pub struct Media {
    pub source: SharedString,
    pub width: f32,
    pub align: Align,
}

impl Media {
    pub fn new(source: impl Into<SharedString>) -> Self {
        Self {
            source: source.into(),
            width: 1.0,
            align: Align::Center,
        }
    }
}

/// What a block is. Each holds its text in fields: one for most, a title and a body for a toggle, one per column, a caption for media, one per cell for a table, none for a divider.
#[derive(Clone, Debug, PartialEq)]
pub enum BlockKind {
    Paragraph,
    Heading(u8),
    Bullet,
    Numbered,
    Todo(bool),
    Quote,
    Callout,
    /// Open or closed; its body shows while open.
    Toggle(bool),
    Code,
    Math,
    /// Diagram source, such as Mermaid; the host renders the picture.
    Diagram,
    Divider,
    /// Columns across, the header row first; each `merged` cell, as row and column, folds into the cell on its left.
    Table {
        columns: usize,
        merged: Vec<(usize, usize)>,
    },
    Image(Media),
    Video(Media),
    Embed(Media),
    /// Side by side, one field each.
    Columns(usize),
    /// Text shared with every other block synced to the same source.
    Synced(SharedString),
}

impl BlockKind {
    /// Its name in the slash menu.
    pub fn label(&self) -> &'static str {
        match self {
            Self::Paragraph => "Text",
            Self::Heading(1) => "Heading 1",
            Self::Heading(2) => "Heading 2",
            Self::Heading(_) => "Heading 3",
            Self::Bullet => "Bulleted list",
            Self::Numbered => "Numbered list",
            Self::Todo(_) => "To-do",
            Self::Quote => "Quote",
            Self::Callout => "Callout",
            Self::Toggle(_) => "Toggle",
            Self::Code => "Code",
            Self::Math => "Math",
            Self::Diagram => "Diagram",
            Self::Divider => "Divider",
            Self::Table { .. } => "Table",
            Self::Image(_) => "Image",
            Self::Video(_) => "Video",
            Self::Embed(_) => "Embed",
            Self::Columns(_) => "Columns",
            Self::Synced(_) => "Synced block",
        }
    }

    pub fn icon(&self) -> IconName {
        match self {
            Self::Paragraph => IconName::Type,
            Self::Heading(1) => IconName::Heading1,
            Self::Heading(2) => IconName::Heading2,
            Self::Heading(_) => IconName::Heading3,
            Self::Bullet => IconName::List,
            Self::Numbered => IconName::ListOrdered,
            Self::Todo(_) => IconName::ListTodo,
            Self::Quote => IconName::Quote,
            Self::Callout => IconName::Info,
            Self::Toggle(_) => IconName::ChevronRight,
            Self::Code => IconName::Code,
            Self::Math => IconName::SquareFunction,
            Self::Diagram => IconName::Workflow,
            Self::Divider => IconName::Minus,
            Self::Table { .. } => IconName::Table,
            Self::Image(_) => IconName::Image,
            Self::Video(_) => IconName::Video,
            Self::Embed(_) => IconName::Globe,
            Self::Columns(_) => IconName::Columns2,
            Self::Synced(_) => IconName::RefreshCw,
        }
    }

    /// What an empty field of this kind says while it has focus.
    pub fn placeholder(&self) -> &'static str {
        match self {
            Self::Paragraph => "Type '/' for commands",
            Self::Heading(_) => self.label(),
            Self::Bullet | Self::Numbered => "List",
            Self::Todo(_) => "To-do",
            Self::Quote => "Quote",
            Self::Callout | Self::Toggle(_) | Self::Columns(_) | Self::Synced(_) => "Write",
            Self::Code => "Code",
            Self::Math => "A formula in TeX, such as e^{i\\pi} + 1 = 0",
            Self::Diagram => "A diagram in Mermaid, such as graph LR; a --> b",
            Self::Image(_) | Self::Video(_) | Self::Embed(_) => "Add a caption",
            Self::Divider | Self::Table { .. } => "",
        }
    }

    /// How many fields a new block of this kind holds.
    pub fn fields(&self) -> usize {
        match self {
            Self::Divider => 0,
            Self::Toggle(_) => 2,
            Self::Columns(count) => *count,
            Self::Table { columns, .. } => columns * 2,
            _ => 1,
        }
    }

    /// Whether it can hold `count` fields: a table any whole rows past its header, the rest their own number.
    pub fn accepts(&self, count: usize) -> bool {
        match self {
            Self::Table { columns, .. } => {
                *columns > 0 && count >= columns * 2 && count.is_multiple_of(*columns)
            }
            kind => count == kind.fields(),
        }
    }

    /// Whether a field made for this kind serves `other` unchanged: the same highlighter and hint.
    pub(crate) fn same_fields(&self, other: &Self) -> bool {
        std::mem::discriminant(self) == std::mem::discriminant(other)
            && match (self, other) {
                (Self::Heading(one), Self::Heading(two)) => one == two,
                (Self::Synced(one), Self::Synced(two)) => one == two,
                _ => true,
            }
    }

    /// Prose: Enter splits it, Backspace at its start turns it back into text or joins it up.
    pub fn is_prose(&self) -> bool {
        matches!(
            self,
            Self::Paragraph
                | Self::Heading(_)
                | Self::Bullet
                | Self::Numbered
                | Self::Todo(_)
                | Self::Quote
                | Self::Callout
        )
    }

    /// The kind Enter starts after this one: lists go on, the rest return to text.
    pub fn next(&self) -> Self {
        match self {
            Self::Bullet => Self::Bullet,
            Self::Numbered => Self::Numbered,
            Self::Todo(_) => Self::Todo(false),
            _ => Self::Paragraph,
        }
    }

    /// Lines of monospaced source, where Enter breaks a line.
    pub fn is_source(&self) -> bool {
        matches!(self, Self::Code | Self::Math | Self::Diagram)
    }
}

/// The kinds the slash menu offers, in order; media and synced blocks come from their owner.
pub(crate) fn offered() -> Vec<BlockKind> {
    vec![
        BlockKind::Paragraph,
        BlockKind::Heading(1),
        BlockKind::Heading(2),
        BlockKind::Heading(3),
        BlockKind::Bullet,
        BlockKind::Numbered,
        BlockKind::Todo(false),
        BlockKind::Quote,
        BlockKind::Callout,
        BlockKind::Toggle(true),
        BlockKind::Code,
        BlockKind::Math,
        BlockKind::Diagram,
        BlockKind::Divider,
        BlockKind::Table {
            columns: 2,
            merged: Vec::new(),
        },
        BlockKind::Columns(2),
    ]
}

/// The kinds whose name holds `query`, for the slash menu.
pub(crate) fn matching(query: &str) -> Vec<BlockKind> {
    let query = query.to_lowercase();
    offered()
        .into_iter()
        .filter(|kind| kind.label().to_lowercase().contains(&query))
        .collect()
}

/// A paragraph's leading markdown that makes it another kind, and how many bytes it takes; the space after it is typed last.
pub(crate) fn shortcut(text: &str) -> Option<(BlockKind, usize)> {
    let prefixes: [(&str, BlockKind); 11] = [
        ("# ", BlockKind::Heading(1)),
        ("## ", BlockKind::Heading(2)),
        ("### ", BlockKind::Heading(3)),
        ("- ", BlockKind::Bullet),
        ("* ", BlockKind::Bullet),
        ("1. ", BlockKind::Numbered),
        ("[] ", BlockKind::Todo(false)),
        ("[ ] ", BlockKind::Todo(false)),
        ("[x] ", BlockKind::Todo(true)),
        ("> ", BlockKind::Quote),
        ("``` ", BlockKind::Code),
    ];
    if text == "---" {
        return Some((BlockKind::Divider, 3));
    }
    prefixes
        .into_iter()
        .find(|(prefix, _)| text.starts_with(prefix))
        .map(|(prefix, kind)| (kind, prefix.len()))
}

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

    #[test]
    fn markdown_at_a_paragraphs_start_turns_it_into_a_kind() {
        assert_eq!(shortcut("## Lift"), Some((BlockKind::Heading(2), 3)));
        assert_eq!(shortcut("[x] done"), Some((BlockKind::Todo(true), 4)));
        assert_eq!(shortcut("---"), Some((BlockKind::Divider, 3)));
        assert_eq!(shortcut("#hashtag"), None);
        assert_eq!(shortcut("1.5 pages"), None);
    }

    #[test]
    fn the_slash_menu_filters_by_name() {
        let labels: Vec<&str> = matching("head").iter().map(BlockKind::label).collect();
        assert_eq!(labels, ["Heading 1", "Heading 2", "Heading 3"]);
        assert!(matching("zzz").is_empty());
    }

    #[test]
    fn a_table_holds_whole_rows_past_its_header() {
        let table = BlockKind::Table {
            columns: 3,
            merged: Vec::new(),
        };
        assert!(table.accepts(9));
        assert!(!table.accepts(7) && !table.accepts(3));
        assert!(BlockKind::Toggle(true).accepts(2) && !BlockKind::Paragraph.accepts(2));
    }

    #[test]
    fn lists_go_on_and_the_rest_return_to_text() {
        assert_eq!(BlockKind::Todo(true).next(), BlockKind::Todo(false));
        assert_eq!(BlockKind::Heading(1).next(), BlockKind::Paragraph);
    }
}