use helix_core::diagnostic::Severity;
use helix_core::doc_formatter::{FormattedGrapheme, TextFormat};
use helix_core::text_annotations::LineAnnotation;
use helix_core::{softwrapped_dimensions, Diagnostic, Position};
use serde::{Deserialize, Serialize};

use crate::Document;

/// Describes the severity level of a [`Diagnostic`].
#[derive(Debug, Clone, Copy, Eq, PartialEq, PartialOrd, Ord)]
pub enum DiagnosticFilter {
    Disable,
    Enable(Severity),
}

impl<'de> Deserialize<'de> for DiagnosticFilter {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        match &*String::deserialize(deserializer)? {
            "disable" => Ok(DiagnosticFilter::Disable),
            "hint" => Ok(DiagnosticFilter::Enable(Severity::Hint)),
            "info" => Ok(DiagnosticFilter::Enable(Severity::Info)),
            "warning" => Ok(DiagnosticFilter::Enable(Severity::Warning)),
            "error" => Ok(DiagnosticFilter::Enable(Severity::Error)),
            variant => Err(serde::de::Error::unknown_variant(
                variant,
                &["disable", "hint", "info", "warning", "error"],
            )),
        }
    }
}

impl Serialize for DiagnosticFilter {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        let filter = match self {
            DiagnosticFilter::Disable => "disable",
            DiagnosticFilter::Enable(Severity::Hint) => "hint",
            DiagnosticFilter::Enable(Severity::Info) => "info",
            DiagnosticFilter::Enable(Severity::Warning) => "warning",
            DiagnosticFilter::Enable(Severity::Error) => "error",
        };
        filter.serialize(serializer)
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(default, rename_all = "kebab-case", deny_unknown_fields)]
pub struct InlineDiagnosticsConfig {
    pub cursor_line: DiagnosticFilter,
    pub other_lines: DiagnosticFilter,
    pub min_diagnostic_width: u16,
    pub prefix_len: u16,
    pub max_wrap: u16,
    pub max_diagnostics: usize,
}

impl InlineDiagnosticsConfig {
    pub fn disabled(&self) -> bool {
        matches!(
            self,
            Self {
                cursor_line: DiagnosticFilter::Disable,
                other_lines: DiagnosticFilter::Disable,
                ..
            }
        )
    }

    pub fn prepare(&self, width: u16, enable_cursor_line: bool) -> Self {
        let mut config = self.clone();
        if width < self.min_diagnostic_width + self.prefix_len {
            config.cursor_line = DiagnosticFilter::Disable;
            config.other_lines = DiagnosticFilter::Disable;
        } else if !enable_cursor_line {
            config.cursor_line = self.cursor_line.min(self.other_lines);
        }
        config
    }

    pub fn max_diagnostic_start(&self, width: u16) -> u16 {
        width - self.min_diagnostic_width - self.prefix_len
    }

    pub fn text_fmt(&self, anchor_col: u16, width: u16) -> TextFormat {
        let width = if anchor_col > self.max_diagnostic_start(width) {
            self.min_diagnostic_width
        } else {
            width - anchor_col - self.prefix_len
        };

        TextFormat {
            soft_wrap: true,
            tab_width: 4,
            max_wrap: self.max_wrap.min(width / 4),
            max_indent_retain: 0,
            wrap_indicator: "".into(),
            wrap_indicator_highlight: None,
            viewport_width: width,
            soft_wrap_at_text_width: true,
        }
    }
}

impl Default for InlineDiagnosticsConfig {
    fn default() -> Self {
        InlineDiagnosticsConfig {
            cursor_line: DiagnosticFilter::Disable,
            other_lines: DiagnosticFilter::Disable,
            min_diagnostic_width: 40,
            prefix_len: 1,
            max_wrap: 20,
            max_diagnostics: 10,
        }
    }
}

pub struct InlineDiagnosticAccumulator<'a> {
    idx: usize,
    doc: &'a Document,
    pub stack: Vec<(&'a Diagnostic, u16)>,
    pub config: InlineDiagnosticsConfig,
    cursor: usize,
    cursor_line: bool,
}

impl<'a> InlineDiagnosticAccumulator<'a> {
    pub fn new(cursor: usize, doc: &'a Document, config: InlineDiagnosticsConfig) -> Self {
        InlineDiagnosticAccumulator {
            idx: 0,
            doc,
            stack: Vec::new(),
            config,
            cursor,
            cursor_line: false,
        }
    }

    pub fn reset_pos(&mut self, char_idx: usize) -> usize {
        self.idx = 0;
        self.clear();
        self.skip_concealed(char_idx)
    }

    pub fn skip_concealed(&mut self, conceal_end_char_idx: usize) -> usize {
        let diagnostics = &self.doc.diagnostics[self.idx..];
        let idx = diagnostics.partition_point(|diag| diag.range.start < conceal_end_char_idx);
        self.idx += idx;
        self.next_anchor(conceal_end_char_idx)
    }

    pub fn next_anchor(&self, current_char_idx: usize) -> usize {
        let next_diag_start = self
            .doc
            .diagnostics
            .get(self.idx)
            .map_or(usize::MAX, |diag| diag.range.start);
        if (current_char_idx..next_diag_start).contains(&self.cursor) {
            self.cursor
        } else {
            next_diag_start
        }
    }

    pub fn clear(&mut self) {
        self.cursor_line = false;
        self.stack.clear();
    }

    fn process_anchor_impl(
        &mut self,
        grapheme: &FormattedGrapheme,
        width: u16,
        horizontal_off: usize,
    ) -> bool {
        // TODO: doing the cursor tracking here works well but is somewhat
        // duplicate effort/tedious maybe centralize this somewhere?
        // In the DocFormatter?
        if grapheme.char_idx == self.cursor {
            self.cursor_line = true;
            if self
                .doc
                .diagnostics
                .get(self.idx)
                .map_or(true, |diag| diag.range.start != grapheme.char_idx)
            {
                return false;
            }
        }

        let Some(anchor_col) = grapheme.visual_pos.col.checked_sub(horizontal_off) else {
            return true;
        };
        if anchor_col >= width as usize {
            return true;
        }

        for diag in &self.doc.diagnostics[self.idx..] {
            if diag.range.start != grapheme.char_idx {
                break;
            }
            self.stack.push((diag, anchor_col as u16));
            self.idx += 1;
        }
        false
    }

    pub fn proccess_anchor(
        &mut self,
        grapheme: &FormattedGrapheme,
        width: u16,
        horizontal_off: usize,
    ) -> usize {
        if self.process_anchor_impl(grapheme, width, horizontal_off) {
            self.idx += self.doc.diagnostics[self.idx..]
                .iter()
                .take_while(|diag| diag.range.start == grapheme.char_idx)
                .count();
        }
        self.next_anchor(grapheme.char_idx + 1)
    }

    pub fn filter(&self) -> DiagnosticFilter {
        if self.cursor_line {
            self.config.cursor_line
        } else {
            self.config.other_lines
        }
    }

    pub fn compute_line_diagnostics(&mut self) {
        let filter = if self.cursor_line {
            self.cursor_line = false;
            self.config.cursor_line
        } else {
            self.config.other_lines
        };
        let DiagnosticFilter::Enable(filter) = filter else {
            self.stack.clear();
            return;
        };
        self.stack.retain(|(diag, _)| diag.severity() >= filter);
        self.stack.truncate(self.config.max_diagnostics)
    }

    pub fn has_multi(&self, width: u16) -> bool {
        self.stack
            .last()
            .is_some_and(|&(_, anchor)| anchor > self.config.max_diagnostic_start(width))
    }
}

pub(crate) struct InlineDiagnostics<'a> {
    state: InlineDiagnosticAccumulator<'a>,
    width: u16,
    horizontal_off: usize,
}

impl<'a> InlineDiagnostics<'a> {
    #[allow(clippy::new_ret_no_self)]
    pub(crate) fn new(
        doc: &'a Document,
        cursor: usize,
        width: u16,
        horizontal_off: usize,
        config: InlineDiagnosticsConfig,
    ) -> Box<dyn LineAnnotation + 'a> {
        Box::new(InlineDiagnostics {
            state: InlineDiagnosticAccumulator::new(cursor, doc, config),
            width,
            horizontal_off,
        })
    }
}

impl LineAnnotation for InlineDiagnostics<'_> {
    fn reset_pos(&mut self, char_idx: usize) -> usize {
        self.state.reset_pos(char_idx)
    }

    fn skip_concealed_anchors(&mut self, conceal_end_char_idx: usize) -> usize {
        self.state.skip_concealed(conceal_end_char_idx)
    }

    fn process_anchor(&mut self, grapheme: &FormattedGrapheme) -> usize {
        self.state
            .proccess_anchor(grapheme, self.width, self.horizontal_off)
    }

    fn insert_virtual_lines(
        &mut self,
        _line_end_char_idx: usize,
        _line_end_visual_pos: Position,
        _doc_line: usize,
    ) -> Position {
        self.state.compute_line_diagnostics();
        let multi = self.state.has_multi(self.width);
        let diagostic_height: usize = self
            .state
            .stack
            .drain(..)
            .map(|(diag, anchor)| {
                let text_fmt = self.state.config.text_fmt(anchor, self.width);
                softwrapped_dimensions(diag.message.as_str().trim().into(), &text_fmt).0
            })
            .sum();
        Position::new(multi as usize + diagostic_height, 0)
    }
}