//! # Convert from SCSS AST to CSS
use std::io::Write;

use codemap::CodeMap;

use crate::{
    atrule::{
        keyframes::{Keyframes, KeyframesRuleSet, KeyframesSelector},
        media::MediaRule,
        SupportsRule, UnknownAtRule,
    },
    error::SassResult,
    parse::Stmt,
    selector::Selector,
    style::Style,
};

#[derive(Debug, Clone)]
struct ToplevelUnknownAtRule {
    name: String,
    params: String,
    body: Vec<Stmt>,
}

#[derive(Debug, Clone)]
enum Toplevel {
    RuleSet(Selector, Vec<BlockEntry>),
    MultilineComment(String),
    UnknownAtRule(Box<ToplevelUnknownAtRule>),
    Keyframes(Box<Keyframes>),
    KeyframesRuleSet(Vec<KeyframesSelector>, Vec<BlockEntry>),
    Media { query: String, body: Vec<Stmt> },
    Supports { params: String, body: Vec<Stmt> },
    Newline,
    // todo: do we actually need a toplevel style variant?
    Style(Style),
    Import(String),
}

#[derive(Debug, Clone)]
enum BlockEntry {
    Style(Style),
    MultilineComment(String),
    Import(String),
}

impl BlockEntry {
    pub fn to_string(&self) -> SassResult<String> {
        match self {
            BlockEntry::Style(s) => s.to_string(),
            BlockEntry::MultilineComment(s) => Ok(format!("/*{}*/", s)),
            BlockEntry::Import(s) => Ok(format!("@import {};", s)),
        }
    }
}

impl Toplevel {
    const fn new_rule(selector: Selector) -> Self {
        Toplevel::RuleSet(selector, Vec::new())
    }

    fn new_keyframes_rule(selector: Vec<KeyframesSelector>) -> Self {
        Toplevel::KeyframesRuleSet(selector, Vec::new())
    }

    fn push_style(&mut self, s: Style) {
        if s.value.is_null() {
            return;
        }
        if let Toplevel::RuleSet(_, entries) | Toplevel::KeyframesRuleSet(_, entries) = self {
            entries.push(BlockEntry::Style(s));
        } else {
            panic!()
        }
    }

    fn push_comment(&mut self, s: String) {
        if let Toplevel::RuleSet(_, entries) | Toplevel::KeyframesRuleSet(_, entries) = self {
            entries.push(BlockEntry::MultilineComment(s));
        } else {
            panic!()
        }
    }

    fn push_import(&mut self, s: String) {
        if let Toplevel::RuleSet(_, entries) | Toplevel::KeyframesRuleSet(_, entries) = self {
            entries.push(BlockEntry::Import(s));
        } else {
            panic!()
        }
    }
}

#[derive(Debug, Clone)]
pub(crate) struct Css {
    blocks: Vec<Toplevel>,
    in_at_rule: bool,
    allows_charset: bool,
}

impl Css {
    pub const fn new(in_at_rule: bool, allows_charset: bool) -> Self {
        Css {
            blocks: Vec::new(),
            in_at_rule,
            allows_charset,
        }
    }

    pub(crate) fn from_stmts(
        s: Vec<Stmt>,
        in_at_rule: bool,
        allows_charset: bool,
    ) -> SassResult<Self> {
        Css::new(in_at_rule, allows_charset).parse_stylesheet(s)
    }

    fn parse_stmt(&mut self, stmt: Stmt) -> SassResult<Vec<Toplevel>> {
        Ok(match stmt {
            Stmt::RuleSet { selector, body } => {
                if body.is_empty() {
                    return Ok(Vec::new());
                }
                let selector = selector.into_selector().remove_placeholders();
                if selector.is_empty() {
                    return Ok(Vec::new());
                }
                let mut vals = vec![Toplevel::new_rule(selector)];
                for rule in body {
                    match rule {
                        Stmt::RuleSet { .. } => vals.extend(self.parse_stmt(rule)?),
                        Stmt::Style(s) => vals.first_mut().unwrap().push_style(s),
                        Stmt::Comment(s) => vals.first_mut().unwrap().push_comment(s),
                        Stmt::Media(m) => {
                            let MediaRule { query, body, .. } = *m;
                            vals.push(Toplevel::Media { query, body })
                        }
                        Stmt::Supports(s) => {
                            let SupportsRule { params, body } = *s;
                            vals.push(Toplevel::Supports { params, body })
                        }
                        Stmt::UnknownAtRule(u) => {
                            let UnknownAtRule {
                                params, body, name, ..
                            } = *u;
                            vals.push(Toplevel::UnknownAtRule(Box::new(ToplevelUnknownAtRule {
                                params,
                                body,
                                name,
                            })))
                        }
                        Stmt::Return(..) => unreachable!(),
                        Stmt::AtRoot { body } => {
                            body.into_iter().try_for_each(|r| -> SassResult<()> {
                                vals.append(&mut self.parse_stmt(r)?);
                                Ok(())
                            })?
                        }
                        Stmt::Keyframes(k) => {
                            let Keyframes { rule, name, body } = *k;
                            vals.push(Toplevel::Keyframes(Box::new(Keyframes {
                                rule,
                                name,
                                body,
                            })))
                        }
                        k @ Stmt::KeyframesRuleSet(..) => {
                            unreachable!("@keyframes ruleset {:?}", k)
                        }
                        Stmt::Import(s) => vals.first_mut().unwrap().push_import(s),
                    };
                }
                vals
            }
            Stmt::Comment(s) => vec![Toplevel::MultilineComment(s)],
            Stmt::Import(s) => vec![Toplevel::Import(s)],
            Stmt::Style(s) => vec![Toplevel::Style(s)],
            Stmt::Media(m) => {
                let MediaRule { query, body, .. } = *m;
                vec![Toplevel::Media { query, body }]
            }
            Stmt::Supports(s) => {
                let SupportsRule { params, body } = *s;
                vec![Toplevel::Supports { params, body }]
            }
            Stmt::UnknownAtRule(u) => {
                let UnknownAtRule {
                    params, body, name, ..
                } = *u;
                vec![Toplevel::UnknownAtRule(Box::new(ToplevelUnknownAtRule {
                    params,
                    name,
                    body,
                }))]
            }
            Stmt::Return(..) => unreachable!("@return: {:?}", stmt),
            Stmt::AtRoot { .. } => unreachable!("@at-root: {:?}", stmt),
            Stmt::Keyframes(k) => vec![Toplevel::Keyframes(k)],
            Stmt::KeyframesRuleSet(k) => {
                let KeyframesRuleSet { body, selector } = *k;
                if body.is_empty() {
                    return Ok(Vec::new());
                }
                let mut vals = vec![Toplevel::new_keyframes_rule(selector)];
                for rule in body {
                    match rule {
                        Stmt::Style(s) => vals.first_mut().unwrap().push_style(s),
                        Stmt::KeyframesRuleSet(..) => vals.extend(self.parse_stmt(rule)?),
                        _ => todo!(),
                    }
                }
                vals
            }
        })
    }

    fn parse_stylesheet(mut self, stmts: Vec<Stmt>) -> SassResult<Css> {
        let mut is_first = true;
        for stmt in stmts {
            let v = self.parse_stmt(stmt)?;
            // this is how we print newlines between unrelated styles
            // it could probably be refactored
            if !v.is_empty() {
                if let Some(Toplevel::MultilineComment(..)) = v.first() {
                } else if is_first {
                    is_first = false;
                } else {
                    self.blocks.push(Toplevel::Newline);
                }
                self.blocks.extend(v);
            }
        }
        Ok(self)
    }

    pub fn pretty_print(self, map: &CodeMap) -> SassResult<String> {
        let mut string = Vec::new();
        let allows_charset = self.allows_charset;
        self._inner_pretty_print(&mut string, map, 0)?;
        if allows_charset && string.iter().any(|s| !s.is_ascii()) {
            return Ok(format!("@charset \"UTF-8\";\n{}", unsafe {
                String::from_utf8_unchecked(string)
            }));
        }
        Ok(unsafe { String::from_utf8_unchecked(string) })
    }

    fn _inner_pretty_print(
        self,
        buf: &mut Vec<u8>,
        map: &CodeMap,
        nesting: usize,
    ) -> SassResult<()> {
        let mut has_written = false;
        let padding = vec![' '; nesting * 2].iter().collect::<String>();
        let mut should_emit_newline = false;
        for block in self.blocks {
            match block {
                Toplevel::RuleSet(selector, styles) => {
                    if styles.is_empty() {
                        continue;
                    }
                    has_written = true;
                    if should_emit_newline && !self.in_at_rule {
                        should_emit_newline = false;
                        writeln!(buf)?;
                    }
                    writeln!(buf, "{}{} {{", padding, selector)?;
                    for style in styles {
                        writeln!(buf, "{}  {}", padding, style.to_string()?)?;
                    }
                    writeln!(buf, "{}}}", padding)?;
                }
                Toplevel::KeyframesRuleSet(selector, body) => {
                    if body.is_empty() {
                        continue;
                    }
                    has_written = true;

                    writeln!(
                        buf,
                        "{}{} {{",
                        padding,
                        selector
                            .into_iter()
                            .map(|s| s.to_string())
                            .collect::<Vec<String>>()
                            .join(", ")
                    )?;
                    for style in body {
                        writeln!(buf, "{}  {}", padding, style.to_string()?)?;
                    }
                    writeln!(buf, "{}}}", padding)?;
                }
                Toplevel::MultilineComment(s) => {
                    has_written = true;
                    writeln!(buf, "{}/*{}*/", padding, s)?;
                }
                Toplevel::Import(s) => {
                    has_written = true;
                    writeln!(buf, "{}@import {};", padding, s)?;
                }
                Toplevel::UnknownAtRule(u) => {
                    let ToplevelUnknownAtRule { params, name, body } = *u;
                    if should_emit_newline {
                        should_emit_newline = false;
                        writeln!(buf)?;
                    }

                    if params.is_empty() {
                        write!(buf, "{}@{}", padding, name)?;
                    } else {
                        write!(buf, "{}@{} {}", padding, name, params)?;
                    }

                    if body.is_empty() {
                        writeln!(buf, ";")?;
                        continue;
                    } else {
                        writeln!(buf, " {{")?;
                    }

                    Css::from_stmts(body, true, self.allows_charset)?._inner_pretty_print(
                        buf,
                        map,
                        nesting + 1,
                    )?;
                    writeln!(buf, "{}}}", padding)?;
                }
                Toplevel::Keyframes(k) => {
                    let Keyframes { rule, name, body } = *k;
                    if should_emit_newline {
                        should_emit_newline = false;
                        writeln!(buf)?;
                    }

                    write!(buf, "{}@{}", padding, rule)?;

                    if !name.is_empty() {
                        write!(buf, " {}", name)?;
                    }

                    if body.is_empty() {
                        writeln!(buf, " {{}}")?;
                        continue;
                    } else {
                        writeln!(buf, " {{")?;
                    }

                    Css::from_stmts(body, true, self.allows_charset)?._inner_pretty_print(
                        buf,
                        map,
                        nesting + 1,
                    )?;
                    writeln!(buf, "{}}}", padding)?;
                }
                Toplevel::Supports { params, body } => {
                    if should_emit_newline {
                        should_emit_newline = false;
                        writeln!(buf)?;
                    }

                    if params.is_empty() {
                        write!(buf, "{}@supports", padding)?;
                    } else {
                        write!(buf, "{}@supports {}", padding, params)?;
                    }

                    if body.is_empty() {
                        writeln!(buf, ";")?;
                        continue;
                    } else {
                        writeln!(buf, " {{")?;
                    }

                    Css::from_stmts(body, true, self.allows_charset)?._inner_pretty_print(
                        buf,
                        map,
                        nesting + 1,
                    )?;
                    writeln!(buf, "{}}}", padding)?;
                }
                Toplevel::Media { query, body } => {
                    if body.is_empty() {
                        continue;
                    }

                    writeln!(buf, "{}@media {} {{", padding, query)?;
                    Css::from_stmts(body, true, self.allows_charset)?._inner_pretty_print(
                        buf,
                        map,
                        nesting + 1,
                    )?;
                    writeln!(buf, "{}}}", padding)?;
                }
                Toplevel::Style(s) => {
                    writeln!(buf, "{}{}", padding, s.to_string()?)?;
                }
                Toplevel::Newline => {
                    if has_written {
                        should_emit_newline = true;
                    }
                    continue;
                }
            }
        }
        Ok(())
    }
}