use std::cmp;

use chrono::{Datelike, NaiveDate};

use crate::files::primitives::{Time, Weekday};

use super::layout::line::{LineEntry, LineLayout, SpanSegment};

struct ShowLines {
    num_width: usize,
    span_width: usize,
    result: String,
}

impl ShowLines {
    fn new(num_width: usize, span_width: usize) -> Self {
        Self {
            num_width,
            span_width,
            result: String::new(),
        }
    }

    fn display_line(&mut self, line: &LineEntry) {
        match line {
            LineEntry::Day { spans, date } => self.display_line_date(spans, *date),
            LineEntry::Now { spans, time } => self.display_line_now(spans, *time),
            LineEntry::Entry {
                number,
                spans,
                time,
                text,
            } => self.display_line_entry(*number, spans, *time, text),
        }
    }

    fn display_line_date(&mut self, spans: &[Option<SpanSegment>], date: NaiveDate) {
        let weekday: Weekday = date.weekday().into();
        let weekday = weekday.full_name();
        self.push(&format!(
            "{:=>nw$}={:=<sw$}===  {:9}  {}  ==={:=<sw$}={:=>nw$}\n",
            "",
            Self::display_spans(spans, '='),
            weekday,
            date,
            "",
            "",
            nw = self.num_width,
            sw = self.span_width
        ));
    }

    fn display_line_now(&mut self, spans: &[Option<SpanSegment>], time: Time) {
        self.push(&format!(
            "{:<nw$} {:sw$} {}\n",
            "now",
            Self::display_spans(spans, ' '),
            time,
            nw = self.num_width,
            sw = self.span_width
        ));
    }

    fn display_line_entry(
        &mut self,
        number: Option<usize>,
        spans: &[Option<SpanSegment>],
        time: Option<Time>,
        text: &str,
    ) {
        let num = match number {
            Some(n) => format!("{}", n),
            None => "".to_string(),
        };

        let time = match time {
            Some(t) => format!("{} ", t),
            None => "".to_string(),
        };

        self.push(&format!(
            "{:>nw$} {:sw$} {}{}\n",
            num,
            Self::display_spans(spans, ' '),
            time,
            text,
            nw = self.num_width,
            sw = self.span_width
        ))
    }

    fn display_spans(spans: &[Option<SpanSegment>], empty: char) -> String {
        let mut result = String::new();
        for segment in spans {
            result.push(match segment {
                Some(SpanSegment::Start) => '┌',
                Some(SpanSegment::Middle) => '│',
                Some(SpanSegment::End) => '└',
                None => empty,
            });
        }
        result
    }

    fn push(&mut self, line: &str) {
        self.result.push_str(line);
    }

    fn result(self) -> String {
        self.result
    }
}

pub fn show_all(layout: &LineLayout) -> String {
    let num_width = cmp::max(layout.num_width(), 3); // `now` is 3 chars wide
    let mut show_lines = ShowLines::new(num_width, layout.span_width());
    for line in layout.lines() {
        show_lines.display_line(line);
    }
    show_lines.result()
}