//! Adding or fixing a segment by typing its times.
//!
//! You type clock times ("22:00", "1:30am"); the editor shows right away
//! which exact moments they mean (see `time::resolve`), so a night shift
//! "22:00 to 01:30" visibly ends the next day.

use jiff::civil::Date;
use jiff::{Timestamp, ToSpan, Zoned};
use ratatui::Frame;
use ratatui::crossterm::event::KeyEvent;
use ratatui::layout::Rect;
use ratatui::style::{Modifier, Style};
use ratatui::text::{Line, Span};
use ratatui::widgets::Paragraph;

use super::{field_line, message_line, window};
use crate::action::Action;
use crate::domain::{Segment, WorkDay};
use crate::time::format::{parse_date, parse_time};
use crate::time::resolve::{nearest, next_after};
use crate::ui::keymap::{self, Binding, Command};
use crate::ui::widgets::text_input::{InputEvent, TextInput};
use crate::ui::{Component, Context};

/// What is being edited.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Target {
    /// A new segment for the work day `day`, placed after (or before) its
    /// existing segments.
    New { day: Date, after: bool },
    /// Segment number `index` of the work day `day`.
    Existing { day: Date, index: usize, original: Segment },
    /// The session in progress. Leaving the end empty keeps it running.
    Running { day: Date, since: Timestamp },
}

pub struct SegmentEditor {
    target: Target,
    start: TextInput,
    end: TextInput,
    day: TextInput,
    /// The field with the focus: 0 = start, 1 = end, 2 = work day.
    field: usize,
    inserting: bool,
    error: Option<String>,
}

/// The typed fields, turned into exact moments.
struct Resolved {
    start: Zoned,
    end: Option<Zoned>,
    day: Date,
}

impl SegmentEditor {
    pub fn new(target: Target, ctx: &Context) -> SegmentEditor {
        let (start, end, day) = match target {
            Target::New { day, .. } => (String::new(), String::new(), day),
            Target::Existing { day, original, .. } => {
                (ctx.time(original.start()), ctx.time(original.end()), day)
            }
            Target::Running { day, since } => (ctx.time(since), String::new(), day),
        };
        SegmentEditor {
            target,
            start: TextInput::new(start),
            end: TextInput::new(end),
            day: TextInput::new(day.to_string()),
            field: 0,
            inserting: true,
            error: None,
        }
    }

    fn is_running(&self) -> bool {
        matches!(self.target, Target::Running { .. })
    }

    fn field_count(&self) -> usize {
        if self.is_running() { 2 } else { 3 }
    }

    fn input(&mut self) -> &mut TextInput {
        match self.field {
            0 => &mut self.start,
            1 => &mut self.end,
            _ => &mut self.day,
        }
    }

    /// The work day the segment is filed under (the Work day field, which
    /// also takes shortcuts like "yesterday", "-3" or "mon").
    fn work_day(&self, ctx: &Context) -> Result<Date, String> {
        match self.target {
            Target::Running { day, .. } => Ok(day),
            _ => parse_date(self.day.text(), ctx.now.date()).map_err(|error| format!("work day: {error}")),
        }
    }

    /// Where typed start times are placed: close to this moment, on the
    /// work day `day` (the one in the Work day field).
    fn reference(&self, day: Date, ctx: &Context) -> Zoned {
        match self.target {
            // Next to the day's existing work, or around noon on an empty day.
            Target::New { after, .. } => {
                let work_day = ctx.day(day);
                let edge = if after {
                    work_day.and_then(WorkDay::last_end)
                } else {
                    work_day.and_then(WorkDay::first_start)
                };
                edge.map_or_else(|| ctx.noon(day), |moment| ctx.local(moment))
            }
            // Moving a segment to another work day moves its times with it,
            // keeping the same clock times.
            Target::Existing { day: original_day, original, .. } => {
                let moved_days = day.duration_since(original_day).as_hours() / 24;
                let start = ctx.local(original.start());
                start.checked_add(moved_days.days()).unwrap_or(start)
            }
            Target::Running { since, .. } => ctx.local(since),
        }
    }

    fn resolve(&self, ctx: &Context) -> Result<Resolved, String> {
        let day = self.work_day(ctx)?;
        let start_time = parse_time(self.start.text()).map_err(|error| format!("start: {error}"))?;
        let start = nearest(start_time, &self.reference(day, ctx));
        let end = match self.end.text().trim() {
            "" if self.is_running() => None,
            "" => return Err("end: when did it end?".into()),
            text => {
                let end_time = parse_time(text).map_err(|error| format!("end: {error}"))?;
                Some(next_after(end_time, &start))
            }
        };
        Ok(Resolved { start, end, day })
    }

    fn submit(&mut self, ctx: &Context) -> Option<Action> {
        let result = self.resolve(ctx).and_then(|resolved| self.action(resolved));
        match result {
            Ok(action) => Some(action),
            Err(error) => {
                self.error = Some(error);
                None
            }
        }
    }

    fn action(&self, resolved: Resolved) -> Result<Action, String> {
        let start = resolved.start.timestamp();
        let end = resolved.end.map(|end| end.timestamp());
        if let Target::Running { .. } = self.target {
            return Ok(Action::FixRunning { since: start, stopped: end });
        }
        let segment =
            Segment::new(start, end.ok_or("end: when did it end?")?).map_err(|error| error.to_string())?;
        Ok(match self.target {
            Target::Existing { day, index, .. } => {
                Action::ReplaceSegment { day, index, segment, new_day: resolved.day }
            }
            _ => Action::AddSegment { day: resolved.day, segment },
        })
    }

    fn title(&self, ctx: &Context) -> String {
        match self.target {
            Target::New { day, .. } => format!("Add work · {}", ctx.fmt.date_short(day)),
            Target::Existing { day, index, .. } => {
                format!("Segment {} · {}", index + 1, ctx.fmt.date_short(day))
            }
            Target::Running { .. } => "The session in progress".to_string(),
        }
    }

    /// The exact moment a field means, next to it.
    fn note(moment: Option<&Zoned>, empty_note: &str, ctx: &Context) -> Span<'static> {
        match moment {
            Some(moment) => Span::styled(
                format!("{} {}", ctx.fmt.date_short(moment.date()), ctx.fmt.time(moment.time())),
                ctx.theme.accent(),
            ),
            None => Span::styled(empty_note.to_string(), ctx.theme.muted()),
        }
    }
}

impl Component for SegmentEditor {
    fn keys(&self) -> &'static [&'static [Binding]] {
        &[keymap::POPUP]
    }

    fn render(&mut self, frame: &mut Frame, area: Rect, ctx: &Context) {
        let title = self.title(ctx);
        let inner =
            window(frame, area, 76, 11, &title, "Enter save · Tab next field · Esc cancel", ctx.theme);
        let resolved = self.resolve(ctx);
        let (start, end) = match &resolved {
            Ok(resolved) => (Some(&resolved.start), resolved.end.as_ref()),
            Err(_) => (None, None),
        };
        let end_note = if self.is_running() { "empty = still working" } else { "" };

        let mut lines = vec![
            Line::default(),
            field_line(
                "Start",
                &self.start,
                self.field == 0,
                self.inserting,
                Self::note(start, "", ctx),
                ctx.theme,
            ),
            field_line(
                "End",
                &self.end,
                self.field == 1,
                self.inserting,
                Self::note(end, end_note, ctx),
                ctx.theme,
            ),
        ];
        if !self.is_running() {
            // Which date the field means ("yesterday" → Wed Sep 23).
            let note = match self.work_day(ctx) {
                Ok(day) => Span::styled(ctx.fmt.date_short(day), ctx.theme.accent()),
                Err(_) => Span::styled("a date, yesterday, -3, mon...", ctx.theme.muted()),
            };
            lines.push(field_line("Work day", &self.day, self.field == 2, self.inserting, note, ctx.theme));
        }
        lines.push(Line::default());
        let length = match (start, end) {
            (Some(start), Some(end)) => ctx.fmt.duration(end.duration_since(start)),
            (Some(start), None) if self.is_running() => {
                ctx.fmt.duration(ctx.now.duration_since(start)) + " so far"
            }
            _ => String::new(),
        };
        lines.push(Line::from(vec![
            Span::raw("  Length    "),
            Span::styled(length, Style::new().add_modifier(Modifier::BOLD)),
        ]));
        let tip = "22:30, 2230 or 10:30pm all work. An end before the start is the next day.";
        lines.push(message_line(self.error.as_deref(), tip, ctx.theme));
        frame.render_widget(Paragraph::new(lines), inner);
    }

    fn command(&mut self, command: Command, _count: Option<usize>, ctx: &Context) -> Option<Action> {
        match command {
            Command::Confirm => return self.submit(ctx),
            Command::Close => return Some(Action::ClosePopup),
            Command::Down => self.field = (self.field + 1) % self.field_count(),
            Command::Up => self.field = (self.field + self.field_count() - 1) % self.field_count(),
            Command::Top => self.field = 0,
            Command::Bottom => self.field = self.field_count() - 1,
            Command::Insert => {
                self.input().cursor_to_end();
                self.inserting = true;
            }
            Command::InsertAtStart => {
                self.input().cursor_to_start();
                self.inserting = true;
            }
            Command::Retype => {
                self.input().clear();
                self.inserting = true;
            }
            _ => {}
        }
        None
    }

    fn inserting(&self) -> bool {
        self.inserting
    }

    fn insert_key(&mut self, key: KeyEvent, ctx: &Context) -> Option<Action> {
        self.error = None;
        match self.input().insert_key(key) {
            InputEvent::Submit => return self.submit(ctx),
            InputEvent::Exit => self.inserting = false,
            InputEvent::Next => self.field = (self.field + 1) % self.field_count(),
            InputEvent::Previous => self.field = (self.field + self.field_count() - 1) % self.field_count(),
            InputEvent::Edited => {}
        }
        None
    }
}