use std::time::Instant;

use ratatui::layout::{Alignment, Constraint, Layout, Rect};
use ratatui::style::{Color, Modifier, Style};
use ratatui::text::{Line, Span};
use ratatui::widgets::{Block, Borders, Paragraph};
use ratatui::Frame;

use crate::app::App;
use crate::engine::{LinkState, SequencerSnapshot};
use crate::model::SourceSpan;
use crate::page::Page;
use crate::state::{FlashKind, Modal, PanelFocus, PatternField, SidePanel};
use crate::views::highlight::{self, highlight_line, highlight_line_with_runtime};
use crate::widgets::{ConfirmModal, ModalFrame, NavMinimap, NavTile, SampleBrowser, TextInputModal};

use super::{dict_view, engine_view, help_view, main_view, options_view, patterns_view, title_view};

fn adjust_spans_for_line(spans: &[SourceSpan], line_start: usize, line_len: usize) -> Vec<SourceSpan> {
    spans.iter().filter_map(|s| {
        if s.end <= line_start || s.start >= line_start + line_len {
            return None;
        }
        Some(SourceSpan {
            start: s.start.max(line_start) - line_start,
            end: (s.end.min(line_start + line_len)) - line_start,
        })
    }).collect()
}

pub fn render(frame: &mut Frame, app: &mut App, link: &LinkState, snapshot: &SequencerSnapshot) {
    let term = frame.area();
    let blank = " ".repeat(term.width as usize);
    let lines: Vec<Line> = (0..term.height).map(|_| Line::raw(&blank)).collect();
    frame.render_widget(Paragraph::new(lines), term);

    if app.ui.show_title {
        title_view::render(frame, term, &mut app.ui);
        return;
    }

    let padded = Rect {
        x: term.x + 4,
        y: term.y + 1,
        width: term.width.saturating_sub(8),
        height: term.height.saturating_sub(2),
    };

    let [header_area, _padding, body_area, _bottom_padding, footer_area] = Layout::vertical([
        Constraint::Length(1),
        Constraint::Length(1),
        Constraint::Fill(1),
        Constraint::Length(1),
        Constraint::Length(3),
    ])
    .areas(padded);

    render_header(frame, app, link, snapshot, header_area);

    let (page_area, panel_area) = if app.panel.visible && app.panel.side.is_some() {
        if body_area.width >= 120 {
            let panel_width = body_area.width * 35 / 100;
            let [main, side] = Layout::horizontal([
                Constraint::Fill(1),
                Constraint::Length(panel_width),
            ])
            .areas(body_area);
            (main, Some(side))
        } else {
            let panel_height = body_area.height * 40 / 100;
            let [main, side] = Layout::vertical([
                Constraint::Fill(1),
                Constraint::Length(panel_height),
            ])
            .areas(body_area);
            (main, Some(side))
        }
    } else {
        (body_area, None)
    };

    match app.page {
        Page::Main => main_view::render(frame, app, snapshot, page_area),
        Page::Patterns => patterns_view::render(frame, app, snapshot, page_area),
        Page::Engine => engine_view::render(frame, app, page_area),
        Page::Options => options_view::render(frame, app, link, page_area),
        Page::Help => help_view::render(frame, app, page_area),
        Page::Dict => dict_view::render(frame, app, page_area),
    }

    if let Some(side_area) = panel_area {
        render_side_panel(frame, app, side_area);
    }

    render_footer(frame, app, footer_area);
    render_modal(frame, app, snapshot, term);

    let show_minimap = app
        .ui
        .minimap_until
        .map(|until| Instant::now() < until)
        .unwrap_or(false);

    if show_minimap {
        let tiles: Vec<NavTile> = Page::ALL
            .iter()
            .map(|p| {
                let (col, row) = p.grid_pos();
                NavTile { col, row, name: p.name() }
            })
            .collect();
        let selected = app.page.grid_pos();
        NavMinimap::new(&tiles, selected).render_centered(frame, term);
    }
}

fn render_side_panel(frame: &mut Frame, app: &App, area: Rect) {
    let focused = app.panel.focus == PanelFocus::Side;
    match &app.panel.side {
        Some(SidePanel::SampleBrowser(state)) => {
            let entries = state.entries();
            SampleBrowser::new(&entries, state.cursor)
                .scroll_offset(state.scroll_offset)
                .search(&state.search_query, state.search_active)
                .focused(focused)
                .render(frame, area);
        }
        None => {}
    }
}

fn render_header(
    frame: &mut Frame,
    app: &App,
    link: &LinkState,
    snapshot: &SequencerSnapshot,
    area: Rect,
) {
    use crate::model::PatternSpeed;

    let bank = &app.project_state.project.banks[app.editor_ctx.bank];
    let pattern = &bank.patterns[app.editor_ctx.pattern];

    // Layout: [Transport] [Live] [Tempo] [Bank] [Pattern] [Stats]
    let [transport_area, live_area, tempo_area, bank_area, pattern_area, stats_area] =
        Layout::horizontal([
            Constraint::Min(12),
            Constraint::Length(9),
            Constraint::Min(14),
            Constraint::Fill(1),
            Constraint::Fill(2),
            Constraint::Min(20),
        ])
        .areas(area);

    // Transport block
    let (transport_bg, transport_text) = if app.playback.playing {
        (Color::Rgb(30, 80, 30), " ▶ PLAYING ")
    } else {
        (Color::Rgb(80, 30, 30), " ■ STOPPED ")
    };
    let transport_style = Style::new().bg(transport_bg).fg(Color::White);
    frame.render_widget(
        Paragraph::new(transport_text)
            .style(transport_style)
            .alignment(Alignment::Center),
        transport_area,
    );

    // Fill indicator
    let fill = app.live_keys.fill();
    let fill_style = if fill {
        Style::new().bg(Color::Rgb(30, 30, 35)).fg(Color::Rgb(100, 220, 100))
    } else {
        Style::new().bg(Color::Rgb(30, 30, 35)).fg(Color::Rgb(60, 60, 70))
    };
    frame.render_widget(
        Paragraph::new(if fill { "F" } else { "·" })
            .style(fill_style)
            .alignment(Alignment::Center),
        live_area,
    );

    // Tempo block
    let tempo_style = Style::new()
        .bg(Color::Rgb(60, 30, 60))
        .fg(Color::White)
        .add_modifier(Modifier::BOLD);
    frame.render_widget(
        Paragraph::new(format!(" {:.1} BPM ", link.tempo()))
            .style(tempo_style)
            .alignment(Alignment::Center),
        tempo_area,
    );

    // Bank block
    let bank_name = bank
        .name
        .as_deref()
        .map(|n| format!(" {n} "))
        .unwrap_or_else(|| format!(" Bank {:02} ", app.editor_ctx.bank + 1));
    let bank_style = Style::new().bg(Color::Rgb(30, 60, 70)).fg(Color::White);
    frame.render_widget(
        Paragraph::new(bank_name)
            .style(bank_style)
            .alignment(Alignment::Center),
        bank_area,
    );

    // Pattern block (name + length + speed + page + iter)
    let default_pattern_name = format!("Pattern {:02}", app.editor_ctx.pattern + 1);
    let pattern_name = pattern.name.as_deref().unwrap_or(&default_pattern_name);
    let speed_info = if pattern.speed != PatternSpeed::Normal {
        format!(" · {}", pattern.speed.label())
    } else {
        String::new()
    };
    let total_pages = pattern.length.div_ceil(32);
    let page_info = if total_pages > 1 {
        let current_page = app.editor_ctx.step / 32 + 1;
        format!(" · {current_page}/{total_pages}")
    } else {
        String::new()
    };
    let iter_info = snapshot
        .get_iter(app.editor_ctx.bank, app.editor_ctx.pattern)
        .map(|iter| format!(" · #{}", iter + 1))
        .unwrap_or_default();
    let pattern_text = format!(
        " {} · {} steps{}{}{} ",
        pattern_name, pattern.length, speed_info, page_info, iter_info
    );
    let pattern_style = Style::new().bg(Color::Rgb(30, 50, 50)).fg(Color::White);
    frame.render_widget(
        Paragraph::new(pattern_text)
            .style(pattern_style)
            .alignment(Alignment::Center),
        pattern_area,
    );

    // Stats block
    let cpu_pct = (app.metrics.cpu_load * 100.0).min(100.0);
    let peers = link.peers();
    let voices = app.metrics.active_voices;
    let stats_text = format!(" CPU {cpu_pct:.0}%  V:{voices}  L:{peers} ");
    let stats_style = Style::new()
        .bg(Color::Rgb(35, 35, 40))
        .fg(Color::Rgb(150, 150, 160));
    frame.render_widget(
        Paragraph::new(stats_text)
            .style(stats_style)
            .alignment(Alignment::Right),
        stats_area,
    );
}

fn render_footer(frame: &mut Frame, app: &App, area: Rect) {
    let block = Block::default().borders(Borders::ALL);
    let inner = block.inner(area);
    let available_width = inner.width as usize;

    let page_indicator = match app.page {
        Page::Main => "[MAIN]",
        Page::Patterns => "[PATTERNS]",
        Page::Engine => "[ENGINE]",
        Page::Options => "[OPTIONS]",
        Page::Help => "[HELP]",
        Page::Dict => "[DICT]",
    };

    let content = if let Some(ref msg) = app.ui.status_message {
        Line::from(vec![
            Span::styled(
                page_indicator.to_string(),
                Style::new().fg(Color::White).add_modifier(Modifier::DIM),
            ),
            Span::raw("  "),
            Span::styled(msg.clone(), Style::new().fg(Color::Yellow)),
        ])
    } else {
        let bindings: Vec<(&str, &str)> = match app.page {
            Page::Main => vec![
                ("←→↑↓", "Navigate"),
                ("t", "Toggle"),
                ("Enter", "Edit"),
                ("p", "Preview"),
                ("Space", "Play"),
                ("<>", "Length"),
                ("[]", "Speed"),
            ],
            Page::Patterns => vec![
                ("←→↑↓", "Navigate"),
                ("Enter", "Select"),
                ("Space", "Play"),
                ("Esc", "Back"),
                ("r", "Rename"),
                ("Del", "Reset"),
            ],
            Page::Engine => vec![
                ("Tab", "Section"),
                ("←→", "Switch/Adjust"),
                ("↑↓", "Navigate"),
                ("Enter", "Select"),
                ("A", "Add path"),
            ],
            Page::Options => vec![
                ("Tab", "Next"),
                ("←→", "Toggle"),
                ("Space", "Play"),
            ],
            Page::Help => vec![
                ("↑↓", "Scroll"),
                ("Tab", "Topic"),
                ("PgUp/Dn", "Page"),
            ],
            Page::Dict => vec![
                ("Tab", "Focus"),
                ("↑↓", "Navigate"),
                ("/", "Search"),
            ],
        };

        let page_width = page_indicator.chars().count();
        let bindings_content_width: usize = bindings
            .iter()
            .map(|(k, a)| k.chars().count() + 1 + a.chars().count())
            .sum();

        let n = bindings.len();
        let total_content = page_width + bindings_content_width;
        let total_gaps = available_width.saturating_sub(total_content);
        let gap_count = n + 1;
        let base_gap = total_gaps / gap_count;
        let extra = total_gaps % gap_count;

        let mut spans = vec![
            Span::styled(
                page_indicator.to_string(),
                Style::new().fg(Color::White).add_modifier(Modifier::DIM),
            ),
            Span::raw(" ".repeat(base_gap + if extra > 0 { 1 } else { 0 })),
        ];

        for (i, (key, action)) in bindings.into_iter().enumerate() {
            spans.push(Span::styled(
                key.to_string(),
                Style::new().fg(Color::Yellow),
            ));
            spans.push(Span::styled(
                format!(":{action}"),
                Style::new().fg(Color::Rgb(120, 125, 135)),
            ));

            if i < n - 1 {
                let gap = base_gap + if i + 1 < extra { 1 } else { 0 };
                spans.push(Span::raw(" ".repeat(gap)));
            }
        }

        Line::from(spans)
    };

    let footer = Paragraph::new(content).block(block);
    frame.render_widget(footer, area);
}

fn render_modal(frame: &mut Frame, app: &App, snapshot: &SequencerSnapshot, term: Rect) {
    match &app.ui.modal {
        Modal::None => {}
        Modal::ConfirmQuit { selected } => {
            ConfirmModal::new("Confirm", "Quit?", *selected).render_centered(frame, term);
        }
        Modal::ConfirmDeleteStep { step, selected, .. } => {
            ConfirmModal::new("Confirm", &format!("Delete step {}?", step + 1), *selected)
                .render_centered(frame, term);
        }
        Modal::ConfirmResetPattern {
            pattern, selected, ..
        } => {
            ConfirmModal::new(
                "Confirm",
                &format!("Reset pattern {}?", pattern + 1),
                *selected,
            )
            .render_centered(frame, term);
        }
        Modal::ConfirmResetBank { bank, selected } => {
            ConfirmModal::new("Confirm", &format!("Reset bank {}?", bank + 1), *selected)
                .render_centered(frame, term);
        }
        Modal::FileBrowser(state) => {
            use crate::state::file_browser::FileBrowserMode;
            use crate::widgets::FileBrowserModal;
            let (title, border_color) = match state.mode {
                FileBrowserMode::Save => ("Save As", Color::Green),
                FileBrowserMode::Load => ("Load From", Color::Blue),
            };
            let entries: Vec<(String, bool)> = state
                .entries
                .iter()
                .map(|e| (e.name.clone(), e.is_dir))
                .collect();
            FileBrowserModal::new(title, &state.input, &entries)
                .selected(state.selected)
                .scroll_offset(state.scroll_offset)
                .border_color(border_color)
                .width(60)
                .height(18)
                .render_centered(frame, term);
        }
        Modal::RenameBank { bank, name } => {
            TextInputModal::new(&format!("Rename Bank {:02}", bank + 1), name)
                .width(40)
                .border_color(Color::Magenta)
                .render_centered(frame, term);
        }
        Modal::RenamePattern {
            bank,
            pattern,
            name,
        } => {
            TextInputModal::new(
                &format!("Rename B{:02}:P{:02}", bank + 1, pattern + 1),
                name,
            )
            .width(40)
            .border_color(Color::Magenta)
            .render_centered(frame, term);
        }
        Modal::SetPattern { field, input } => {
            let (title, hint) = match field {
                PatternField::Length => ("Set Length (1-128)", "Enter number"),
                PatternField::Speed => ("Set Speed", "1/8x, 1/4x, 1/2x, 1x, 2x, 4x, 8x"),
            };
            TextInputModal::new(title, input)
                .hint(hint)
                .width(45)
                .border_color(Color::Yellow)
                .render_centered(frame, term);
        }
        Modal::SetTempo(input) => {
            TextInputModal::new("Set Tempo (20-300 BPM)", input)
                .hint("Enter BPM")
                .width(30)
                .border_color(Color::Magenta)
                .render_centered(frame, term);
        }
        Modal::AddSamplePath(state) => {
            use crate::widgets::FileBrowserModal;
            let entries: Vec<(String, bool)> = state
                .entries
                .iter()
                .map(|e| (e.name.clone(), e.is_dir))
                .collect();
            FileBrowserModal::new("Add Sample Path", &state.input, &entries)
                .selected(state.selected)
                .scroll_offset(state.scroll_offset)
                .border_color(Color::Magenta)
                .width(60)
                .height(18)
                .render_centered(frame, term);
        }
        Modal::Preview => {
            let width = (term.width * 80 / 100).max(40);
            let height = (term.height * 80 / 100).max(10);

            let pattern = app.current_edit_pattern();
            let step_idx = app.editor_ctx.step;
            let step = pattern.step(step_idx);
            let source_idx = step.and_then(|s| s.source);

            let title = if let Some(src) = source_idx {
                format!("Step {:02} → {:02}", step_idx + 1, src + 1)
            } else {
                format!("Step {:02}", step_idx + 1)
            };

            let inner = ModalFrame::new(&title)
                .width(width)
                .height(height)
                .border_color(Color::Rgb(120, 125, 135))
                .render_centered(frame, term);

            let script = pattern.resolve_script(step_idx).unwrap_or("");
            if script.is_empty() {
                let empty = Paragraph::new("(empty)")
                    .alignment(Alignment::Center)
                    .style(Style::new().fg(Color::Rgb(80, 85, 95)));
                let centered_area = Rect {
                    y: inner.y + inner.height / 2,
                    height: 1,
                    ..inner
                };
                frame.render_widget(empty, centered_area);
            } else {
                let trace = if app.ui.runtime_highlight && app.playback.playing {
                    let source = pattern.resolve_source(step_idx);
                    snapshot.get_trace(app.editor_ctx.bank, app.editor_ctx.pattern, source)
                } else {
                    None
                };

                let mut line_start = 0usize;
                let lines: Vec<Line> = script
                    .lines()
                    .map(|line_str| {
                        let tokens = if let Some(t) = trace {
                            let exec = adjust_spans_for_line(&t.executed_spans, line_start, line_str.len());
                            let sel = adjust_spans_for_line(&t.selected_spans, line_start, line_str.len());
                            highlight_line_with_runtime(line_str, &exec, &sel)
                        } else {
                            highlight_line(line_str)
                        };
                        line_start += line_str.len() + 1;
                        let spans: Vec<Span> = tokens
                            .into_iter()
                            .map(|(style, text)| Span::styled(text, style))
                            .collect();
                        Line::from(spans)
                    })
                    .collect();

                let paragraph = Paragraph::new(lines);
                frame.render_widget(paragraph, inner);
            }
        }
        Modal::Editor => {
            let width = (term.width * 80 / 100).max(40);
            let height = (term.height * 60 / 100).max(10);
            let step_num = app.editor_ctx.step + 1;

            let flash_kind = app.ui.flash_kind();
            let border_color = match flash_kind {
                Some(FlashKind::Error) => Color::Red,
                Some(FlashKind::Info) => Color::White,
                Some(FlashKind::Success) => Color::Green,
                None => Color::Rgb(100, 160, 180),
            };

            let inner = ModalFrame::new(&format!("Step {step_num:02} Script"))
                .width(width)
                .height(height)
                .border_color(border_color)
                .render_centered(frame, term);

            let trace = if app.ui.runtime_highlight && app.playback.playing {
                let source = app.current_edit_pattern().resolve_source(app.editor_ctx.step);
                snapshot.get_trace(app.editor_ctx.bank, app.editor_ctx.pattern, source)
            } else {
                None
            };

            let text_lines = app.editor_ctx.editor.lines();
            let mut line_offsets: Vec<usize> = Vec::with_capacity(text_lines.len());
            let mut offset = 0;
            for line in text_lines.iter() {
                line_offsets.push(offset);
                offset += line.len() + 1;
            }

            let highlighter = |row: usize, line: &str| -> Vec<(Style, String)> {
                let line_start = line_offsets[row];
                let (exec, sel) = match trace {
                    Some(t) => (
                        adjust_spans_for_line(&t.executed_spans, line_start, line.len()),
                        adjust_spans_for_line(&t.selected_spans, line_start, line.len()),
                    ),
                    None => (Vec::new(), Vec::new()),
                };
                highlight::highlight_line_with_runtime(line, &exec, &sel)
            };

            let show_search = app.editor_ctx.editor.search_active()
                || !app.editor_ctx.editor.search_query().is_empty();

            let (search_area, editor_area, hint_area) = if show_search {
                let search_area = Rect::new(inner.x, inner.y, inner.width, 1);
                let editor_area = Rect::new(inner.x, inner.y + 1, inner.width, inner.height.saturating_sub(2));
                let hint_area = Rect::new(inner.x, inner.y + 1 + editor_area.height, inner.width, 1);
                (Some(search_area), editor_area, hint_area)
            } else {
                let editor_area = Rect::new(inner.x, inner.y, inner.width, inner.height.saturating_sub(1));
                let hint_area = Rect::new(inner.x, inner.y + editor_area.height, inner.width, 1);
                (None, editor_area, hint_area)
            };

            if let Some(sa) = search_area {
                let style = if app.editor_ctx.editor.search_active() {
                    Style::default().fg(Color::Yellow)
                } else {
                    Style::default().fg(Color::DarkGray)
                };
                let cursor = if app.editor_ctx.editor.search_active() { "_" } else { "" };
                let text = format!("/{}{}", app.editor_ctx.editor.search_query(), cursor);
                frame.render_widget(Paragraph::new(Line::from(Span::styled(text, style))), sa);
            }

            if let Some(kind) = flash_kind {
                let bg = match kind {
                    FlashKind::Error => Color::Rgb(60, 10, 10),
                    FlashKind::Info => Color::Rgb(30, 30, 40),
                    FlashKind::Success => Color::Rgb(10, 30, 10),
                };
                let flash_block = Block::default().style(Style::default().bg(bg));
                frame.render_widget(flash_block, editor_area);
            }
            app.editor_ctx.editor.render(frame, editor_area, &highlighter);

            let dim = Style::default().fg(Color::DarkGray);
            let key = Style::default().fg(Color::Yellow);
            let hint = if app.editor_ctx.editor.search_active() {
                Line::from(vec![
                    Span::styled("Enter", key), Span::styled(" confirm  ", dim),
                    Span::styled("Esc", key), Span::styled(" cancel", dim),
                ])
            } else {
                Line::from(vec![
                    Span::styled("Esc", key), Span::styled(" save  ", dim),
                    Span::styled("C-e", key), Span::styled(" eval  ", dim),
                    Span::styled("C-f", key), Span::styled(" find  ", dim),
                    Span::styled("C-n", key), Span::styled("/", dim),
                    Span::styled("C-p", key), Span::styled(" next/prev  ", dim),
                    Span::styled("C-u", key), Span::styled("/", dim),
                    Span::styled("C-r", key), Span::styled(" undo/redo", dim),
                ])
            };
            frame.render_widget(Paragraph::new(hint).alignment(Alignment::Right), hint_area);
        }
    }
}