//! TUI rendering: frame layout, conversation display, and scroll management.

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

use super::{AppState, Mode};
use crate::core::types::Role;

/// Estimate the total rendered line count for all messages and update `state.scroll`
/// so the bottom of the content is visible.
///
/// When content fits within the viewport, `state.scroll` is set to 0.
///
/// Line estimation per message:
/// - 1 line for the role header
/// - `ceil(chars / width).max(1)` lines per newline-separated content line
/// - 1 blank separator line
pub(super) fn update_scroll(state: &mut AppState, area: Rect) {
    // 4 = input pane (3: border top + content + border bottom) + status bar (1)
    let viewport_height = area.height.saturating_sub(4);
    state.viewport_height = viewport_height;
    let width = area.width.max(1) as usize;

    let mut total_lines: u16 = 0;
    for (_, content) in &state.messages {
        total_lines = total_lines.saturating_add(1); // role header
        for line in content.lines() {
            let chars = line.chars().count();
            let wrapped = chars.div_ceil(width).max(1) as u16;
            total_lines = total_lines.saturating_add(wrapped);
        }
        total_lines = total_lines.saturating_add(1); // blank separator
    }

    let max_scroll = total_lines.saturating_sub(viewport_height);

    match state.mode {
        // In Insert mode, auto-follow the bottom of the conversation.
        Mode::Insert => {
            state.scroll = max_scroll;
        }
        // In Normal/Command mode, the user controls scroll -- just clamp to bounds.
        _ => {
            state.scroll = state.scroll.min(max_scroll);
        }
    }
}

/// Compute the overlay rectangle for the command palette, centered on `output_area`.
fn command_overlay_rect(output_area: Rect) -> Rect {
    let overlay_w = (output_area.width / 2).max(80).min(output_area.width);
    let overlay_h: u16 = 3; // border + content + border
    let overlay_x = output_area.x + (output_area.width.saturating_sub(overlay_w)) / 2;
    let overlay_y = output_area.y + 2;
    Rect {
        x: overlay_x,
        y: overlay_y,
        width: overlay_w,
        height: overlay_h.min(output_area.height),
    }
}

/// Render the full TUI into `frame`.
///
/// Layout (top to bottom):
/// ```text
/// +--------------------------------+
/// |  conversation history          |  Fill(1)
/// |                                |
/// +--------------------------------+
/// |  Input                         |  Length(3)
/// |  > _                           |
/// +--------------------------------+
/// | NORMAL          tokens: --     |  Length(1)
/// +--------------------------------+
/// ```
///
/// Role headers are coloured: `"You:"` in cyan, `"Assistant:"` in green.
/// In Command mode, a one-line overlay appears at row 1 of the output pane.
pub(super) fn render(frame: &mut Frame, state: &AppState) {
    let chunks = Layout::vertical([
        Constraint::Fill(1),
        Constraint::Length(3),
        Constraint::Length(1),
    ])
    .split(frame.area());

    // --- Output pane ---
    let mut lines: Vec<Line> = Vec::new();
    for (role, content) in &state.messages {
        let (label, color) = match role {
            Role::User => ("You:", Color::Cyan),
            Role::Assistant => ("Assistant:", Color::Green),
        };
        lines.push(Line::from(Span::styled(label, Style::default().fg(color))));
        for body_line in content.lines() {
            lines.push(Line::from(body_line.to_string()));
        }
        lines.push(Line::from("")); // blank separator
    }

    let output = Paragraph::new(lines)
        .wrap(Wrap { trim: false })
        .scroll((state.scroll, 0));
    let output_area = chunks[0];
    frame.render_widget(output, output_area);

    // --- Tool approval overlay ---
    if let Some(ref approval) = state.pending_approval {
        let overlay_w = (output_area.width / 2).max(60).min(output_area.width);
        let overlay_h: u16 = 5;
        let overlay_x = output_area.x + (output_area.width.saturating_sub(overlay_w)) / 2;
        let overlay_y = output_area.y + output_area.height.saturating_sub(overlay_h) / 2;
        let overlay_area = Rect {
            x: overlay_x,
            y: overlay_y,
            width: overlay_w,
            height: overlay_h.min(output_area.height),
        };
        frame.render_widget(Clear, overlay_area);
        let text = format!(
            "{}: {}\n\ny = approve, n = deny",
            approval.tool_name, approval.input_summary
        );
        let overlay = Paragraph::new(text).block(
            Block::bordered()
                .border_style(Style::default().fg(Color::Yellow))
                .title("Tool Approval"),
        );
        frame.render_widget(overlay, overlay_area);
    }

    // --- Command overlay (floating box centered on output pane) ---
    if state.mode == Mode::Command {
        let overlay_area = command_overlay_rect(output_area);
        // Clear the area behind the overlay so it appears floating.
        frame.render_widget(Clear, overlay_area);
        let overlay = Paragraph::new(format!(":{}", state.command_buffer)).block(
            Block::bordered()
                .border_style(Style::default().fg(Color::Yellow))
                .title("Command"),
        );
        frame.render_widget(overlay, overlay_area);
    }

    // --- Input pane ---
    let (input_title, input_style) = match state.mode {
        Mode::Normal | Mode::Command => (
            "Input (normal)",
            Style::default()
                .fg(Color::DarkGray)
                .add_modifier(Modifier::ITALIC),
        ),
        Mode::Insert => ("Input", Style::default()),
    };
    let input_text = format!("> {}", state.input);
    let input_widget = Paragraph::new(input_text)
        .style(input_style)
        .block(Block::bordered().title(input_title));
    frame.render_widget(input_widget, chunks[1]);

    // --- Cursor positioning ---
    match state.mode {
        Mode::Insert => {
            // Cursor at end of input text: border(1) + "> " (2) + input len
            let cursor_x = chunks[1].x + 1 + 2 + state.input.len() as u16;
            let cursor_y = chunks[1].y + 1; // inside the border
            frame.set_cursor_position((cursor_x, cursor_y));
        }
        Mode::Command => {
            // Cursor in the floating overlay
            let overlay = command_overlay_rect(output_area);
            // border(1) + ":" (1) + buf len
            let cursor_x = overlay.x + 1 + 1 + state.command_buffer.len() as u16;
            let cursor_y = overlay.y + 1; // inside the border
            frame.set_cursor_position((cursor_x, cursor_y));
        }
        Mode::Normal => {} // no cursor
    }

    // --- Status bar ---
    let (mode_label, mode_style) = match state.mode {
        Mode::Normal => (
            " NORMAL ",
            Style::default().bg(Color::Blue).fg(Color::White),
        ),
        Mode::Insert => (
            " INSERT ",
            Style::default().bg(Color::Green).fg(Color::White),
        ),
        Mode::Command => (
            " COMMAND ",
            Style::default().bg(Color::Yellow).fg(Color::Black),
        ),
    };

    let right_text = if let Some(ref err) = state.status_error {
        err.clone()
    } else {
        "tokens: --".to_string()
    };

    let right_style = if state.status_error.is_some() {
        Style::default().fg(Color::Red)
    } else {
        Style::default()
    };

    let bar_width = chunks[2].width as usize;
    let left_len = mode_label.len();
    let right_len = right_text.len();
    let pad = bar_width.saturating_sub(left_len + right_len);

    let status_line = Line::from(vec![
        Span::styled(mode_label, mode_style),
        Span::raw(" ".repeat(pad)),
        Span::styled(right_text, right_style),
    ]);
    let status_widget = Paragraph::new(status_line);
    frame.render_widget(status_widget, chunks[2]);
}

#[cfg(test)]
mod tests {
    use super::*;
    use ratatui::Terminal;
    use ratatui::backend::TestBackend;

    #[test]
    fn render_smoke_test() {
        let backend = TestBackend::new(80, 24);
        let mut terminal = Terminal::new(backend).unwrap();
        let state = AppState::new();
        terminal.draw(|frame| render(frame, &state)).unwrap();
        // no panic is the assertion
    }

    #[test]
    fn render_shows_role_prefixes() {
        let backend = TestBackend::new(80, 24);
        let mut terminal = Terminal::new(backend).unwrap();
        let mut state = AppState::new();
        state.messages.push((Role::User, "hi".to_string()));
        state.messages.push((Role::Assistant, "hello".to_string()));
        terminal.draw(|frame| render(frame, &state)).unwrap();
        let buf = terminal.backend().buffer().clone();
        let all_text: String = buf
            .content()
            .iter()
            .map(|c| c.symbol().to_string())
            .collect();
        assert!(
            all_text.contains("You:"),
            "expected 'You:' in buffer: {all_text:.100}"
        );
        assert!(
            all_text.contains("Assistant:"),
            "expected 'Assistant:' in buffer"
        );
    }

    // --- update_scroll tests ---

    #[test]
    fn update_scroll_zero_when_fits() {
        let mut state = AppState::new();
        state.messages.push((Role::User, "hello".to_string()));
        let area = Rect::new(0, 0, 80, 24);
        update_scroll(&mut state, area);
        assert_eq!(state.scroll, 0);
    }

    #[test]
    fn update_scroll_positive_when_overflow() {
        let mut state = AppState::new();
        for i in 0..50 {
            state.messages.push((Role::User, format!("message {i}")));
        }
        let area = Rect::new(0, 0, 80, 24);
        update_scroll(&mut state, area);
        assert!(state.scroll > 0, "expected scroll > 0 with 50 messages");
    }

    // --- render snapshot tests ---

    #[test]
    fn render_status_bar_normal_mode() {
        let backend = TestBackend::new(80, 24);
        let mut terminal = Terminal::new(backend).unwrap();
        let mut state = AppState::new();
        state.mode = Mode::Normal;
        terminal.draw(|frame| render(frame, &state)).unwrap();
        let buf = terminal.backend().buffer().clone();
        let all_text: String = buf
            .content()
            .iter()
            .map(|c| c.symbol().to_string())
            .collect();
        assert!(all_text.contains("NORMAL"), "expected 'NORMAL' in buffer");
        assert!(
            all_text.contains("tokens: --"),
            "expected 'tokens: --' in buffer"
        );
    }

    #[test]
    fn render_status_bar_insert_mode() {
        let backend = TestBackend::new(80, 24);
        let mut terminal = Terminal::new(backend).unwrap();
        let state = AppState::new(); // starts in Insert
        terminal.draw(|frame| render(frame, &state)).unwrap();
        let buf = terminal.backend().buffer().clone();
        let all_text: String = buf
            .content()
            .iter()
            .map(|c| c.symbol().to_string())
            .collect();
        assert!(all_text.contains("INSERT"), "expected 'INSERT' in buffer");
    }

    #[test]
    fn render_status_bar_command_mode() {
        let backend = TestBackend::new(80, 24);
        let mut terminal = Terminal::new(backend).unwrap();
        let mut state = AppState::new();
        state.mode = Mode::Command;
        terminal.draw(|frame| render(frame, &state)).unwrap();
        let buf = terminal.backend().buffer().clone();
        let all_text: String = buf
            .content()
            .iter()
            .map(|c| c.symbol().to_string())
            .collect();
        assert!(all_text.contains("COMMAND"), "expected 'COMMAND' in buffer");
    }

    #[test]
    fn render_command_overlay_visible_in_command_mode() {
        let backend = TestBackend::new(80, 24);
        let mut terminal = Terminal::new(backend).unwrap();
        let mut state = AppState::new();
        state.mode = Mode::Command;
        state.command_buffer = "quit".to_string();
        terminal.draw(|frame| render(frame, &state)).unwrap();
        let buf = terminal.backend().buffer().clone();
        let all_text: String = buf
            .content()
            .iter()
            .map(|c| c.symbol().to_string())
            .collect();
        assert!(
            all_text.contains(":quit"),
            "expected ':quit' overlay in buffer"
        );
    }

    #[test]
    fn render_no_overlay_in_normal_mode() {
        let backend = TestBackend::new(80, 24);
        let mut terminal = Terminal::new(backend).unwrap();
        let mut state = AppState::new();
        state.mode = Mode::Normal;
        terminal.draw(|frame| render(frame, &state)).unwrap();
        let buf = terminal.backend().buffer().clone();
        // Row 1 should not have a ":" prefix from the overlay
        let row1: String = (0..80)
            .map(|x| buf.cell((x, 1)).unwrap().symbol().to_string())
            .collect();
        assert!(
            !row1.starts_with(':'),
            "overlay should not appear in Normal mode"
        );
    }

    #[test]
    fn render_input_pane_dimmed_in_normal() {
        let backend = TestBackend::new(80, 24);
        let mut terminal = Terminal::new(backend).unwrap();
        let mut state = AppState::new();
        state.mode = Mode::Normal;
        terminal.draw(|frame| render(frame, &state)).unwrap();
        let buf = terminal.backend().buffer().clone();
        let all_text: String = buf
            .content()
            .iter()
            .map(|c| c.symbol().to_string())
            .collect();
        assert!(
            all_text.contains("Input (normal)"),
            "expected 'Input (normal)' title in Normal mode"
        );
    }

    #[test]
    fn render_status_bar_shows_error() {
        let backend = TestBackend::new(80, 24);
        let mut terminal = Terminal::new(backend).unwrap();
        let mut state = AppState::new();
        state.status_error = Some("Unknown command: foo".to_string());
        terminal.draw(|frame| render(frame, &state)).unwrap();
        let buf = terminal.backend().buffer().clone();
        let all_text: String = buf
            .content()
            .iter()
            .map(|c| c.symbol().to_string())
            .collect();
        assert!(
            all_text.contains("Unknown command: foo"),
            "expected error in status bar"
        );
    }

    #[test]
    fn render_approval_overlay_visible() {
        let backend = TestBackend::new(80, 24);
        let mut terminal = Terminal::new(backend).unwrap();
        let mut state = AppState::new();
        state.pending_approval = Some(super::super::events::PendingApproval {
            tool_use_id: "t1".to_string(),
            tool_name: "write_file".to_string(),
            input_summary: "path: foo.txt".to_string(),
        });
        terminal.draw(|frame| render(frame, &state)).unwrap();
        let buf = terminal.backend().buffer().clone();
        let all_text: String = buf
            .content()
            .iter()
            .map(|c| c.symbol().to_string())
            .collect();
        assert!(
            all_text.contains("Tool Approval"),
            "expected 'Tool Approval' overlay"
        );
        assert!(
            all_text.contains("write_file"),
            "expected tool name in overlay"
        );
    }
}