use eframe::egui;
use crate::book::Book;
use crate::style::{StyleProfile, TextAlignment};
use crate::theme::{self, BgType, Theme};

pub fn recalculate_pages(book: &mut Book, font_size: f32, line_height: f32, panel_width: f32, panel_height: f32, style: &StyleProfile) {
    let char_width = font_size * 1.0;
    let safety = 0.95;
    let chars_per_line = if char_width > 0.0 {
        ((panel_width / char_width) * safety).max(1.0) as usize
    } else {
        1
    };
    let lines_per_page = if line_height > 0.0 {
        ((panel_height / line_height) * safety).max(1.0) as usize
    } else {
        1
    };
    let chars_per_page = chars_per_line * lines_per_page;
    for section in &mut book.sections {
        let styled = style.apply_to_text(&section.content);
        section.pages = calculate_pages(&styled, chars_per_page);
    }
}

pub struct ReaderAction {
    pub go_back: bool,
    pub toggle_theme: bool,
    pub toggle_bookmark: bool,
    pub switch_bg: Option<BgType>,
    pub switch_to_profile: Option<String>,
    pub page_next: bool,
    pub page_prev: bool,
}

pub fn reading_view(
    ui: &mut egui::Ui,
    book: &mut Book,
    current_section: &mut usize,
    current_page: &mut usize,
    sidebar_open: &mut bool,
    style: &mut StyleProfile,
    theme: &Theme,
    bg_type: BgType,
    _file_path: &str,
    profile_names: &[String],
    bookmarks: &[crate::theme::Bookmark],
) -> (ReaderAction, Option<usize>) {
    let mut action = ReaderAction {
        go_back: false,
        toggle_theme: false,
        toggle_bookmark: false,
        switch_bg: None,
        switch_to_profile: None,
        page_next: false,
        page_prev: false,
    };
    let mut jump_to_bookmark: Option<usize> = None;

      let colors = theme::reader_colors(theme);

     let has_bookmark = bookmarks.iter().any(|b| b.section == *current_section && b.page == *current_page);

    // --- Sidebar (TOC + Bookmarks) ---
    let sidebar_tab_id = ui.make_persistent_id("sidebar_tab");
    let mut sidebar_tab: usize = ui.data_mut(|d| *d.get_temp_mut_or_default::<usize>(sidebar_tab_id));

    if *sidebar_open {
        egui::SidePanel::left("toc_sidebar")
            .resizable(true)
            .default_width(240.0)
            .show_inside(ui, |ui| {
                ui.horizontal(|ui| {
                    let toc_response = ui.selectable_label(sidebar_tab == 0, "📋 目录");
                    let bm_response = ui.selectable_label(sidebar_tab == 1,
                        format!("🔖 书签 ({})", bookmarks.len())
                    );
                    if toc_response.clicked() {
                        sidebar_tab = 0;
                        ui.data_mut(|d| *d.get_temp_mut_or_default::<usize>(sidebar_tab_id) = 0);
                    }
                    if bm_response.clicked() {
                        sidebar_tab = 1;
                        ui.data_mut(|d| *d.get_temp_mut_or_default::<usize>(sidebar_tab_id) = 1);
                    }
                });
                ui.separator();
                if sidebar_tab == 0 {
                    render_toc(ui, &book.toc, current_section, current_page);
                } else {
                    render_bookmarks(ui, bookmarks, &mut jump_to_bookmark);
                }
            });
    }

    // --- Top toolbar ---
    egui::TopBottomPanel::top("reader_toolbar")
        .show_inside(ui, |ui| {
            ui.horizontal(|ui| {
                if ui.button("← 返回").on_hover_text("返回书架").clicked() {
                    action.go_back = true;
                }
                ui.separator();
                ui.label(&book.title);
                ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
                    let (theme_icon, theme_hint) = match theme {
                        Theme::Dark => ("🌞", "切换到浅色主题"),
                        Theme::Light => ("🌙", "切换到夜间主题"),
                        Theme::Sepia => ("📜", "切换到棕褐色主题"),
                    };
                    if ui.button(theme_icon).on_hover_text(theme_hint).clicked() {
                        action.toggle_theme = true;
                    }
                    let bookmark_icon = if has_bookmark { "🔴" } else { "🔖" };
                    let bookmark_hint = if has_bookmark { "移除书签" } else { "添加书签" };
                    if ui.button(bookmark_icon).on_hover_text(bookmark_hint).clicked() {
                        action.toggle_bookmark = true;
                    }
                    if ui.button("A⁻").on_hover_text("缩小字体").clicked() {
                        style.font_size = (style.font_size - 2.0).max(10.0);
                    }
                    if ui.button("A⁺").on_hover_text("放大字体").clicked() {
                        style.font_size = (style.font_size + 2.0).min(48.0);
                    }
                    egui::ComboBox::from_id_salt("profile_selector")
                        .width(110.0)
                        .selected_text(&style.name)
                        .show_ui(ui, |ui| {
                            for name in profile_names {
                                let selected = *name == style.name;
                                if ui.selectable_label(selected, name).clicked() {
                                    action.switch_to_profile = Some(name.clone());
                                }
                            }
                        });
egui::ComboBox::from_id_salt("bg_type_selector")
                         .width(100.0)
                         .selected_text(bg_type.label())
                         .show_ui(ui, |ui| {
                             for &label in BgType::ALL.iter() {
                                 let selected = bg_type.label() == label;
                                 if ui.selectable_label(selected, label).clicked() {
                                     action.switch_bg = Some(theme::BgType::from_label(label));
                                 }
                             }
                         });
                    if ui.button("☰").on_hover_text("打开/关闭目录").clicked() {
                        *sidebar_open = !*sidebar_open;
                    }
                });
            });
        });

    // 在工具条之后、进度条之前用当前可用高度重新分页
    let panel_size = ui.available_size();
    let recalc_width = (panel_size.x - 48.0).max(100.0);
    let recalc_height = (panel_size.y - 60.0).max(200.0);
    recalculate_pages(book, style.font_size, style.line_height(), recalc_width, recalc_height, style);

    // --- Bottom progress bar ---
    let total_pages = if *current_section < book.sections.len() {
        let p = &book.sections[*current_section].pages;
        if p.len() > 1 { p.len() - 1 } else { 0 }
    } else { 0 };

    egui::TopBottomPanel::bottom("reader_progress")
        .show_inside(ui, |ui| {
            ui.horizontal(|ui| {
                let section_title = book.sections.get(*current_section)
                    .map(|s| s.title.as_str())
                    .unwrap_or("");
                ui.label(section_title);
                ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
                    // Page turn buttons (right side of bottom bar)
                    let prev_enabled = *current_page > 0 || *current_section > 0;
                    let next_enabled = (*current_page + 1 < book.sections[*current_section]
                        .pages.len().saturating_sub(1))
                        || (*current_section + 1 < book.sections.len());

                    let next_btn = egui::Button::new(
                        egui::RichText::new("下一页 ▶").size(13.0)
                    ).min_size(egui::vec2(100.0, 28.0));

                    let prev_btn = egui::Button::new(
                        egui::RichText::new("◀ 上一页").size(13.0)
                    ).min_size(egui::vec2(100.0, 28.0));

                    if !next_enabled {
                        ui.add_enabled(false, next_btn);
                    } else if ui.add(next_btn).on_hover_text("下一页 (→键)").clicked() {
                        action.page_next = true;
                    }

                    ui.add_space(8.0);

                    if !prev_enabled {
                        ui.add_enabled(false, prev_btn);
                    } else if ui.add(prev_btn).on_hover_text("上一页 (←键)").clicked() {
                        action.page_prev = true;
                    }

                    ui.separator();

                    let label = if total_pages > 0 {
                        format!("{}/{}", *current_page + 1, total_pages)
                    } else {
                        "1/1".to_string()
                    };
                    ui.label(label);
                    let mut progress = if total_pages > 0 {
                        *current_page as f32 / total_pages as f32
                    } else { 0.0 };
                    if ui.add(egui::Slider::new(&mut progress, 0.0..=1.0).text("")).changed() && total_pages > 0 {
                        *current_page = (progress * total_pages as f32).round() as usize;
                    }
                });
            });
        });

// --- Center text area ---
     egui::CentralPanel::default().show_inside(ui, |ui| {
         let available = ui.available_size();
         let (rect, response) = ui.allocate_at_least(available, egui::Sense::click());

         // Add reading margins (inset)
          let inset = 24.0;
          let text_rect = egui::Rect::from_min_size(
              egui::pos2(rect.min.x + inset, rect.min.y),
              egui::vec2((rect.width() - inset * 2.0).max(100.0), rect.height()),
          );

// 分页已在工具条之后统一计算（使用当前可用高度），此处不再重复
          if let Some(section) = book.sections.get(*current_section) {
              let max_page = section.pages.len().saturating_sub(2);
              if *current_page > max_page {
                  *current_page = max_page;
              }
          }

         if let Some(section) = book.sections.get(*current_section) {
            if *current_page < section.pages.len().saturating_sub(1) {
                let start = section.pages[*current_page];
                let end = section.pages[*current_page + 1];
                let styled_full = style.apply_to_text(&section.content);
                let page_text: String = styled_full.chars().skip(start).take(end - start).collect();

                let align = match style.alignment {
                    TextAlignment::Left => egui::Align::LEFT,
                    TextAlignment::Center => egui::Align::Center,
                    TextAlignment::Right => egui::Align::RIGHT,
                };
                ui.allocate_new_ui(egui::UiBuilder::new().max_rect(text_rect), |ui| {
                    ui.with_layout(
                        egui::Layout::top_down(align).with_main_justify(false),
                        |ui| {
                            let mut is_heading = false;
                            let mut text_start = 0usize;
                            let char_indices: Vec<_> = page_text.char_indices().collect();
                            let mut idx = 0;
                            while idx < char_indices.len() {
                                let (byte_pos, ch) = char_indices[idx];
                                if ch == '\x01' || ch == '\x02' {
                                    if byte_pos > text_start {
                                        let text = &page_text[text_start..byte_pos];
                                        let mut rt = egui::RichText::new(text)
                                            .size(style.font_size)
                                            .color(colors.text);
                                        if is_heading {
                                            rt = rt.strong();
                                        }
                                        ui.add(egui::Label::new(rt).wrap());
                                    }
                                    is_heading = ch == '\x01';
                                    idx += 1;
                                    if idx < char_indices.len() {
                                        text_start = char_indices[idx].0;
                                    } else {
                                        text_start = page_text.len();
                                    }
                                } else {
                                    idx += 1;
                                }
                            }
                            if text_start < page_text.len() {
                                let text = &page_text[text_start..];
                                let mut rt = egui::RichText::new(text)
                                    .size(style.font_size)
                                    .color(colors.text);
                                if is_heading {
                                    rt = rt.strong();
                                }
                                ui.add(egui::Label::new(rt).wrap());
                            }
                        },
                    );
                });

                if has_bookmark {
                    let painter = ui.painter();
                    let bookmark_pos = egui::pos2(rect.max.x - 30.0, rect.min.y + 10.0);
                    painter.text(
                        bookmark_pos,
                        egui::Align2::RIGHT_TOP,
                        "🔴",
                        egui::FontId::proportional(18.0),
                        egui::Color32::RED,
                    );
                }
            }
        }

        // Click navigation
        if response.clicked() {
            if let Some(click_pos) = response.interact_pointer_pos() {
                let x_ratio = (click_pos.x - rect.min.x) / rect.width();
                if x_ratio < 0.3 {
                    action.page_prev = true;
                } else if x_ratio > 0.7 {
                    action.page_next = true;
                }
            }
        }

        // Keyboard navigation
        if ui.input(|i| i.key_pressed(egui::Key::ArrowRight)) {
            action.page_next = true;
        }
        if ui.input(|i| i.key_pressed(egui::Key::ArrowLeft)) {
            action.page_prev = true;
        }
    });

    (action, jump_to_bookmark)
}

fn render_toc(
    ui: &mut egui::Ui,
    entries: &[crate::book::TocEntry],
    current_section: &mut usize,
    current_page: &mut usize,
) {
    for entry in entries {
        let is_current = entry.section == *current_section;
        let label_text = if is_current {
            egui::RichText::new(&entry.label).color(egui::Color32::YELLOW).strong()
        } else {
            egui::RichText::new(&entry.label)
        };
        let response = ui.add(
            egui::Button::new(label_text)
                .frame(false)
                .wrap()
        );
        if response.clicked() {
            *current_section = entry.section;
            *current_page = 0;
        }
        response.on_hover_text(format!("跳转到: {}", entry.label));
        if !entry.children.is_empty() {
            ui.indent(&entry.label, |ui| {
                render_toc(ui, &entry.children, current_section, current_page);
            });
        }
    }
}

fn render_bookmarks(
    ui: &mut egui::Ui,
    bookmarks: &[crate::theme::Bookmark],
    jump_to_bookmark: &mut Option<usize>,
) {
    if bookmarks.is_empty() {
        ui.horizontal(|ui| {
            ui.label("暂无书签");
        });
        ui.label("点击工具栏 🔖 按钮添加书签");
        return;
    }

    for (idx, bm) in bookmarks.iter().enumerate() {
        let label_text = egui::RichText::new(&bm.label).size(13.0);
        if ui.add(
            egui::Button::new(label_text)
                .frame(false)
                .wrap()
        ).on_hover_text("点击跳转到该书签").clicked() {
            *jump_to_bookmark = Some(idx);
        }
    }
}

pub fn calculate_pages(text: &str, chars_per_page: usize) -> Vec<usize> {
    let mut pages = Vec::new();
    pages.push(0);

    if text.is_empty() || chars_per_page == 0 {
        return pages;
    }

    let chars: Vec<char> = text.chars().collect();
    let total_chars = chars.len();
    if total_chars <= chars_per_page {
        pages.push(total_chars);
        return pages;
    }

    let mut pos: usize = 0;
    while pos < total_chars {
        let next = pos + chars_per_page;
        if next >= total_chars {
            pages.push(total_chars);
            break;
        }

        // Search backward from next for paragraph (\n\n) or line (\n) breaks
        let search_start = pos + chars_per_page / 2;
        let search_end = (next + chars_per_page / 2).min(total_chars);
        let mut split = next;

        // Prefer double newline (paragraph), then single newline
        let mut found = false;
        for i in (search_start..search_end).rev() {
            if chars[i] == '\n' && i > 0 && chars[i - 1] == '\n' {
                split = i - 1;
                found = true;
                break;
            }
        }
        if !found {
            for i in (search_start..search_end).rev() {
                if chars[i] == '\n' {
                    split = i + 1;
                    break;
                }
            }
        }

        if split <= pos {
            split = next;
        }

        pos = split.min(total_chars);
        pages.push(pos);
    }

    pages
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_pagination_empty() {
        let pages = calculate_pages("", 100);
        assert_eq!(pages, vec![0]);
    }

    #[test]
    fn test_pagination_shorter_than_page() {
        let pages = calculate_pages("Hello World", 100);
        assert_eq!(pages, vec![0, 11]);
    }

    #[test]
    fn test_pagination_exact_fit() {
        let pages = calculate_pages("ABCD", 4);
        assert_eq!(pages, vec![0, 4]);
    }

    #[test]
    fn test_pagination_multiple_pages() {
        let text = "A".repeat(100);
        let pages = calculate_pages(&text, 30);
        assert_eq!(pages, vec![0, 30, 60, 90, 100]);
    }

    #[test]
    fn test_pagination_single_char() {
        let pages = calculate_pages("A", 1);
        assert_eq!(pages, vec![0, 1]);
    }

    #[test]
    fn test_pagination_zero_chars_per_page() {
        let pages = calculate_pages("test", 0);
        assert_eq!(pages, vec![0]);
    }
}