pdfboss-write 0.25.0

//! Document assembly: pages of canvas content, document metadata, and the
//! save path. `Pdf` is a plain struct — the fields are the composition,
//! and `Default` fills everything optional.

use std::path::Path;

use pdfboss_core::{Dict, Name, ObjRef, Object};

use crate::canvas::{Canvas, CanvasParts};
use crate::content::serialize_ops;
use crate::element::{self, Content};
use crate::error::{Error, Result};
use crate::font::Standard14;
use crate::sink::AsyncByteSink;
use crate::writer::{WriteOptions, Writer};

/// A page size, in default user-space units (1/72 inch), portrait.
#[derive(Debug, Clone, Copy, PartialEq, Default)]
pub enum PageSize {
    /// 297 × 420 mm.
    A3,
    /// 210 × 297 mm.
    #[default]
    A4,
    /// 148 × 210 mm.
    A5,
    /// 8.5 × 11 in.
    Letter,
    /// 8.5 × 14 in.
    Legal,
    /// Explicit dimensions in user-space units.
    Custom {
        /// Width in units.
        width: f32,
        /// Height in units.
        height: f32,
    },
}

impl PageSize {
    /// Width and height in user-space units.
    pub fn dimensions(self) -> (f32, f32) {
        match self {
            PageSize::A3 => (841.89, 1190.55),
            PageSize::A4 => (595.28, 841.89),
            PageSize::A5 => (419.53, 595.28),
            PageSize::Letter => (612.0, 792.0),
            PageSize::Legal => (612.0, 1008.0),
            PageSize::Custom { width, height } => (width, height),
        }
    }

    /// The same size with width and height swapped.
    pub fn landscape(self) -> PageSize {
        let (width, height) = self.dimensions();
        PageSize::Custom {
            width: height,
            height: width,
        }
    }

    /// Parses one of the five named sizes case-insensitively: `a3`, `a4`,
    /// `a5`, `letter`, `legal`. `None` for anything else — a custom size
    /// has no name to parse.
    pub fn by_name(name: &str) -> Option<PageSize> {
        match name.to_ascii_lowercase().as_str() {
            "a3" => Some(PageSize::A3),
            "a4" => Some(PageSize::A4),
            "a5" => Some(PageSize::A5),
            "letter" => Some(PageSize::Letter),
            "legal" => Some(PageSize::Legal),
            _ => None,
        }
    }
}

/// A calendar date and time with a UTC offset, for `/CreationDate` and
/// `/ModDate`. The writer never reads a clock — dates appear in output
/// only when a caller provides them, keeping builds reproducible.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Date {
    /// Four-digit year.
    pub year: u16,
    /// Month, 1–12.
    pub month: u8,
    /// Day of month, 1–31.
    pub day: u8,
    /// Hour, 0–23.
    pub hour: u8,
    /// Minute, 0–59.
    pub minute: u8,
    /// Second, 0–59.
    pub second: u8,
    /// Offset from UTC in minutes (positive east).
    pub utc_offset_minutes: i16,
}

impl Date {
    /// Formats as a PDF date string, `D:YYYYMMDDHHmmSSOHH'mm` — with a
    /// literal `Z` in place of the offset when the date is exactly UTC.
    pub fn to_pdf_string(self) -> String {
        let Date {
            year,
            month,
            day,
            hour,
            minute,
            second,
            utc_offset_minutes,
        } = self;
        let mut out = format!("D:{year:04}{month:02}{day:02}{hour:02}{minute:02}{second:02}");
        if utc_offset_minutes == 0 {
            out.push('Z');
            return out;
        }
        let sign = if utc_offset_minutes < 0 { '-' } else { '+' };
        let magnitude = utc_offset_minutes.unsigned_abs();
        out.push_str(&format!(
            "{sign}{:02}'{:02}",
            magnitude / 60,
            magnitude % 60
        ));
        out
    }

    /// Formats as an ISO-8601 date-time, `YYYY-MM-DDTHH:mm:SS±HH:MM` — with
    /// a literal `Z` in place of the offset when the date is exactly UTC.
    /// Used for the XMP `xmp:CreateDate`/`xmp:ModifyDate` elements.
    pub(crate) fn to_iso8601(self) -> String {
        let Date {
            year,
            month,
            day,
            hour,
            minute,
            second,
            utc_offset_minutes,
        } = self;
        let mut out = format!("{year:04}-{month:02}-{day:02}T{hour:02}:{minute:02}:{second:02}");
        if utc_offset_minutes == 0 {
            out.push('Z');
            return out;
        }
        let sign = if utc_offset_minutes < 0 { '-' } else { '+' };
        let magnitude = utc_offset_minutes.unsigned_abs();
        out.push_str(&format!(
            "{sign}{:02}:{:02}",
            magnitude / 60,
            magnitude % 60
        ));
        out
    }
}

/// Document information written to the `/Info` dictionary. Every field is
/// optional; an all-`None` value writes no dictionary at all.
#[derive(Debug, Clone, Default, PartialEq)]
pub struct Metadata {
    /// `/Title`.
    pub title: Option<String>,
    /// `/Author`.
    pub author: Option<String>,
    /// `/Subject`.
    pub subject: Option<String>,
    /// `/Keywords`.
    pub keywords: Option<String>,
    /// `/Creator` (the producing application's name).
    pub creator: Option<String>,
    /// `/Producer`.
    pub producer: Option<String>,
    /// `/CreationDate`.
    pub creation_date: Option<Date>,
    /// `/ModDate`.
    pub modification_date: Option<Date>,
}

/// One page: its size, rotation, painted content and link annotations.
#[derive(Debug, Default)]
pub struct Page {
    /// Page size (the `/MediaBox`).
    pub size: PageSize,
    /// Clockwise view rotation in degrees; must be a multiple of 90.
    pub rotation: i32,
    /// The page's painted content.
    pub canvas: Canvas,
    /// Composed elements, painted onto `canvas` at assemble time, after
    /// any content already painted there directly.
    pub content: Vec<Content>,
    /// Clickable link areas, emitted as `/Annots`.
    pub links: Vec<LinkAnnotation>,
}

/// A clickable rectangle on a page that opens a URI or jumps to a page in
/// the same document (a `/Link` annotation with a `/URI` or `/GoTo`
/// action; ISO 32000 §12.5.6.5, §12.6.4.7, §12.3.2).
#[derive(Debug, Clone, PartialEq)]
pub struct LinkAnnotation {
    /// The clickable area, `[x0, y0, x1, y1]` in the page's user space.
    pub rect: [f32; 4],
    /// Where the link goes.
    pub target: LinkTarget,
}

/// Where a [`LinkAnnotation`] leads.
#[derive(Debug, Clone, PartialEq)]
pub enum LinkTarget {
    /// An external URI, opened with a `/URI` action.
    Uri(String),
    /// A page within the same document, by index, opened with a `/GoTo`
    /// action that keeps the viewer's current position and zoom.
    Page(usize),
}

impl Page {
    /// An empty page of the given size.
    pub fn new(size: PageSize) -> Page {
        Page {
            size,
            ..Page::default()
        }
    }
}

/// A document's bookmark panel: an ordered forest of [`Bookmark`] nodes,
/// each linking to a page via an explicit `/XYZ` destination.
#[derive(Debug, Clone, Default, PartialEq)]
pub struct Outline {
    /// Top-level bookmarks, in reading order.
    pub bookmarks: Vec<Bookmark>,
}

/// One outline entry: a title, the page it jumps to, and nested children.
#[derive(Debug, Clone, Default, PartialEq)]
pub struct Bookmark {
    /// Text shown in the outline panel.
    pub title: String,
    /// Target page index, opened keeping the viewer's current position
    /// and zoom.
    pub page: usize,
    /// Nested bookmarks, in reading order.
    pub children: Vec<Bookmark>,
}

impl Bookmark {
    /// A leaf bookmark: `title` targeting `page`, with no children.
    pub fn new(title: impl Into<String>, page: usize) -> Bookmark {
        Bookmark {
            title: title.into(),
            page,
            children: Vec::new(),
        }
    }
}

/// A document-level attachment, embedded via the catalog's `/Names
/// /EmbeddedFiles` name tree (ISO 32000 §7.11.4). Unlike a page's painted
/// content, an attachment carries no rendering — only the bytes and the
/// metadata a viewer shows about them.
#[derive(Debug, Clone, PartialEq)]
pub struct Attachment {
    /// The file name: written as both the filespec's `/F` and `/UF`, and
    /// as the name-tree key.
    pub name: String,
    /// The attachment's raw bytes, stored as the embedded-file stream
    /// (compressed like any other stream, per [`WriteOptions::compress`]).
    pub data: Vec<u8>,
    /// MIME type, written as the embedded-file stream's `/Subtype`.
    /// `None` writes `application/octet-stream`.
    pub mime: Option<String>,
    /// `/Params /ModDate`, written only when given.
    pub modified: Option<Date>,
    /// `/Desc` on the filespec, written only when given.
    pub description: Option<String>,
}

/// A page-numbering style for a [`PageLabel`] range, written as its `/S`
/// (ISO 32000 §12.4.2, Table 159).
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum LabelStyle {
    /// Arabic numerals: 1, 2, 3…
    Decimal,
    /// Uppercase Roman numerals: I, II, III…
    RomanUpper,
    /// Lowercase Roman numerals: i, ii, iii…
    RomanLower,
    /// Uppercase letters: A, B, …, Z, AA…
    LettersUpper,
    /// Lowercase letters: a, b, …, z, aa…
    LettersLower,
}

/// One page-numbering range, taking effect from `first_page` (0-based)
/// until the next range's `first_page` or the document's end (ISO 32000
/// §12.4.2). A document's `page_labels` must include a range with
/// `first_page == 0` whenever it is non-empty.
#[derive(Debug, Clone, PartialEq)]
pub struct PageLabel {
    /// 0-based page index where this range begins.
    pub first_page: usize,
    /// Numbering style, written as `/S`; `None` omits it, showing only
    /// `prefix` for every page in the range.
    pub style: Option<LabelStyle>,
    /// Text prepended to every number in the range, written as `/P`.
    pub prefix: Option<String>,
    /// The number shown on `first_page`, written as `/St` only when not
    /// `1`. Conventionally `1`.
    pub start_at: u32,
}

/// Initial page-layout mode, written as the catalog's `/PageLayout` (ISO
/// 32000 §7.7.2, Table 27).
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum PageLayout {
    /// One page at a time.
    SinglePage,
    /// One continuously scrolling column of pages.
    OneColumn,
    /// Two columns, an odd-numbered page on the left.
    TwoColumnLeft,
    /// Two columns, an odd-numbered page on the right.
    TwoColumnRight,
    /// Two pages at a time, an odd-numbered page on the left.
    TwoPageLeft,
    /// Two pages at a time, an odd-numbered page on the right.
    TwoPageRight,
}

/// Initial navigation-panel mode, written as the catalog's `/PageMode`
/// (ISO 32000 §7.7.2, Table 28).
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum PageMode {
    /// No panel open.
    UseNone,
    /// The outline (bookmarks) panel.
    UseOutlines,
    /// The page-thumbnails panel.
    UseThumbs,
    /// Full-screen presentation mode.
    FullScreen,
}

/// Viewer preferences written to the catalog: initial layout, navigation
/// mode, and the page opened at document start (ISO 32000 §7.7.2).
#[derive(Debug, Clone, Default, PartialEq)]
pub struct Viewer {
    /// `/PageLayout`, omitted when `None`.
    pub layout: Option<PageLayout>,
    /// `/PageMode`, omitted when `None`.
    pub mode: Option<PageMode>,
    /// Page index opened via `/OpenAction`, keeping the viewer's current
    /// position and zoom, omitted when `None`.
    pub open_to: Option<usize>,
}

/// A document under construction. The fields are the composition:
/// singleton slots are `Option`s, pages keep the order given.
#[derive(Debug, Default)]
pub struct Pdf {
    /// Document information, if any.
    pub metadata: Option<Metadata>,
    /// Pages, in reading order.
    pub pages: Vec<Page>,
    /// Bookmark panel, if any.
    pub outline: Option<Outline>,
    /// Document-level attachments. Reordered by `name`, lexicographically
    /// by bytes, at emission — the name-tree keys must be sorted, so the
    /// order given here is not preserved. Duplicate names are an error.
    pub attachments: Vec<Attachment>,
    /// Page-numbering ranges shown in viewer UI as `/PageLabels`.
    /// Reordered by `first_page` at emission. Must include a range
    /// starting at page 0 when non-empty; duplicate `first_page` values
    /// are an error.
    pub page_labels: Vec<PageLabel>,
    /// Viewer preferences, if any.
    pub viewer: Option<Viewer>,
    /// File-emission options.
    pub options: WriteOptions,
}

impl Pdf {
    /// Serializes the document to complete PDF file bytes.
    ///
    /// Fonts are shared document-wide: each distinct [`Standard14`] face
    /// gets one font object, in first-use order. Images are embedded per
    /// page with no cross-page deduplication — the same raster drawn on
    /// two pages is stored twice. Groups follow the same rule: a canvas
    /// registered with `Canvas::group` on two different pages produces two
    /// Form XObjects — cross-page group sharing is deferred.
    pub fn to_bytes(self) -> Result<Vec<u8>> {
        let (w, root) = self.assemble()?;
        w.finish(root)
    }

    /// [`Pdf::to_bytes`] streaming into a [`std::io::Write`]: the same
    /// bytes, delivered in bounded chunks instead of one buffer. Unlike
    /// `to_bytes`, an error can leave a prefix of the file already written
    /// to `out`. No flush is performed.
    pub fn write_into(self, out: impl std::io::Write) -> Result<()> {
        let (w, root) = self.assemble()?;
        w.finish_into(root, out)
    }

    /// [`Pdf::to_bytes`] streaming into any [`AsyncByteSink`] — the
    /// asynchronous twin of [`Pdf::write_into`]. An error can leave a
    /// prefix of the file already written. Hands the sink back unflushed.
    pub async fn write_into_with<S: AsyncByteSink>(self, sink: S) -> Result<S> {
        let (w, root) = self.assemble()?;
        w.finish_into_with(root, sink).await
    }

    /// Builds the writer every write path finishes: all objects placed,
    /// the catalog's reference returned alongside.
    fn assemble(self) -> Result<(Writer, ObjRef)> {
        let Pdf {
            metadata,
            pages,
            outline,
            attachments,
            page_labels,
            viewer,
            options,
        } = self;
        if pages.is_empty() {
            return Err(Error::Other(
                "a document needs at least one page".to_string(),
            ));
        }
        let mut w = Writer::new(options);
        let pages_root = w.reserve();
        let page_count = pages.len();
        let page_refs: Vec<ObjRef> = pages.iter().map(|_| w.reserve()).collect();
        let mut font_cache: Vec<(Standard14, ObjRef)> = Vec::new();
        for (index, page) in pages.into_iter().enumerate() {
            let Page {
                size,
                rotation,
                mut canvas,
                content,
                mut links,
            } = page;
            if rotation % 90 != 0 {
                return Err(Error::Other(format!(
                    "page rotation {rotation} is not a multiple of 90"
                )));
            }
            element::lower(content, &mut canvas, &mut links)?;
            let (width, height) = size.dimensions();
            let parts = canvas.into_parts();
            let content_ref = w.put_stream(Dict::new(), serialize_ops(&parts.ops));
            let mut fonts = Dict::new();
            for (index, face) in parts.fonts.iter().enumerate() {
                let font_ref = cached_font(&mut w, &mut font_cache, face);
                fonts.insert(Name(format!("F{}", index + 1)), Object::Ref(font_ref));
            }
            let mut xobjects = Dict::new();
            for (index, image) in parts.images.iter().enumerate() {
                let image_ref = image.build_xobject(&mut w);
                xobjects.insert(Name(format!("Im{}", index + 1)), Object::Ref(image_ref));
            }
            for (index, (group_parts, bbox)) in parts.groups.into_iter().enumerate() {
                let group_ref = build_form(&mut w, group_parts, bbox, &mut font_cache)?;
                xobjects.insert(Name(format!("Gp{}", index + 1)), Object::Ref(group_ref));
            }
            let mut ext_gstates = Dict::new();
            for (index, state) in parts.gstates.iter().enumerate() {
                let gstate_ref = w.put(Object::Dict(state.ext_gstate_dict()));
                ext_gstates.insert(Name(format!("Gs{}", index + 1)), Object::Ref(gstate_ref));
            }
            let mut resources = Dict::new();
            if !fonts.is_empty() {
                resources.insert(name("Font"), Object::Dict(fonts));
            }
            if !xobjects.is_empty() {
                resources.insert(name("XObject"), Object::Dict(xobjects));
            }
            if !ext_gstates.is_empty() {
                resources.insert(name("ExtGState"), Object::Dict(ext_gstates));
            }
            let mut dict = Dict::new();
            dict.insert(name("Type"), Object::Name(name("Page")));
            dict.insert(name("Parent"), Object::Ref(pages_root));
            dict.insert(
                name("MediaBox"),
                Object::Array(vec![
                    Object::Int(0),
                    Object::Int(0),
                    Object::Real(f64::from(width)),
                    Object::Real(f64::from(height)),
                ]),
            );
            dict.insert(name("Contents"), Object::Ref(content_ref));
            dict.insert(name("Resources"), Object::Dict(resources));
            if !links.is_empty() {
                let mut annots = Vec::with_capacity(links.len());
                for link in links {
                    let action = match link.target {
                        LinkTarget::Uri(uri) => {
                            let mut action = Dict::new();
                            action.insert(name("S"), Object::Name(name("URI")));
                            action.insert(name("URI"), text_string(&uri));
                            action
                        }
                        LinkTarget::Page(target_index) => {
                            let target = page_refs.get(target_index).copied().ok_or_else(|| {
                                Error::Other(format!(
                                    "link target page {target_index} is out of range: the document has {page_count} pages"
                                ))
                            })?;
                            let mut action = Dict::new();
                            action.insert(name("S"), Object::Name(name("GoTo")));
                            action.insert(
                                name("D"),
                                Object::Array(vec![
                                    Object::Ref(target),
                                    Object::Name(name("XYZ")),
                                    Object::Null,
                                    Object::Null,
                                    Object::Null,
                                ]),
                            );
                            action
                        }
                    };
                    let mut annot = Dict::new();
                    annot.insert(name("Type"), Object::Name(name("Annot")));
                    annot.insert(name("Subtype"), Object::Name(name("Link")));
                    annot.insert(
                        name("Rect"),
                        Object::Array(
                            link.rect
                                .iter()
                                .map(|v| Object::Real(f64::from(*v)))
                                .collect(),
                        ),
                    );
                    annot.insert(
                        name("Border"),
                        Object::Array(vec![Object::Int(0), Object::Int(0), Object::Int(0)]),
                    );
                    annot.insert(name("A"), Object::Dict(action));
                    annots.push(Object::Ref(w.put(Object::Dict(annot))));
                }
                dict.insert(name("Annots"), Object::Array(annots));
            }
            if rotation != 0 {
                dict.insert(name("Rotate"), Object::Int(i64::from(rotation)));
            }
            w.fill(page_refs[index], Object::Dict(dict))?;
        }
        let kids: Vec<Object> = page_refs.iter().copied().map(Object::Ref).collect();
        let mut tree = Dict::new();
        tree.insert(name("Type"), Object::Name(name("Pages")));
        tree.insert(name("Count"), Object::Int(kids.len() as i64));
        tree.insert(name("Kids"), Object::Array(kids));
        w.fill(pages_root, Object::Dict(tree))?;
        let xmp_ref = match metadata {
            Some(meta) => {
                let packet = crate::xmp::packet(&meta);
                if let Some(info) = info_dict(meta) {
                    let info_ref = w.put(Object::Dict(info));
                    w.set_info(info_ref);
                }
                let mut xmp_dict = Dict::new();
                xmp_dict.insert(name("Type"), Object::Name(name("Metadata")));
                xmp_dict.insert(name("Subtype"), Object::Name(name("XML")));
                Some(w.put_stream_raw(xmp_dict, packet))
            }
            None => None,
        };
        let outline_ref = match outline {
            Some(outline) if !outline.bookmarks.is_empty() => {
                let root_ref = w.reserve();
                let refs = reserve_bookmarks(&mut w, &outline.bookmarks);
                let (first, last, count) = fill_bookmarks(
                    &mut w,
                    outline.bookmarks,
                    &refs,
                    root_ref,
                    &page_refs,
                    page_count,
                )?;
                let mut dict = Dict::new();
                dict.insert(name("Type"), Object::Name(name("Outlines")));
                dict.insert(name("First"), Object::Ref(first));
                dict.insert(name("Last"), Object::Ref(last));
                dict.insert(name("Count"), Object::Int(count));
                w.fill(root_ref, Object::Dict(dict))?;
                Some(root_ref)
            }
            _ => None,
        };
        let names = embedded_files_dict(&mut w, attachments)?;
        let page_labels_entry = page_labels_dict(page_labels)?;
        let mut catalog = Dict::new();
        catalog.insert(name("Type"), Object::Name(name("Catalog")));
        catalog.insert(name("Pages"), Object::Ref(pages_root));
        if let Some(outline_ref) = outline_ref {
            catalog.insert(name("Outlines"), Object::Ref(outline_ref));
        }
        if let Some(xmp_ref) = xmp_ref {
            catalog.insert(name("Metadata"), Object::Ref(xmp_ref));
        }
        if let Some(names) = names {
            catalog.insert(name("Names"), Object::Dict(names));
        }
        if let Some(page_labels_entry) = page_labels_entry {
            catalog.insert(name("PageLabels"), Object::Dict(page_labels_entry));
        }
        if let Some(viewer) = viewer {
            let Viewer {
                layout,
                mode,
                open_to,
            } = viewer;
            if let Some(layout) = layout {
                catalog.insert(
                    name("PageLayout"),
                    Object::Name(name(page_layout_name(layout))),
                );
            }
            if let Some(mode) = mode {
                catalog.insert(name("PageMode"), Object::Name(name(page_mode_name(mode))));
            }
            if let Some(open_to) = open_to {
                let target = page_refs.get(open_to).copied().ok_or_else(|| {
                    Error::Other(format!(
                        "open_to target page {open_to} is out of range: the document has {page_count} pages"
                    ))
                })?;
                catalog.insert(
                    name("OpenAction"),
                    Object::Array(vec![
                        Object::Ref(target),
                        Object::Name(name("XYZ")),
                        Object::Null,
                        Object::Null,
                        Object::Null,
                    ]),
                );
            }
        }
        let root = w.put(Object::Dict(catalog));
        Ok((w, root))
    }

    /// Serializes and writes the document to `path`.
    pub fn save(self, path: impl AsRef<Path>) -> Result<()> {
        let path = path.as_ref();
        let bytes = self.to_bytes()?;
        std::fs::write(path, bytes)?;
        Ok(())
    }
}

/// A `Name` from a string literal.
fn name(text: &str) -> Name {
    Name(text.to_string())
}

/// Builds the `/Info` dictionary, or `None` when every field is `None`.
fn info_dict(meta: Metadata) -> Option<Dict> {
    let mut dict = Dict::new();
    let texts = [
        ("Title", meta.title),
        ("Author", meta.author),
        ("Subject", meta.subject),
        ("Keywords", meta.keywords),
        ("Creator", meta.creator),
        ("Producer", meta.producer),
    ];
    for (key, value) in texts {
        if let Some(value) = value {
            dict.insert(name(key), text_string(&value));
        }
    }
    let dates = [
        ("CreationDate", meta.creation_date),
        ("ModDate", meta.modification_date),
    ];
    for (key, value) in dates {
        if let Some(date) = value {
            dict.insert(name(key), Object::String(date.to_pdf_string().into_bytes()));
        }
    }
    if dict.is_empty() {
        return None;
    }
    Some(dict)
}

/// Default MIME type for an [`Attachment`] whose `mime` is `None`.
const DEFAULT_ATTACHMENT_MIME: &str = "application/octet-stream";

/// Builds the catalog's `/Names` dictionary from `attachments`, or `None`
/// when there are none. Attachments are reordered by `name`, bytewise, to
/// satisfy the name tree's sorted-key requirement — string comparison in
/// Rust is already a byte comparison, so sorting `String` values sorts
/// their bytes. A repeated name is an error naming the duplicate.
fn embedded_files_dict(w: &mut Writer, mut attachments: Vec<Attachment>) -> Result<Option<Dict>> {
    if attachments.is_empty() {
        return Ok(None);
    }
    attachments.sort_by(|a, b| a.name.cmp(&b.name));
    for pair in attachments.windows(2) {
        if pair[0].name == pair[1].name {
            return Err(Error::Other(format!(
                "duplicate attachment name: {:?}",
                pair[0].name
            )));
        }
    }
    let mut entries = Vec::with_capacity(attachments.len() * 2);
    for attachment in attachments {
        let Attachment {
            name: file_name,
            data,
            mime,
            modified,
            description,
        } = attachment;
        let mime = mime.unwrap_or_else(|| DEFAULT_ATTACHMENT_MIME.to_string());

        let mut params = Dict::new();
        params.insert(name("Size"), Object::Int(data.len() as i64));
        if let Some(modified) = modified {
            params.insert(
                name("ModDate"),
                Object::String(modified.to_pdf_string().into_bytes()),
            );
        }
        let mut stream_dict = Dict::new();
        stream_dict.insert(name("Type"), Object::Name(name("EmbeddedFile")));
        stream_dict.insert(name("Subtype"), Object::Name(Name(mime)));
        stream_dict.insert(name("Params"), Object::Dict(params));
        let stream_ref = w.put_stream(stream_dict, data);

        let mut ef = Dict::new();
        ef.insert(name("F"), Object::Ref(stream_ref));

        let mut filespec = Dict::new();
        filespec.insert(name("Type"), Object::Name(name("Filespec")));
        filespec.insert(name("F"), text_string(&file_name));
        filespec.insert(name("UF"), text_string(&file_name));
        if let Some(description) = description {
            filespec.insert(name("Desc"), text_string(&description));
        }
        filespec.insert(name("EF"), Object::Dict(ef));
        let filespec_ref = w.put(Object::Dict(filespec));

        entries.push(text_string(&file_name));
        entries.push(Object::Ref(filespec_ref));
    }
    let mut name_tree = Dict::new();
    name_tree.insert(name("Names"), Object::Array(entries));
    let mut embedded_files = Dict::new();
    embedded_files.insert(name("EmbeddedFiles"), Object::Dict(name_tree));
    Ok(Some(embedded_files))
}

/// Builds the catalog's `/PageLabels` dictionary from `labels`, or `None`
/// when there are none. Ranges are reordered by `first_page` to satisfy
/// the number tree's sorted-key requirement. A non-empty set must include
/// a range starting at page 0; a repeated `first_page` is an error naming
/// the page; a `start_at` of 0 is an error naming the page, since ISO
/// 32000 page-label numbering starts at 1.
fn page_labels_dict(mut labels: Vec<PageLabel>) -> Result<Option<Dict>> {
    if labels.is_empty() {
        return Ok(None);
    }
    for label in &labels {
        if label.start_at == 0 {
            return Err(Error::Other(format!(
                "page label at page {} has start_at 0: numbering starts at 1",
                label.first_page
            )));
        }
    }
    labels.sort_by_key(|label| label.first_page);
    if labels[0].first_page != 0 {
        return Err(Error::Other("page labels must start at page 0".to_string()));
    }
    for pair in labels.windows(2) {
        if pair[0].first_page == pair[1].first_page {
            return Err(Error::Other(format!(
                "duplicate page label at page {}",
                pair[0].first_page
            )));
        }
    }
    let mut nums = Vec::with_capacity(labels.len() * 2);
    for label in labels {
        let PageLabel {
            first_page,
            style,
            prefix,
            start_at,
        } = label;
        let mut range = Dict::new();
        if let Some(style) = style {
            range.insert(name("S"), Object::Name(name(label_style_name(style))));
        }
        if let Some(prefix) = prefix {
            range.insert(name("P"), text_string(&prefix));
        }
        if start_at != 1 {
            range.insert(name("St"), Object::Int(i64::from(start_at)));
        }
        nums.push(Object::Int(first_page as i64));
        nums.push(Object::Dict(range));
    }
    let mut dict = Dict::new();
    dict.insert(name("Nums"), Object::Array(nums));
    Ok(Some(dict))
}

/// The `/S` name for a [`LabelStyle`].
fn label_style_name(style: LabelStyle) -> &'static str {
    match style {
        LabelStyle::Decimal => "D",
        LabelStyle::RomanUpper => "R",
        LabelStyle::RomanLower => "r",
        LabelStyle::LettersUpper => "A",
        LabelStyle::LettersLower => "a",
    }
}

/// The `/PageLayout` name for a [`PageLayout`].
fn page_layout_name(layout: PageLayout) -> &'static str {
    match layout {
        PageLayout::SinglePage => "SinglePage",
        PageLayout::OneColumn => "OneColumn",
        PageLayout::TwoColumnLeft => "TwoColumnLeft",
        PageLayout::TwoColumnRight => "TwoColumnRight",
        PageLayout::TwoPageLeft => "TwoPageLeft",
        PageLayout::TwoPageRight => "TwoPageRight",
    }
}

/// The `/PageMode` name for a [`PageMode`].
fn page_mode_name(mode: PageMode) -> &'static str {
    match mode {
        PageMode::UseNone => "UseNone",
        PageMode::UseOutlines => "UseOutlines",
        PageMode::UseThumbs => "UseThumbs",
        PageMode::FullScreen => "FullScreen",
    }
}

/// One bookmark's reserved object number, mirroring the tree shape so the
/// fill pass can wire parent, sibling and child refs before any of their
/// dictionary bodies exist.
struct BookmarkRef {
    r: ObjRef,
    children: Vec<BookmarkRef>,
}

/// Reserves an object number for every node in `bookmarks`, recursively —
/// the reserve half of the reserve/fill idiom: an outline item's `/Parent`,
/// `/Prev`, `/Next`, `/First` and `/Last` may all point at nodes that do
/// not have a body yet.
fn reserve_bookmarks(w: &mut Writer, bookmarks: &[Bookmark]) -> Vec<BookmarkRef> {
    bookmarks
        .iter()
        .map(|bookmark| BookmarkRef {
            r: w.reserve(),
            children: reserve_bookmarks(w, &bookmark.children),
        })
        .collect()
}

/// Fills one sibling chain of outline items against their already-reserved
/// refs: `/Title`, `/Parent`, the `/Prev`/`/Next` chain, `/Dest`, and — for
/// any bookmark with children — `/First`/`/Last`/`/Count` from a recursive
/// fill of that subtree. Returns the chain's first and last refs and the
/// total number of items in the whole subtree, which doubles as `/Count`
/// wherever the caller needs it (every bookmark is open).
fn fill_bookmarks(
    w: &mut Writer,
    bookmarks: Vec<Bookmark>,
    refs: &[BookmarkRef],
    parent: ObjRef,
    page_refs: &[ObjRef],
    page_count: usize,
) -> Result<(ObjRef, ObjRef, i64)> {
    let last_index = bookmarks.len() - 1;
    let mut total = 0i64;
    for (index, bookmark) in bookmarks.into_iter().enumerate() {
        let Bookmark {
            title,
            page,
            children,
        } = bookmark;
        let dest = page_refs.get(page).copied().ok_or_else(|| {
            Error::Other(format!(
                "bookmark target page {page} is out of range: the document has {page_count} pages"
            ))
        })?;
        let mut dict = Dict::new();
        dict.insert(name("Title"), text_string(&title));
        dict.insert(name("Parent"), Object::Ref(parent));
        if index > 0 {
            dict.insert(name("Prev"), Object::Ref(refs[index - 1].r));
        }
        if index < last_index {
            dict.insert(name("Next"), Object::Ref(refs[index + 1].r));
        }
        dict.insert(
            name("Dest"),
            Object::Array(vec![
                Object::Ref(dest),
                Object::Name(name("XYZ")),
                Object::Null,
                Object::Null,
                Object::Null,
            ]),
        );
        let mut subtree_count = 0i64;
        if !children.is_empty() {
            let (first, last, count) = fill_bookmarks(
                w,
                children,
                &refs[index].children,
                refs[index].r,
                page_refs,
                page_count,
            )?;
            dict.insert(name("First"), Object::Ref(first));
            dict.insert(name("Last"), Object::Ref(last));
            dict.insert(name("Count"), Object::Int(count));
            subtree_count = count;
        }
        w.fill(refs[index].r, Object::Dict(dict))?;
        total += 1 + subtree_count;
    }
    Ok((refs[0].r, refs[last_index].r, total))
}

/// The document-wide font object for `face`: an existing entry from
/// `font_cache` when one matches, otherwise a freshly built one that is
/// cached for the next lookup. Shared by the page loop and every nested
/// [`build_form`] so a face used both on a page and inside a group still
/// gets exactly one font object.
fn cached_font(
    w: &mut Writer,
    font_cache: &mut Vec<(Standard14, ObjRef)>,
    face: &Standard14,
) -> ObjRef {
    if let Some((_, r)) = font_cache.iter().find(|(seen, _)| seen == face) {
        return *r;
    }
    let r = w.put(Object::Dict(face.font_dict()));
    font_cache.push((*face, r));
    r
}

/// Builds one Form XObject from a registered group's parts: `/Type
/// /XObject /Subtype /Form /BBox /Resources`, with the sub-canvas's
/// operators as its content stream. Recurses for groups nested inside
/// groups, and shares `font_cache` with the page loop so nested forms
/// never duplicate a font already emitted elsewhere in the document.
fn build_form(
    w: &mut Writer,
    parts: CanvasParts,
    bbox: [f32; 4],
    font_cache: &mut Vec<(Standard14, ObjRef)>,
) -> Result<ObjRef> {
    let content = serialize_ops(&parts.ops);
    let mut fonts = Dict::new();
    for (index, face) in parts.fonts.iter().enumerate() {
        let font_ref = cached_font(w, font_cache, face);
        fonts.insert(Name(format!("F{}", index + 1)), Object::Ref(font_ref));
    }
    let mut xobjects = Dict::new();
    for (index, image) in parts.images.iter().enumerate() {
        let image_ref = image.build_xobject(w);
        xobjects.insert(Name(format!("Im{}", index + 1)), Object::Ref(image_ref));
    }
    for (index, (group_parts, group_bbox)) in parts.groups.into_iter().enumerate() {
        let group_ref = build_form(w, group_parts, group_bbox, font_cache)?;
        xobjects.insert(Name(format!("Gp{}", index + 1)), Object::Ref(group_ref));
    }
    let mut ext_gstates = Dict::new();
    for (index, state) in parts.gstates.iter().enumerate() {
        let gstate_ref = w.put(Object::Dict(state.ext_gstate_dict()));
        ext_gstates.insert(Name(format!("Gs{}", index + 1)), Object::Ref(gstate_ref));
    }
    let mut resources = Dict::new();
    if !fonts.is_empty() {
        resources.insert(name("Font"), Object::Dict(fonts));
    }
    if !xobjects.is_empty() {
        resources.insert(name("XObject"), Object::Dict(xobjects));
    }
    if !ext_gstates.is_empty() {
        resources.insert(name("ExtGState"), Object::Dict(ext_gstates));
    }
    let mut dict = Dict::new();
    dict.insert(name("Type"), Object::Name(name("XObject")));
    dict.insert(name("Subtype"), Object::Name(name("Form")));
    dict.insert(
        name("BBox"),
        Object::Array(bbox.iter().map(|v| Object::Real(f64::from(*v))).collect()),
    );
    dict.insert(name("Resources"), Object::Dict(resources));
    Ok(w.put_stream(dict, content))
}

/// Encodes a text string (ISO 32000 §7.9.2.2): pure ASCII passes through
/// as its own bytes, anything else becomes UTF-16BE with a `FE FF` byte
/// order mark.
fn text_string(value: &str) -> Object {
    if value.is_ascii() {
        return Object::String(value.as_bytes().to_vec());
    }
    let mut bytes = vec![0xFE, 0xFF];
    for unit in value.encode_utf16() {
        bytes.extend_from_slice(&unit.to_be_bytes());
    }
    Object::String(bytes)
}

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

    #[test]
    fn dimensions_match_the_contract() {
        assert_eq!(PageSize::A3.dimensions(), (841.89, 1190.55));
        assert_eq!(PageSize::A4.dimensions(), (595.28, 841.89));
        assert_eq!(PageSize::A5.dimensions(), (419.53, 595.28));
        assert_eq!(PageSize::Letter.dimensions(), (612.0, 792.0));
        assert_eq!(PageSize::Legal.dimensions(), (612.0, 1008.0));
        assert_eq!(
            PageSize::Custom {
                width: 10.0,
                height: 20.0
            }
            .dimensions(),
            (10.0, 20.0)
        );
    }

    #[test]
    fn by_name_parses_the_five_named_sizes_case_insensitively() {
        for (name, expected) in [
            ("a3", PageSize::A3),
            ("A4", PageSize::A4),
            ("a5", PageSize::A5),
            ("Letter", PageSize::Letter),
            ("LEGAL", PageSize::Legal),
        ] {
            assert_eq!(PageSize::by_name(name), Some(expected), "{name}");
        }
    }

    #[test]
    fn by_name_rejects_anything_else() {
        assert_eq!(PageSize::by_name("tabloid"), None);
        assert_eq!(PageSize::by_name(""), None);
    }

    #[test]
    fn landscape_swaps_into_custom() {
        assert_eq!(
            PageSize::A4.landscape(),
            PageSize::Custom {
                width: 841.89,
                height: 595.28
            }
        );
        assert_eq!(
            PageSize::Custom {
                width: 1.0,
                height: 2.0
            }
            .landscape(),
            PageSize::Custom {
                width: 2.0,
                height: 1.0
            }
        );
        assert_eq!(PageSize::Letter.landscape().dimensions(), (792.0, 612.0));
    }

    #[test]
    fn date_utc_formats_with_z() {
        let date = Date {
            year: 2026,
            month: 8,
            day: 27,
            hour: 12,
            minute: 30,
            second: 15,
            utc_offset_minutes: 0,
        };
        assert_eq!(date.to_pdf_string(), "D:20260827123015Z");
    }

    #[test]
    fn date_positive_offset_pads_single_digits() {
        let date = Date {
            year: 987,
            month: 1,
            day: 2,
            hour: 3,
            minute: 4,
            second: 5,
            utc_offset_minutes: 120,
        };
        assert_eq!(date.to_pdf_string(), "D:09870102030405+02'00");
    }

    #[test]
    fn date_negative_offset_keeps_minutes() {
        let date = Date {
            year: 1999,
            month: 12,
            day: 31,
            hour: 23,
            minute: 59,
            second: 58,
            utc_offset_minutes: -330,
        };
        assert_eq!(date.to_pdf_string(), "D:19991231235958-05'30");
    }

    #[test]
    fn iso8601_utc_formats_with_z() {
        let date = Date {
            year: 2026,
            month: 8,
            day: 27,
            hour: 12,
            minute: 30,
            second: 15,
            utc_offset_minutes: 0,
        };
        assert_eq!(date.to_iso8601(), "2026-08-27T12:30:15Z");
    }

    #[test]
    fn iso8601_positive_offset_pads_single_digits() {
        let date = Date {
            year: 987,
            month: 1,
            day: 2,
            hour: 3,
            minute: 4,
            second: 5,
            utc_offset_minutes: 120,
        };
        assert_eq!(date.to_iso8601(), "0987-01-02T03:04:05+02:00");
    }

    #[test]
    fn iso8601_negative_offset_keeps_minutes() {
        let date = Date {
            year: 1999,
            month: 12,
            day: 31,
            hour: 23,
            minute: 59,
            second: 58,
            utc_offset_minutes: -330,
        };
        assert_eq!(date.to_iso8601(), "1999-12-31T23:59:58-05:30");
    }

    /// Two pages with text and an image — enough to exercise fonts,
    /// XObjects and the reserved page tree through every write path.
    fn two_page_doc() -> Pdf {
        let mut first = Page::new(PageSize::A4);
        first
            .canvas
            .text("Streamed parity", 72.0, 720.0, Standard14::Helvetica, 14.0)
            .expect("ASCII encodes");
        let image = crate::image::ImageData::gray8(2, 2, vec![0, 85, 170, 255])
            .expect("2x2 grayscale builds");
        let handle = first.canvas.add_image(image);
        first.canvas.draw_image(handle, 72.0, 400.0, 144.0, 144.0);
        let mut second = Page::new(PageSize::Letter);
        second
            .canvas
            .text("Page two", 72.0, 700.0, Standard14::TimesRoman, 12.0)
            .expect("ASCII encodes");
        Pdf {
            pages: vec![first, second],
            ..Pdf::default()
        }
    }

    /// The three write paths are one assembly and one emission: identical
    /// bytes whether buffered, streamed into an `io::Write`, or streamed
    /// into an async sink.
    #[test]
    fn write_into_and_write_into_with_match_to_bytes() {
        let bytes = two_page_doc().to_bytes().expect("to_bytes succeeds");
        let mut via_io = Vec::new();
        two_page_doc()
            .write_into(&mut via_io)
            .expect("write_into succeeds");
        assert_eq!(via_io, bytes);
        let via_sink = pdfboss_core::block_on(two_page_doc().write_into_with(Vec::new()))
            .expect("write_into_with succeeds");
        assert_eq!(via_sink, bytes);
    }

    #[test]
    fn zero_page_document_is_an_error() {
        let err = Pdf::default()
            .to_bytes()
            .expect_err("a page-less document must not serialize");
        assert!(err.to_string().contains("at least one page"), "{err}");
    }
}