//! Native OpenDocument Text (.odt) generation from markdown.
//!
//! An .odt file is a ZIP archive containing (at minimum):
//!   * `mimetype`            - the media type, stored uncompressed and first
//!   * `META-INF/manifest.xml` - lists the archive members
//!   * `styles.xml`          - named paragraph / text / list styles
//!   * `content.xml`         - the document body
//!
//! We parse each markdown document with pulldown-cmark and emit ODF flow
//! elements. Each source file becomes a chapter: a "Heading 1" with the chapter
//! title, followed by the converted body (whose own headings are shifted down a
//! level so they nest under the chapter heading).

use pulldown_cmark::{CodeBlockKind, Event, HeadingLevel, Options, Parser, Tag, TagEnd};
use std::io::Write;
use std::path::Path;
use zip::write::SimpleFileOptions;

/// One chapter to export.
pub struct Chapter {
    pub title: String,
    /// Optional caption shown beneath the chapter title (from the `# Slug:` line).
    pub slug: Option<String>,
    pub markdown: String,
}

/// Escape text for use inside XML character data.
fn esc(s: &str) -> String {
    let mut out = String::with_capacity(s.len());
    for c in s.chars() {
        match c {
            '&' => out.push_str("&amp;"),
            '<' => out.push_str("&lt;"),
            '>' => out.push_str("&gt;"),
            _ => out.push(c),
        }
    }
    out
}

/// Escape text for use inside an XML attribute value.
fn esc_attr(s: &str) -> String {
    let mut out = esc(s);
    out = out.replace('"', "&quot;");
    out
}

/// Which block-level element is currently open in the output stream.
#[derive(PartialEq, Clone, Copy)]
enum Block {
    None,
    Para,
    Heading(u8),
}

struct Converter {
    out: String,
    block: Block,
    bold: bool,
    italic: bool,
    strike: bool,
    code: bool,
    link: Option<String>,
    /// Stack of list markers: true = ordered, false = unordered.
    list_stack: Vec<bool>,
    /// True while inside a blockquote (affects paragraph style).
    quote_depth: u32,
    /// Buffer collecting the text of the current code block.
    code_block: Option<String>,
    /// Heading level offset so document headings nest under the chapter title.
    heading_offset: u8,
}

impl Converter {
    fn new(heading_offset: u8) -> Self {
        Converter {
            out: String::new(),
            block: Block::None,
            bold: false,
            italic: false,
            strike: false,
            code: false,
            link: None,
            list_stack: Vec::new(),
            quote_depth: 0,
            code_block: None,
            heading_offset,
        }
    }

    fn para_style(&self) -> &'static str {
        if self.quote_depth > 0 {
            "Quotations"
        } else {
            "Text_20_body"
        }
    }

    /// Ensure a block-level element is open to receive inline content.
    fn ensure_inline_target(&mut self) {
        if self.block == Block::None {
            let style = self.para_style();
            self.out
                .push_str(&format!("<text:p text:style-name=\"{style}\">"));
            self.block = Block::Para;
        }
    }

    fn close_block(&mut self) {
        match self.block {
            Block::Para => self.out.push_str("</text:p>"),
            Block::Heading(_) => self.out.push_str("</text:h>"),
            Block::None => {}
        }
        self.block = Block::None;
    }

    /// Emit an inline text run with the currently active character formatting.
    fn write_text(&mut self, text: &str) {
        self.ensure_inline_target();
        let escaped = esc(text);

        // Choose a text (character) style for the active emphasis flags.
        let span_style = if self.code {
            Some("Source_20_Text")
        } else {
            match (self.bold, self.italic, self.strike) {
                (true, true, _) => Some("T_bolditalic"),
                (true, false, false) => Some("T_bold"),
                (false, true, false) => Some("T_italic"),
                (_, _, true) => Some("T_strike"),
                _ => None,
            }
        };

        let mut run = String::new();
        if let Some(style) = span_style {
            run.push_str(&format!("<text:span text:style-name=\"{style}\">"));
            run.push_str(&escaped);
            run.push_str("</text:span>");
        } else {
            run.push_str(&escaped);
        }

        if let Some(href) = &self.link {
            self.out.push_str(&format!(
                "<text:a xlink:type=\"simple\" xlink:href=\"{}\">{run}</text:a>",
                esc_attr(href)
            ));
        } else {
            self.out.push_str(&run);
        }
    }

    fn start_list(&mut self, ordered: bool) {
        self.close_block();
        let style = if ordered { "L_number" } else { "L_bullet" };
        self.out
            .push_str(&format!("<text:list text:style-name=\"{style}\">"));
        self.list_stack.push(ordered);
    }

    fn end_list(&mut self) {
        self.close_block();
        self.out.push_str("</text:list>");
        self.list_stack.pop();
    }

    fn flush_code_block(&mut self) {
        if let Some(buf) = self.code_block.take() {
            // Trailing newline from the fenced block is not a real line.
            let content = buf.strip_suffix('\n').unwrap_or(&buf);
            for line in content.split('\n') {
                self.out
                    .push_str("<text:p text:style-name=\"Preformatted_Text\">");
                self.write_preformatted_line(line);
                self.out.push_str("</text:p>");
            }
        }
    }

    /// Write a single code line, preserving runs of spaces and tabs.
    fn write_preformatted_line(&mut self, line: &str) {
        let mut chars = line.chars().peekable();
        while let Some(c) = chars.next() {
            match c {
                ' ' => {
                    let mut count = 1;
                    while chars.peek() == Some(&' ') {
                        chars.next();
                        count += 1;
                    }
                    if count == 1 {
                        self.out.push(' ');
                    } else {
                        self.out
                            .push_str(&format!("<text:s text:c=\"{count}\"/>"));
                    }
                }
                '\t' => self.out.push_str("<text:tab/>"),
                '&' => self.out.push_str("&amp;"),
                '<' => self.out.push_str("&lt;"),
                '>' => self.out.push_str("&gt;"),
                _ => self.out.push(c),
            }
        }
    }

    fn heading_number(&self, level: HeadingLevel) -> u8 {
        let base = match level {
            HeadingLevel::H1 => 1,
            HeadingLevel::H2 => 2,
            HeadingLevel::H3 => 3,
            HeadingLevel::H4 => 4,
            HeadingLevel::H5 => 5,
            HeadingLevel::H6 => 6,
        };
        (base + self.heading_offset).min(10)
    }

    fn run(mut self, markdown: &str) -> String {
        let mut opts = Options::empty();
        opts.insert(Options::ENABLE_STRIKETHROUGH);
        let parser = Parser::new_ext(markdown, opts);

        for event in parser {
            match event {
                Event::Start(tag) => self.start_tag(tag),
                Event::End(tag) => self.end_tag(tag),
                Event::Text(t) => {
                    if let Some(buf) = self.code_block.as_mut() {
                        buf.push_str(&t);
                    } else {
                        self.write_text(&t);
                    }
                }
                Event::Code(t) => {
                    self.code = true;
                    self.write_text(&t);
                    self.code = false;
                }
                Event::SoftBreak => {
                    if self.code_block.is_some() {
                        // handled via Text
                    } else {
                        self.write_text(" ");
                    }
                }
                Event::HardBreak => {
                    self.ensure_inline_target();
                    self.out.push_str("<text:line-break/>");
                }
                Event::Rule => {
                    self.close_block();
                    self.out
                        .push_str("<text:p text:style-name=\"Horizontal_Line\"></text:p>");
                }
                Event::Html(_) | Event::InlineHtml(_) => { /* skip raw HTML */ }
                _ => {}
            }
        }
        self.close_block();
        self.out
    }

    fn start_tag(&mut self, tag: Tag) {
        match tag {
            Tag::Paragraph => {
                // Lazily opened by the first inline content.
                self.close_block();
            }
            Tag::Heading { level, .. } => {
                self.close_block();
                let n = self.heading_number(level);
                self.out.push_str(&format!(
                    "<text:h text:style-name=\"Heading_20_{n}\" text:outline-level=\"{n}\">"
                ));
                self.block = Block::Heading(n);
            }
            Tag::BlockQuote(_) => {
                self.close_block();
                self.quote_depth += 1;
            }
            Tag::CodeBlock(kind) => {
                self.close_block();
                let _ = match kind {
                    CodeBlockKind::Fenced(_) => (),
                    CodeBlockKind::Indented => (),
                };
                self.code_block = Some(String::new());
            }
            Tag::List(first) => {
                self.start_list(first.is_some());
            }
            Tag::Item => {
                self.out.push_str("<text:list-item>");
            }
            Tag::Emphasis => self.italic = true,
            Tag::Strong => self.bold = true,
            Tag::Strikethrough => self.strike = true,
            Tag::Link { dest_url, .. } => {
                self.link = Some(dest_url.to_string());
            }
            Tag::Image { title, dest_url, .. } => {
                // We do not embed images; surface a readable placeholder.
                let label = if !title.is_empty() {
                    title.to_string()
                } else {
                    dest_url.to_string()
                };
                self.write_text(&format!("[image: {label}]"));
            }
            _ => {}
        }
    }

    fn end_tag(&mut self, tag: TagEnd) {
        match tag {
            TagEnd::Paragraph => self.close_block(),
            TagEnd::Heading(_) => self.close_block(),
            TagEnd::BlockQuote(_) => {
                self.close_block();
                if self.quote_depth > 0 {
                    self.quote_depth -= 1;
                }
            }
            TagEnd::CodeBlock => self.flush_code_block(),
            TagEnd::List(_) => self.end_list(),
            TagEnd::Item => {
                self.close_block();
                self.out.push_str("</text:list-item>");
            }
            TagEnd::Emphasis => self.italic = false,
            TagEnd::Strong => self.bold = false,
            TagEnd::Strikethrough => self.strike = false,
            TagEnd::Link => self.link = None,
            _ => {}
        }
    }
}

/// Convert one markdown document into an ODF body fragment, with headings shifted
/// down by `heading_offset` levels.
fn markdown_to_body(markdown: &str, heading_offset: u8) -> String {
    Converter::new(heading_offset).run(markdown)
}

const MIMETYPE: &str = "application/vnd.oasis.opendocument.text";

fn manifest_xml() -> String {
    r#"<?xml version="1.0" encoding="UTF-8"?>
<manifest:manifest xmlns:manifest="urn:oasis:names:tc:opendocument:xmlns:manifest:1.0" manifest:version="1.2">
 <manifest:file-entry manifest:full-path="/" manifest:media-type="application/vnd.oasis.opendocument.text"/>
 <manifest:file-entry manifest:full-path="content.xml" manifest:media-type="text/xml"/>
 <manifest:file-entry manifest:full-path="styles.xml" manifest:media-type="text/xml"/>
</manifest:manifest>"#
        .to_string()
}

fn styles_xml() -> String {
    // Heading sizes for the seven levels we may emit (chapter = 1).
    let sizes = [18, 16, 14, 13, 12, 11, 11, 11, 11, 11];
    let mut headings = String::new();
    for (i, size) in sizes.iter().enumerate() {
        let n = i + 1;
        headings.push_str(&format!(
            "<style:style style:name=\"Heading_20_{n}\" style:display-name=\"Heading {n}\" \
             style:family=\"paragraph\" style:parent-style-name=\"Heading\" \
             style:next-style-name=\"Text_20_body\" style:default-outline-level=\"{n}\">\
             <style:text-properties fo:font-size=\"{size}pt\" fo:font-weight=\"bold\"/>\
             </style:style>"
        ));
    }

    format!(
        r##"<?xml version="1.0" encoding="UTF-8"?>
<office:document-styles xmlns:office="urn:oasis:names:tc:opendocument:xmlns:office:1.0" xmlns:style="urn:oasis:names:tc:opendocument:xmlns:style:1.0" xmlns:text="urn:oasis:names:tc:opendocument:xmlns:text:1.0" xmlns:fo="urn:oasis:names:tc:opendocument:xmlns:xsl-fo-compatible:1.0" xmlns:svg="urn:oasis:names:tc:opendocument:xmlns:svg-compatible:1.0" office:version="1.2">
 <office:styles>
  <style:default-style style:family="paragraph">
   <style:paragraph-properties fo:hyphenation-ladder-count="no-limit"/>
   <style:text-properties fo:font-size="11pt" fo:language="en" fo:country="US"/>
  </style:default-style>
  <style:style style:name="Standard" style:family="paragraph" style:class="text"/>
  <style:style style:name="Text_20_body" style:display-name="Text body" style:family="paragraph" style:parent-style-name="Standard" style:class="text">
   <style:paragraph-properties fo:margin-top="0in" fo:margin-bottom="0.1in"/>
  </style:style>
  <style:style style:name="Heading" style:family="paragraph" style:parent-style-name="Standard" style:next-style-name="Text_20_body" style:class="text">
   <style:paragraph-properties fo:margin-top="0.2in" fo:margin-bottom="0.08in" fo:keep-with-next="always"/>
   <style:text-properties fo:font-size="14pt" fo:font-weight="bold"/>
  </style:style>
  {headings}
  <style:style style:name="Chapter_20_Break" style:display-name="Chapter Break" style:family="paragraph" style:parent-style-name="Heading_20_1" style:next-style-name="Text_20_body" style:default-outline-level="1">
   <style:paragraph-properties fo:break-before="page"/>
  </style:style>
  <style:style style:name="Chapter_20_Caption" style:display-name="Chapter Caption" style:family="paragraph" style:parent-style-name="Standard" style:next-style-name="Text_20_body" style:class="text">
   <style:paragraph-properties fo:margin-top="0in" fo:margin-bottom="0.2in"/>
   <style:text-properties fo:font-style="italic" fo:font-size="12pt" fo:color="#666666"/>
  </style:style>
  <style:style style:name="Quotations" style:family="paragraph" style:parent-style-name="Standard" style:class="html">
   <style:paragraph-properties fo:margin-left="0.4in" fo:margin-right="0.4in" fo:margin-top="0.05in" fo:margin-bottom="0.05in"/>
   <style:text-properties fo:font-style="italic"/>
  </style:style>
  <style:style style:name="Preformatted_Text" style:display-name="Preformatted Text" style:family="paragraph" style:parent-style-name="Standard" style:class="html">
   <style:paragraph-properties fo:margin-top="0in" fo:margin-bottom="0in"/>
   <style:text-properties style:font-name="Liberation Mono" fo:font-family="'Liberation Mono'" style:font-family-generic="modit" fo:font-size="10pt"/>
  </style:style>
  <style:style style:name="Horizontal_Line" style:display-name="Horizontal Line" style:family="paragraph" style:parent-style-name="Standard" style:class="html">
   <style:paragraph-properties fo:margin-top="0.05in" fo:margin-bottom="0.1in" fo:border-bottom="0.5pt solid #808080" fo:padding="0in" style:join-border="false"/>
  </style:style>
  <style:style style:name="T_bold" style:family="text">
   <style:text-properties fo:font-weight="bold"/>
  </style:style>
  <style:style style:name="T_italic" style:family="text">
   <style:text-properties fo:font-style="italic"/>
  </style:style>
  <style:style style:name="T_bolditalic" style:family="text">
   <style:text-properties fo:font-weight="bold" fo:font-style="italic"/>
  </style:style>
  <style:style style:name="T_strike" style:family="text">
   <style:text-properties style:text-line-through-style="solid" style:text-line-through-type="single"/>
  </style:style>
  <style:style style:name="Source_20_Text" style:display-name="Source Text" style:family="text">
   <style:text-properties style:font-name="Liberation Mono" fo:font-family="'Liberation Mono'" style:font-family-generic="modit" fo:font-size="10pt"/>
  </style:style>
  <style:style style:name="Internet_20_Link" style:display-name="Internet Link" style:family="text">
   <style:text-properties fo:color="#0563c1" style:text-underline-style="solid" style:text-underline-width="auto" style:text-underline-color="font-color"/>
  </style:style>
  <text:list-style style:name="L_bullet">
   <text:list-level-style-bullet text:level="1" text:bullet-char="&#8226;"><style:list-level-properties text:space-before="0.25in" text:min-label-width="0.25in"/></text:list-level-style-bullet>
   <text:list-level-style-bullet text:level="2" text:bullet-char="&#9702;"><style:list-level-properties text:space-before="0.5in" text:min-label-width="0.25in"/></text:list-level-style-bullet>
   <text:list-level-style-bullet text:level="3" text:bullet-char="&#9642;"><style:list-level-properties text:space-before="0.75in" text:min-label-width="0.25in"/></text:list-level-style-bullet>
  </text:list-style>
  <text:list-style style:name="L_number">
   <text:list-level-style-number text:level="1" style:num-format="1" text:num-suffix="."><style:list-level-properties text:space-before="0.25in" text:min-label-width="0.25in"/></text:list-level-style-number>
   <text:list-level-style-number text:level="2" style:num-format="a" text:num-suffix="."><style:list-level-properties text:space-before="0.5in" text:min-label-width="0.25in"/></text:list-level-style-number>
   <text:list-level-style-number text:level="3" style:num-format="i" text:num-suffix="."><style:list-level-properties text:space-before="0.75in" text:min-label-width="0.25in"/></text:list-level-style-number>
  </text:list-style>
 </office:styles>
 <office:automatic-styles>
  <style:page-layout style:name="pm1">
   <style:page-layout-properties fo:page-width="8.5in" fo:page-height="11in" fo:margin-top="1in" fo:margin-bottom="1in" fo:margin-left="1in" fo:margin-right="1in"/>
  </style:page-layout>
 </office:automatic-styles>
 <office:master-styles>
  <style:master-page style:name="Standard" style:page-layout-name="pm1"/>
 </office:master-styles>
</office:document-styles>"##
    )
}

fn content_xml(chapters: &[Chapter]) -> String {
    let mut body = String::new();
    for (i, chapter) in chapters.iter().enumerate() {
        // Chapter heading (always level 1); the document's own headings are
        // shifted down by one so they nest beneath it. Every chapter after the
        // first starts on a new page via a heading style with a page break.
        let heading_style = if i == 0 {
            "Heading_20_1"
        } else {
            "Chapter_20_Break"
        };
        body.push_str(&format!(
            "<text:h text:style-name=\"{heading_style}\" text:outline-level=\"1\">{}</text:h>",
            esc(&chapter.title)
        ));
        if let Some(slug) = chapter.slug.as_deref().map(str::trim).filter(|s| !s.is_empty()) {
            // Italic at both the paragraph-style and character-run level so the
            // caption stays italic regardless of how a reader applies styles.
            body.push_str(&format!(
                "<text:p text:style-name=\"Chapter_20_Caption\">\
                 <text:span text:style-name=\"T_italic\">{}</text:span></text:p>",
                esc(slug)
            ));
        }
        body.push_str(&markdown_to_body(&chapter.markdown, 1));
    }

    format!(
        r#"<?xml version="1.0" encoding="UTF-8"?>
<office:document-content xmlns:office="urn:oasis:names:tc:opendocument:xmlns:office:1.0" xmlns:style="urn:oasis:names:tc:opendocument:xmlns:style:1.0" xmlns:text="urn:oasis:names:tc:opendocument:xmlns:text:1.0" xmlns:fo="urn:oasis:names:tc:opendocument:xmlns:xsl-fo-compatible:1.0" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:svg="urn:oasis:names:tc:opendocument:xmlns:svg-compatible:1.0" office:version="1.2">
 <office:body>
  <office:text>
   {body}
  </office:text>
 </office:body>
</office:document-content>"#
    )
}

/// Write the chapters to an .odt file at `out_path`.
pub fn export(chapters: &[Chapter], out_path: &Path) -> std::io::Result<()> {
    let file = std::fs::File::create(out_path)?;
    let mut zip = zip::ZipWriter::new(file);

    // mimetype MUST be the first entry and stored without compression.
    let stored = SimpleFileOptions::default().compression_method(zip::CompressionMethod::Stored);
    zip.start_file("mimetype", stored)
        .map_err(to_io)?;
    zip.write_all(MIMETYPE.as_bytes())?;

    let deflated =
        SimpleFileOptions::default().compression_method(zip::CompressionMethod::Deflated);

    zip.add_directory("META-INF/", deflated).map_err(to_io)?;
    zip.start_file("META-INF/manifest.xml", deflated)
        .map_err(to_io)?;
    zip.write_all(manifest_xml().as_bytes())?;

    zip.start_file("styles.xml", deflated).map_err(to_io)?;
    zip.write_all(styles_xml().as_bytes())?;

    zip.start_file("content.xml", deflated).map_err(to_io)?;
    zip.write_all(content_xml(chapters).as_bytes())?;

    zip.finish().map_err(to_io)?;
    Ok(())
}

fn to_io(e: zip::result::ZipError) -> std::io::Error {
    std::io::Error::new(std::io::ErrorKind::Other, e)
}

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

    #[test]
    fn body_covers_common_markdown() {
        let md = "\
Some **bold** and *italic* and ***both*** and `code` and ~~gone~~.

## A subheading

- one
- two
  - nested

1. first
2. second

> a quote

```
let x = 1;
    indented();
```

A [link](https://example.com) and a rule:

---

Done.";
        let body = markdown_to_body(md, 1);
        assert!(body.contains("<text:span text:style-name=\"T_bold\">bold</text:span>"));
        assert!(body.contains("<text:span text:style-name=\"T_italic\">italic</text:span>"));
        assert!(body.contains("T_bolditalic"));
        assert!(body.contains("Source_20_Text"));
        assert!(body.contains("T_strike"));
        // Heading level 2 in source shifts to Heading_20_3 (offset 1).
        assert!(body.contains("text:style-name=\"Heading_20_3\""));
        assert!(body.contains("<text:list text:style-name=\"L_bullet\">"));
        assert!(body.contains("<text:list text:style-name=\"L_number\">"));
        assert!(body.contains("Quotations"));
        assert!(body.contains("Preformatted_Text"));
        assert!(body.contains("xlink:href=\"https://example.com\""));
        assert!(body.contains("Horizontal_Line"));
        // spaces in indented code preserved
        assert!(body.contains("<text:s text:c=\"4\"/>"));
    }

    #[test]
    fn export_writes_valid_archive() {
        let chapters = vec![
            Chapter {
                title: "Chapter One".to_string(),
                slug: Some("the opening".to_string()),
                markdown: "Hello **world**.\n\n## Scene\n\nText.".to_string(),
            },
            Chapter {
                title: "Chapter Two".to_string(),
                slug: None,
                markdown: "- a\n- b\n".to_string(),
            },
        ];
        let dir = std::env::temp_dir();
        let out = dir.join("md_manuscript_test.odt");
        export(&chapters, &out).expect("export ok");

        // Re-open the archive and check required members exist with mimetype first.
        let file = std::fs::File::open(&out).unwrap();
        let mut zip = zip::ZipArchive::new(file).unwrap();
        assert_eq!(zip.file_names().next().unwrap(), "mimetype");
        let names: Vec<String> = zip.file_names().map(|s| s.to_string()).collect();
        for required in ["mimetype", "META-INF/manifest.xml", "styles.xml", "content.xml"] {
            assert!(names.iter().any(|n| n == required), "missing {required}");
        }
        use std::io::Read;
        let mut content = String::new();
        zip.by_name("content.xml")
            .unwrap()
            .read_to_string(&mut content)
            .unwrap();
        assert!(content.contains(">Chapter One</text:h>"));
        assert!(content.contains(">Chapter Two</text:h>"));
        // The first chapter uses the plain heading; later chapters get a page break.
        assert!(content.contains(
            "<text:h text:style-name=\"Heading_20_1\" text:outline-level=\"1\">Chapter One</text:h>"
        ));
        assert!(content.contains(
            "<text:h text:style-name=\"Chapter_20_Break\" text:outline-level=\"1\">Chapter Two</text:h>"
        ));
        // The slug renders as an italic caption paragraph under the first chapter.
        assert!(content.contains(
            "<text:p text:style-name=\"Chapter_20_Caption\">\
             <text:span text:style-name=\"T_italic\">the opening</text:span></text:p>"
        ));

        // The page-break style is defined in styles.xml.
        let mut styles = String::new();
        zip.by_name("styles.xml")
            .unwrap()
            .read_to_string(&mut styles)
            .unwrap();
        assert!(styles.contains("style:name=\"Chapter_20_Break\""));
        assert!(styles.contains("fo:break-before=\"page\""));
    }
}