//// The object-centric document abstraction, as Gleam types.
////
//// A deliberate mirror of the D library's `ocda.model`, field for field.
//// The two are meant to agree, and the cheapest way to make that testable
//// is for them to hold the same things under the same names: the dump of a
//// loaded document is then identical by construction rather than by
//// negotiation.
////
//// Written against specs/sisudoc-abstraction-format: `ocda-model.md` for
//// the model, the two format specifications for what each serialisation
//// says about it.

import gleam/dict.{type Dict}
import gleam/list
import gleam/string

/// The format major version this library knows.
///
/// The `.ssp` and the `.ocda.db` carry one version between them, declared
/// in band. The minor part rises when a property is added and a reader of
/// the newer format still reads the older, so only the major is checked.
pub const format_major_read = "2"

/// The nine sections, in the order the format gives them, which is not the
/// order a sorted key list or a `group by` would give.
pub const section_names = [
  "head", "toc", "body", "endnotes", "glossary", "bibliography", "bookindex",
  "blurb", "tail",
]

/// The four blocks that are document preamble rather than sections of
/// objects.
pub const preamble_blocks = ["source", "meta", "make", "doc_has"]

/// A repeatable `.image` record: the file as the abstraction found it.
pub type Image {
  Image(
    /// filename as the object refers to it
    name: String,
    /// hex, uppercase
    sha256: String,
    bytes: Int,
    /// the file's own pixel dimensions, not any display width
    width: Int,
    height: Int,
    /// absent or unreadable, so no digest and no size
    missing: Bool,
    /// any further key:value fields, kept rather than dropped
    fields: Dict(String, String),
  )
}

pub fn new_image() -> Image {
  Image(
    name: "",
    sha256: "",
    bytes: 0,
    width: 0,
    height: 0,
    missing: False,
    fields: dict.new(),
  )
}

/// One object of the abstraction.
///
/// `text` is one string with the lines joined by newline, as in the D
/// library and for the same reason: an object whose only text line is
/// blank is then indistinguishable from an object with no text, in both
/// libraries, in the same place. A difference that exists in one language
/// and not the other would be worse than a loss both share.
pub type Object {
  Object(
    ocn: Int,
    /// one of the sixteen kinds
    is_a: String,
    /// the section this object was found in
    section: String,
    /// headings: A B C D 1 2 3 4
    heading_level: String,
    identifier: String,
    part: String,
    /// how the text behaves: para, block, comment
    is_of_type: String,
    /// the object's own section, when it differs from the block it sits in
    own_section: String,
    segment_html_is: String,
    segment_epub: String,
    segment_epub_is: String,
    table_aligns: String,
    stow_link: List(String),
    anchor_tags: List(String),
    parent_ocn: Int,
    last_descendant_ocn: Int,
    ocn_range_first: Int,
    ocn_range_last: Int,
    children: List(Int),
    ancestors: List(Int),
    dummy_heading: Bool,
    ocn_off: Bool,
    indent_base: Int,
    indent_hang: Int,
    bullet: Bool,
    lang: String,
    has_links: Bool,
    has_notes_reg: Bool,
    has_notes_star: Bool,
    has_images: Bool,
    segment: String,
    segment_prev: String,
    segment_next: String,
    anchor: String,
    heading_lev_anchor: String,
    table_cols: Int,
    table_widths: String,
    table_header: Bool,
    code_syntax: String,
    code_linenumbers: Bool,
    heading_ancestors_text: String,
    sha256: String,
    images: List(Image),
    text: String,
  )
}

pub fn new_object() -> Object {
  Object(
    ocn: 0,
    is_a: "",
    section: "",
    heading_level: "",
    identifier: "",
    part: "",
    is_of_type: "",
    own_section: "",
    segment_html_is: "",
    segment_epub: "",
    segment_epub_is: "",
    table_aligns: "",
    stow_link: [],
    anchor_tags: [],
    parent_ocn: 0,
    last_descendant_ocn: 0,
    ocn_range_first: 0,
    ocn_range_last: 0,
    children: [],
    ancestors: [],
    dummy_heading: False,
    ocn_off: False,
    indent_base: 0,
    indent_hang: 0,
    bullet: False,
    lang: "",
    has_links: False,
    has_notes_reg: False,
    has_notes_star: False,
    has_images: False,
    segment: "",
    segment_prev: "",
    segment_next: "",
    anchor: "",
    heading_lev_anchor: "",
    table_cols: 0,
    table_widths: "",
    table_header: False,
    code_syntax: "",
    code_linenumbers: False,
    heading_ancestors_text: "",
    sha256: "",
    images: [],
    text: "",
  )
}

/// Whether this object is rendered at all.
///
/// `is_of_type` "comment" is markup commentary: carried by the abstraction
/// so that nothing is lost, and not put into output. An output that
/// renders it leaks the author's notes into the document, which is what
/// spine itself does not do.
pub fn renders(object: Object) -> Bool {
  object.is_of_type != "comment"
}

/// The section this object belongs to: the block it sits in, unless it
/// says otherwise.
pub fn section_of(object: Object) -> String {
  case object.own_section {
    "" -> object.section
    own -> own
  }
}

/// What the loader met and did not understand.
///
/// A loader that silently drops what it does not know cannot say whether
/// it understood the document, and so cannot be used to check a
/// specification against an implementation: silence and understanding look
/// alike.
pub type Unknown {
  Unknown(
    /// `.name` -> times seen
    property: Dict(String, Int),
    /// `@name` -> times seen
    block: Dict(String, Int),
    /// first character -> times seen, for lines of no known shape
    line: Dict(String, Int),
  )
}

pub fn new_unknown() -> Unknown {
  Unknown(property: dict.new(), block: dict.new(), line: dict.new())
}

pub fn any_unknown(unknown: Unknown) -> Bool {
  dict.size(unknown.property) > 0
  || dict.size(unknown.block) > 0
  || dict.size(unknown.line) > 0
}

pub type Document {
  Document(
    /// as declared on line 1 of a `.ssp` or in `schema.version`, "" when
    /// absent
    format_version: String,
    source_filename: String,
    /// language, languages, digest
    source: Dict(String, String),
    unknown: Unknown,
    metadata: Dict(String, String),
    make: Dict(String, String),
    doc_has: Dict(String, String),
    /// section name -> objects, in document order
    sections: Dict(String, List(Object)),
  )
}

pub fn new_document() -> Document {
  Document(
    format_version: "",
    source_filename: "",
    source: dict.new(),
    unknown: new_unknown(),
    metadata: dict.new(),
    make: dict.new(),
    doc_has: dict.new(),
    sections: dict.new(),
  )
}

/// The major part of the declared version, "" when none was declared.
pub fn version_major(document: Document) -> String {
  case string.split_once(document.format_version, ".") {
    Ok(#(major, _)) -> major
    Error(_) -> document.format_version
  }
}

pub fn meta(document: Document, key: String) -> String {
  case dict.get(document.metadata, key) {
    Ok(value) -> value
    Error(_) -> ""
  }
}

/// The objects of a named section, empty when the document has none.
pub fn section(document: Document, name: String) -> List(Object) {
  case dict.get(document.sections, name) {
    Ok(objects) -> objects
    Error(_) -> []
  }
}

/// Is this one of the nine sections of the format?
pub fn is_section(name: String) -> Bool {
  list.contains(section_names, name)
}

/// Is this one of the four preamble blocks?
pub fn is_preamble_block(name: String) -> Bool {
  list.contains(preamble_blocks, name)
}