use crate::parser::parse_scenario_snippet;
use crate::Bindings;
use crate::MatchedScenario;
use crate::PartialStep;
use crate::Scenario;
use crate::ScenarioStep;
use crate::StepKind;
use crate::{Error, Result};

use pandoc_ast::{Attr, Block, Inline, Map, MetaValue, MutVisitor, Pandoc};
use serde::{Deserialize, Serialize};

use roadmap;

use std::io::prelude::*;
use std::path::Path;
use std::process::{Command, Stdio};

/// A parsed Subplot document.
///
/// Pandoc works by parsing its various input files and constructing
/// an abstract syntax tree or AST. When Pandoc generates output, it
/// works based on the AST. This way, the input parsing and output
/// generation are cleanly separated.
///
/// A Pandoc filter can modify the AST before output generation
/// starts working. This allows the filter to make changes to what
/// gets output, without having to understand the input documents at
/// all.
///
/// This function is a Pandoc filter, to be use with
/// pandoc_ast::filter, for typesetting Subplot documents.
///
/// # Example
///
/// fix this example;
/// ~~~~
/// let markdown = "\
/// ---
/// title: Test Title
/// ...
/// This is a test document.
/// ";
///
/// use std::io::Write;
/// use tempfile::NamedTempFile;
/// let mut f = NamedTempFile::new().unwrap();
/// f.write_all(markdown.as_bytes()).unwrap();
/// let filename = f.path();
///
/// use subplot;
/// let doc = subplot::Document::from_file(filename).unwrap();
/// assert_eq!(doc.files(), &[]);
/// ~~~~
#[derive(Debug)]
pub struct Document {
    ast: Pandoc,
    meta: Metadata,
    files: DataFiles,
}

impl<'a> Document {
    fn new(ast: Pandoc, meta: Metadata, files: DataFiles) -> Document {
        Document { ast, meta, files }
    }

    /// Construct a Document from a JSON AST
    pub fn from_json(json: &str) -> Result<Document> {
        let mut ast: Pandoc = serde_json::from_str(json)?;
        let meta = Metadata::new(&ast)?;
        let files = DataFiles::new(&mut ast);
        Ok(Document::new(ast, meta, files))
    }

    /// Construct a Document from a named file.
    ///
    /// The file can be in any format Pandoc understands. This runs
    /// Pandoc to parse the file into an AST, so it can be a little
    /// slow.
    pub fn from_file(filename: &Path) -> Result<Document> {
        let mut pandoc = pandoc::new();
        pandoc.add_input(&filename);
        pandoc.set_output_format(pandoc::OutputFormat::Json, vec![]);
        pandoc.set_output(pandoc::OutputKind::Pipe);
        let output = match pandoc.execute()? {
            pandoc::PandocOutput::ToFile(_) => return Err(Error::NotJson),
            pandoc::PandocOutput::ToBuffer(o) => o,
        };
        let doc = Document::from_json(&output)?;
        Ok(doc)
    }

    /// Return the AST of a Document, serialized as JSON.
    ///
    /// This is useful in a Pandoc filter, so that the filter can give
    /// it back to Pandoc for typesetting.
    pub fn ast(&self) -> Result<String> {
        let json = serde_json::to_string(&self.ast)?;
        Ok(json)
    }

    /// Return the document's metadata.
    pub fn meta(&self) -> &Metadata {
        &self.meta
    }

    /// Return list of files embeddedin the document.
    pub fn files(&self) -> &[DataFile] {
        self.files.files()
    }

    /// Check that document has a title in its metadata.
    pub fn has_title(&self) -> Result<()> {
        if self.meta().title().is_empty() {
            Err(Error::no_title())
        } else {
            Ok(())
        }
    }

    /// Typeset a Subplot document.
    pub fn typeset(&mut self) {
        let mut visitor = TypesettingVisitor::new(&self.meta.bindings);
        visitor.walk_pandoc(&mut self.ast);
    }

    /// Return all scenarios in a document.
    pub fn scenarios(&mut self) -> Result<Vec<Scenario>> {
        let mut visitor = StructureVisitor::new();
        visitor.walk_pandoc(&mut self.ast);

        let mut scenarios: Vec<Scenario> = vec![];

        let mut i = 0;
        while i < visitor.elements.len() {
            let (maybe, new_i) = extract_scenario(&visitor.elements[i..])?;
            if let Some(scen) = maybe {
                scenarios.push(scen);
            }
            i += new_i;
        }
        Ok(scenarios)
    }

    /// Return matched scenarios in a document.
    pub fn matched_scenarios(&mut self) -> Result<Vec<MatchedScenario>> {
        let scenarios = self.scenarios()?;
        let bindings = self.meta().bindings();
        let vec: Result<Vec<MatchedScenario>> = scenarios
            .iter()
            .map(|scen| MatchedScenario::new(scen, bindings))
            .collect();
        Ok(vec?)
    }
}

fn extract_scenario(e: &[Element]) -> Result<(Option<Scenario>, usize)> {
    if e.is_empty() {
        // If we get here, it's a programming error.
        panic!("didn't expect empty list of elements");
    }

    match &e[0] {
        Element::Snippet(_) => Err(Error::scenario_before_heading()),
        Element::Heading(title, level) => {
            let mut scen = Scenario::new(&title);
            for (i, item) in e.iter().enumerate().skip(1) {
                match item {
                    Element::Heading(_, level2) => {
                        let is_subsection = *level2 > *level;
                        if is_subsection {
                            if scen.has_steps() {
                            } else {
                                return Ok((None, i));
                            }
                        } else if scen.has_steps() {
                            return Ok((Some(scen), i));
                        } else {
                            return Ok((None, i));
                        }
                    }
                    Element::Snippet(text) => {
                        for line in parse_scenario_snippet(&text) {
                            let step = ScenarioStep::new_from_str(line)?;
                            scen.add(&step);
                        }
                    }
                }
            }
            if scen.has_steps() {
                Ok((Some(scen), e.len()))
            } else {
                Ok((None, e.len()))
            }
        }
    }
}

#[cfg(test)]
mod test_extract {
    use super::extract_scenario;
    use super::Element;
    use crate::Error;
    use crate::Result;
    use crate::Scenario;

    fn h(title: &str, level: i64) -> Element {
        Element::Heading(title.to_string(), level)
    }

    fn s(text: &str) -> Element {
        Element::Snippet(text.to_string())
    }

    fn check_result(r: Result<(Option<Scenario>, usize)>, title: Option<&str>, i: usize) {
        eprintln!("checking result: {:?}", r);
        assert!(r.is_ok());
        let (actual_scen, actual_i) = r.unwrap();
        if title.is_none() {
            assert!(actual_scen.is_none());
        } else {
            assert!(actual_scen.is_some());
            let scen = actual_scen.unwrap();
            assert_eq!(scen.title(), title.unwrap());
        }
        assert_eq!(actual_i, i);
    }

    #[test]
    fn returns_nothing_if_there_is_no_scenario() {
        let elements: Vec<Element> = vec![h("title", 1)];
        let r = extract_scenario(&elements);
        check_result(r, None, 1);
    }

    #[test]
    fn returns_scenario_if_there_is_one() {
        let elements = vec![h("title", 1), s("given something")];
        let r = extract_scenario(&elements);
        check_result(r, Some("title"), 2);
    }

    #[test]
    fn skips_scenarioless_section_in_favour_of_same_level() {
        let elements = vec![h("first", 1), h("second", 1), s("given something")];
        let r = extract_scenario(&elements);
        check_result(r, None, 1);
        let r = extract_scenario(&elements[1..]);
        check_result(r, Some("second"), 2);
    }

    #[test]
    fn returns_parent_section_with_scenario_snippet() {
        let elements = vec![
            h("1", 1),
            s("given something"),
            h("1.1", 2),
            s("when something"),
            h("2", 1),
        ];
        let r = extract_scenario(&elements);
        check_result(r, Some("1"), 4);
        let r = extract_scenario(&elements[4..]);
        check_result(r, None, 1);
    }

    #[test]
    fn skips_scenarioless_parent_heading() {
        let elements = vec![h("1", 1), h("1.1", 2), s("given something"), h("2", 1)];

        let r = extract_scenario(&elements);
        check_result(r, None, 1);

        let r = extract_scenario(&elements[1..]);
        check_result(r, Some("1.1"), 2);

        let r = extract_scenario(&elements[3..]);
        check_result(r, None, 1);
    }

    #[test]
    fn skips_scenarioless_deeper_headings() {
        let elements = vec![h("1", 1), h("1.1", 2), h("2", 1), s("given something")];

        let r = extract_scenario(&elements);
        check_result(r, None, 1);

        let r = extract_scenario(&elements[1..]);
        check_result(r, None, 1);

        let r = extract_scenario(&elements[2..]);
        check_result(r, Some("2"), 2);
    }

    #[test]
    fn returns_error_if_scenario_has_no_title() {
        let elements = vec![s("given something")];
        let r = extract_scenario(&elements);
        match r {
            Err(Error::ScenarioBeforeHeading) => (),
            _ => panic!("unexpected result {:?}", r),
        }
    }
}

/// Metadata of a document, as needed by Subplot.
#[derive(Debug)]
pub struct Metadata {
    title: String,
    bindings_filename: Option<String>,
    bindings: Bindings,
    functions_filename: Option<String>,
}

impl Metadata {
    /// Construct a Metadata from a Document, if possible.
    pub fn new(doc: &Pandoc) -> Result<Metadata> {
        let title = get_title(&doc.meta)?;
        let bindings_filename = get_bindings_filename(&doc.meta)?;
        let functions_filename = get_functions_filename(&doc.meta)?;
        let mut bindings = Bindings::new();
        if let Some(ref filename) = bindings_filename {
            get_bindings(filename, &mut bindings)?;
        }
        Ok(Metadata {
            title,
            bindings_filename,
            bindings,
            functions_filename,
        })
    }

    /// Return title of document.
    pub fn title(&self) -> &str {
        &self.title
    }

    /// Return filename where bindings are specified.
    pub fn bindings_filename(&self) -> Option<&str> {
        match &self.bindings_filename {
            Some(filename) => Some(&filename),
            None => None,
        }
    }

    /// Return filename where functions are specified.
    pub fn functions_filename(&self) -> Option<&str> {
        match &self.functions_filename {
            Some(filename) => Some(&filename),
            None => None,
        }
    }

    /// Return the bindings.
    pub fn bindings(&self) -> &Bindings {
        &self.bindings
    }
}

type Mapp = Map<String, MetaValue>;

fn get_title(map: &Mapp) -> Result<String> {
    if let Some(s) = get_string(map, "title") {
        Ok(s)
    } else {
        Ok("".to_string())
    }
}

fn get_bindings_filename(map: &Mapp) -> Result<Option<String>> {
    match get_string(map, "bindings") {
        Some(s) => Ok(Some(s)),
        None => Ok(None),
    }
}

fn get_functions_filename(map: &Mapp) -> Result<Option<String>> {
    match get_string(map, "functions") {
        Some(s) => Ok(Some(s)),
        None => Ok(None),
    }
}

fn get_string(map: &Mapp, field: &str) -> Option<String> {
    let v = match map.get(field) {
        None => return None,
        Some(s) => s,
    };
    let v = match v {
        pandoc_ast::MetaValue::MetaString(s) => s.to_string(),
        pandoc_ast::MetaValue::MetaInlines(vec) => join(&vec),
        _ => panic!("don't know how to handle: {:?}", v),
    };
    Some(v)
}

fn join(vec: &[Inline]) -> String {
    let mut buf = String::new();
    join_into_buffer(vec, &mut buf);
    buf
}

fn join_into_buffer(vec: &[Inline], buf: &mut String) {
    for item in vec {
        match item {
            pandoc_ast::Inline::Str(s) => buf.push_str(&s),
            pandoc_ast::Inline::Emph(v) => join_into_buffer(v, buf),
            pandoc_ast::Inline::Strong(v) => join_into_buffer(v, buf),
            pandoc_ast::Inline::Strikeout(v) => join_into_buffer(v, buf),
            pandoc_ast::Inline::Superscript(v) => join_into_buffer(v, buf),
            pandoc_ast::Inline::Subscript(v) => join_into_buffer(v, buf),
            pandoc_ast::Inline::SmallCaps(v) => join_into_buffer(v, buf),
            pandoc_ast::Inline::Space => buf.push_str(" "),
            pandoc_ast::Inline::SoftBreak => buf.push_str(" "),
            pandoc_ast::Inline::LineBreak => buf.push_str(" "),
            _ => panic!("unknown pandoc_ast::Inline component {:?}", item),
        }
    }
}

#[cfg(test)]
mod test_join {
    use super::join;
    use pandoc_ast::Inline;

    #[test]
    fn join_all_kinds() {
        let v = vec![
            Inline::Str("a".to_string()),
            Inline::Emph(vec![Inline::Str("b".to_string())]),
            Inline::Strong(vec![Inline::Str("c".to_string())]),
            Inline::Strikeout(vec![Inline::Str("d".to_string())]),
            Inline::Superscript(vec![Inline::Str("e".to_string())]),
            Inline::Subscript(vec![Inline::Str("f".to_string())]),
            Inline::SmallCaps(vec![Inline::Str("g".to_string())]),
            Inline::Space,
            Inline::SoftBreak,
            Inline::LineBreak,
        ];
        assert_eq!(join(&v), "abcdefg   ");
    }
}

fn get_bindings(filename: &str, bindings: &mut Bindings) -> Result<()> {
    bindings.add_from_file(&filename)?;
    Ok(())
}

// We need to have something to hang an impl of MutVisitor off of. The
// struct here will do, but doesn't otherwise matter and contains no
// data.
struct TypesettingVisitor<'a> {
    bindings: &'a Bindings,
}

impl<'a> TypesettingVisitor<'a> {
    fn new(bindings: &'a Bindings) -> Self {
        TypesettingVisitor { bindings }
    }
}

// Visit interesting parts of the Pandoc abstract syntax tree. The
// document top level is a vector of blocks and we visit that and
// replace any fenced code block with the scenario tag with a typeset
// paragraph. Also, replace fenced code blocks with dot or roadmap
// markup with the rendered SVG image.
impl<'a> MutVisitor for TypesettingVisitor<'a> {
    fn visit_vec_block(&mut self, vec_block: &mut Vec<Block>) {
        for block in vec_block {
            match block {
                Block::CodeBlock(attr, s) => {
                    if is_class(attr, "scenario") {
                        *block = scenario_snippet(&self.bindings, s)
                    } else if is_class(attr, "file") {
                        *block = file_block(attr, s)
                    } else if is_class(attr, "dot") {
                        *block = dot(s)
                    } else if is_class(attr, "roadmap") {
                        *block = roadmap_block(s)
                    }
                }
                _ => {
                    self.visit_block(block);
                }
            }
        }
    }
}

// Is a code block marked as being of a given type?
fn is_class(attr: &Attr, class: &str) -> bool {
    match attr {
        (_id, classes, _kvpairs) => classes.iter().any(|s| s == class),
    }
}

/// Typeset an error from dot as a Pandoc AST Block element.
pub fn error(err: Error) -> Block {
    let msg = format!("ERROR: {}", err.to_string());
    Block::Para(error_msg(&msg))
}

// Typeset an error message a vector of inlines.
pub fn error_msg(msg: &str) -> Vec<Inline> {
    vec![Inline::Strong(vec![inlinestr(msg)])]
}

/// Typeset a code block tagged as a file.
pub fn file_block(attr: &Attr, text: &str) -> Block {
    let filename = inlinestr(&attr.0);
    let filename = Inline::Strong(vec![filename]);
    let intro = Block::Plain(vec![inlinestr("File:"), space(), filename]);
    let codeblock = Block::CodeBlock(attr.clone(), text.to_string());
    let noattr = ("".to_string(), vec![], vec![]);
    Block::Div(noattr, vec![intro, codeblock])
}

/// Typeset a scenario snippet as a Pandoc AST Block.
///
/// Typesetting here means producing the Pandoc abstract syntax tree
/// nodes that result in the desired output, when Pandoc processes
/// them.
///
/// The snippet is given as a text string, which is parsed. It need
/// not be a complete scenario, but it should consist of complete steps.
pub fn scenario_snippet(bindings: &Bindings, snippet: &str) -> Block {
    let steps = parse_scenario_snippet(snippet)
        .map(|s| step(bindings, s))
        .collect();
    Block::LineBlock(steps)
}

// Typeset a single scenario step as a sequence of Pandoc AST Inlines.
fn step(bindings: &Bindings, text: &str) -> Vec<Inline> {
    let step = ScenarioStep::new_from_str(text);
    if step.is_err() {
        eprintln!("Could not parse step: {}", text);
        return error_msg(&format!("Could not parse step: {}", text));
    }
    let step = step.unwrap();

    let m = bindings.find(&step);
    if m.is_none() {
        eprintln!("Could not findind binding for: {}", text);
        return error_msg(&format!("Could not find binding for: {}", text));
    }
    let m = m.unwrap();

    let mut inlines = Vec::new();

    inlines.push(keyword(&step));
    inlines.push(space());

    for part in m.parts() {
        #[allow(unused_variables)]
        match part {
            PartialStep::UncapturedText(s) => inlines.push(uncaptured(s.text())),
            PartialStep::CapturedText { name, text } => inlines.push(captured(text)),
        }
    }

    inlines
}

// Typeset first word, which is assumed to be a keyword, of a scenario
// step.
fn keyword(step: &ScenarioStep) -> Inline {
    let word = match step.kind() {
        StepKind::Given => "given",
        StepKind::When => "when",
        StepKind::Then => "then",
    };
    let word = inlinestr(word);
    Inline::Emph(vec![word])
}

fn inlinestr(s: &str) -> Inline {
    Inline::Str(String::from(s))
}

// Typeset a space between words.
fn space() -> Inline {
    Inline::Space
}

// Typeset an uncaptured part of a step.
fn uncaptured(s: &str) -> Inline {
    inlinestr(s)
}

// Typeset a captured part of a step.
fn captured(s: &str) -> Inline {
    Inline::Strong(vec![inlinestr(s)])
}

/// Typeset a dot graph as SVG.
pub fn dot(dot: &str) -> Block {
    dot_to_block(dot)
}

/// Typeset a project roadmap expressed as textual YAML, and render it
/// as an SVG image.
pub fn roadmap_block(yaml: &str) -> Block {
    match roadmap::from_yaml(yaml) {
        Ok(ref mut roadmap) => {
            roadmap.set_missing_statuses();
            let width = 50;
            match roadmap.format_as_dot(width) {
                Ok(dot) => dot_to_block(&dot),
                Err(e) => Block::Para(vec![inlinestr(&e.to_string())]),
            }
        }
        Err(e) => Block::Para(vec![inlinestr(&e.to_string())]),
    }
}

// Take a dot graph, render it as SVG, and return an AST Block
// element. The Block will contain the SVG data. This allows the graph
// to be rendered without referending external entities.
fn dot_to_block(dot: &str) -> Block {
    match dot_to_svg(dot) {
        Ok(svg) => typeset_svg(svg),
        Err(err) => {
            eprintln!("dot failed: {}", err);
            error(err)
        }
    }
}

// Typeset an SVG, represented as a byte vector, as a Pandoc AST Block
// element.
fn typeset_svg(svg: Vec<u8>) -> Block {
    let url = svg_as_data_url(svg);
    let attr = ("".to_string(), vec![], vec![]);
    let img = Inline::Image(attr, vec![], (url, "".to_string()));
    Block::Para(vec![img])
}

// Convert an SVG, represented as a byte vector, into a data: URL,
// which can be inlined so the image can be rendered without
// referencing external files.
fn svg_as_data_url(svg: Vec<u8>) -> String {
    let svg = base64::encode(&svg);
    format!("data:image/svg+xml;base64,{}", svg)
}

// Generate an SVG from a textual graph description using the
// GraphViz dot language.
//
// This runs the dot command as a subprocess. That can always fail:
// dot might not be installed, or the input data might be malformed,
// or something else. Thus we capture and return any error from
// running dot.
//
// ~~~~
// let dot = r#"digraph "foo" { a -> b }"#;
// let svg = subplot::dot_to_svg(&dot).unwrap();
// assert!(svg.len() > 0);
// ~~~~
fn dot_to_svg(dot: &str) -> Result<Vec<u8>> {
    let mut child = Command::new("dot")
        .arg("-Tsvg")
        .stdin(Stdio::piped())
        .stdout(Stdio::piped())
        .stderr(Stdio::piped())
        .spawn()?;
    if let Some(stdin) = child.stdin.as_mut() {
        stdin.write_all(dot.as_bytes())?;
        let output = child.wait_with_output()?;
        if output.status.success() {
            Ok(output.stdout)
        } else {
            Err(Error::child_failed("dot", &output))
        }
    } else {
        Err(Error::child_no_stdin())
    }
}

// A structure element in the document: a heading or a scenario snippet.
#[derive(Debug)]
enum Element {
    // Headings consist of the text and the level of the heading.
    Heading(String, i64),

    // Scenario snippets consist just of the unparsed text.
    Snippet(String),
}

impl Element {
    pub fn heading(text: &str, level: i64) -> Element {
        Element::Heading(text.to_string(), level)
    }

    pub fn snippet(text: &str) -> Element {
        Element::Snippet(text.to_string())
    }
}

// A MutVisitor for extracting document structure.
struct StructureVisitor {
    elements: Vec<Element>,
}

impl StructureVisitor {
    pub fn new() -> Self {
        Self { elements: vec![] }
    }
}

impl MutVisitor for StructureVisitor {
    fn visit_vec_block(&mut self, vec_block: &mut Vec<Block>) {
        for block in vec_block {
            match block {
                Block::Header(level, _attr, inlines) => {
                    let text = join(inlines);
                    let heading = Element::heading(&text, *level);
                    self.elements.push(heading);
                }
                Block::CodeBlock(attr, s) => {
                    if is_class(attr, "scenario") {
                        let snippet = Element::snippet(s);
                        self.elements.push(snippet);
                    }
                }
                _ => {
                    self.visit_block(block);
                }
            }
        }
    }
}

/// A data file embedded in the document.
#[derive(Debug, Eq, PartialEq, Clone, Serialize, Deserialize)]
pub struct DataFile {
    filename: String,
    contents: String,
}

impl DataFile {
    fn new(filename: &str, contents: &str) -> DataFile {
        DataFile {
            filename: filename.to_string(),
            contents: contents.to_string(),
        }
    }

    pub fn filename(&self) -> &str {
        &self.filename
    }

    pub fn contents(&self) -> &str {
        &self.contents
    }
}

/// A collection of data files embedded in document.
#[derive(Debug, Eq, PartialEq, Clone, Serialize, Deserialize)]
struct DataFiles {
    files: Vec<DataFile>,
}

impl DataFiles {
    fn new(ast: &mut Pandoc) -> DataFiles {
        let mut files = DataFiles { files: vec![] };
        files.walk_pandoc(ast);
        files
    }

    fn files(&self) -> &[DataFile] {
        &self.files
    }
}

impl MutVisitor for DataFiles {
    fn visit_vec_block(&mut self, vec_block: &mut Vec<Block>) {
        for block in vec_block {
            match block {
                Block::CodeBlock(attr, contents) => {
                    if is_class(attr, "file") {
                        self.files
                            .push(DataFile::new(&get_filename(attr), &contents));
                    }
                }
                _ => {
                    self.visit_block(block);
                }
            }
        }
    }
}

fn get_filename(attr: &Attr) -> String {
    attr.0.to_string()
}