use crate::ast;
use crate::generate_test_program;
use crate::get_basedir_from;
use crate::visitor;
use crate::DataFile;
use crate::DataFiles;
use crate::LintingVisitor;
use crate::MatchedScenario;
use crate::Metadata;
use crate::PartialStep;
use crate::Scenario;
use crate::ScenarioStep;
use crate::Style;
use crate::{bindings::CaptureType, parser::parse_scenario_snippet};
use crate::{Result, SubplotError};
use crate::{Warning, Warnings};

use std::collections::HashSet;
use std::default::Default;
use std::fmt::Debug;
use std::ops::Deref;
use std::path::{Path, PathBuf};
use std::str::FromStr;

use pandoc_ast::{MutVisitor, Pandoc};

use log::{error, trace};

/// The set of known (special) classes which subplot will always recognise
/// as being valid.
static SPECIAL_CLASSES: &[&str] = &["scenario", "file", "dot", "pikchr", "plantuml", "roadmap"];

/// The set of known (file-type) classes which subplot will always recognise
/// as being valid.
static KNOWN_FILE_CLASSES: &[&str] = &["rust", "yaml", "python", "sh", "shell", "markdown", "bash"];

/// The set of known (special-to-pandoc) classes which subplot will always recognise
/// as being valid.  We include the subplot-specific noNumberLines class which we use
/// to invert the default numberLines on .file blocks.
static KNOWN_PANDOC_CLASSES: &[&str] = &["numberLines", "noNumberLines"];

/// 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 basedir = std::path::Path::new(".");
/// let style = subplot::Style::default();
/// let doc = subplot::Document::from_file(&basedir, filename, style, None).unwrap();
/// assert_eq!(doc.files(), &[]);
/// ~~~~
#[derive(Debug)]
pub struct Document {
    markdowns: Vec<PathBuf>,
    ast: Pandoc,
    meta: Metadata,
    files: DataFiles,
    style: Style,
    warnings: Warnings,
}

impl<'a> Document {
    fn new(
        markdowns: Vec<PathBuf>,
        ast: Pandoc,
        meta: Metadata,
        files: DataFiles,
        style: Style,
    ) -> Document {
        Document {
            markdowns,
            ast,
            meta,
            files,
            style,
            warnings: Warnings::default(),
        }
    }

    /// Return all warnings about this document.
    pub fn warnings(&self) -> &[Warning] {
        self.warnings.warnings()
    }

    fn from_ast<P>(
        basedir: P,
        markdowns: Vec<PathBuf>,
        mut ast: Pandoc,
        style: Style,
        template: Option<&str>,
    ) -> Result<Document>
    where
        P: AsRef<Path> + Debug,
    {
        let meta = Metadata::new(basedir, &ast, template)?;
        let mut linter = LintingVisitor::default();
        trace!("Walking AST for linting...");
        linter.walk_pandoc(&mut ast);
        if !linter.issues.is_empty() {
            // Currently we can't really return more than one error so return one
            return Err(linter.issues.remove(0));
        }
        let files = DataFiles::new(&mut ast);
        let doc = Document::new(markdowns, ast, meta, files, style);
        trace!("Loaded from JSON OK");
        Ok(doc)
    }

    /// Construct a Document from a JSON AST
    pub fn from_json<P>(
        basedir: P,
        markdowns: Vec<PathBuf>,
        json: &str,
        style: Style,
        template: Option<&str>,
    ) -> Result<Document>
    where
        P: AsRef<Path> + Debug,
    {
        trace!("Parsing document...");
        let ast: Pandoc = serde_json::from_str(json)?;
        Self::from_ast(basedir, markdowns, ast, style, template)
    }

    /// 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(
        basedir: &Path,
        filename: &Path,
        style: Style,
        template: Option<&str>,
    ) -> Result<Document> {
        trace!(
            "Document::from_file: basedir={} filename={}",
            basedir.display(),
            filename.display()
        );
        let markdowns = vec![filename.to_path_buf()];

        let mut pandoc = pandoc::new();
        pandoc.add_input(&filename);
        pandoc.set_input_format(
            pandoc::InputFormat::Markdown,
            vec![pandoc::MarkdownExtension::Citations],
        );
        pandoc.set_output_format(pandoc::OutputFormat::Json, vec![]);
        pandoc.set_output(pandoc::OutputKind::Pipe);

        // Add external Pandoc filters.
        crate::policy::add_citeproc(&mut pandoc);

        trace!("Invoking Pandoc to parse document {:?}", filename);
        let output = match pandoc.execute()? {
            pandoc::PandocOutput::ToBuffer(o) => o,
            _ => return Err(SubplotError::NotJson),
        };
        trace!("Pandoc was happy");
        let doc = Document::from_json(basedir, markdowns, &output, style, template)?;
        trace!("Loaded document OK");
        Ok(doc)
    }

    /// Construct a Document from a named file, using the pullmark_cmark crate.
    ///
    /// The file can be in the CommonMark format, with some
    /// extensions. This uses the pulldown-cmark crate to parse the
    /// file into an AST.
    pub fn from_file_with_pullmark(
        basedir: &Path,
        filename: &Path,
        style: Style,
        template: Option<&str>,
    ) -> Result<Document> {
        trace!("Parsing document with pullmark-cmark from {:?}", filename);
        let filename = filename.to_path_buf();
        let markdown = std::fs::read_to_string(&filename)?;
        let ast = ast::AbstractSyntaxTree::from_str(&markdown)?;

        trace!("Parsed document OK");
        Self::from_ast(basedir, vec![filename], ast.to_pandoc(), style, template)
    }

    /// 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 all source filenames for the document.
    ///
    /// The sources are any files that affect the output so that if
    /// the source file changes, the output needs to be re-generated.
    pub fn sources(&mut self, template: Option<&str>) -> Vec<PathBuf> {
        let mut names = vec![];

        for x in self.meta().bindings_filenames() {
            names.push(PathBuf::from(x))
        }

        if let Some(template) = template {
            if let Some(spec) = self.meta().document_impl(template) {
                for x in spec.functions_filenames() {
                    names.push(PathBuf::from(x));
                }
            }
        } else {
            for template in self.meta().templates() {
                if let Some(spec) = self.meta().document_impl(template) {
                    for x in spec.functions_filenames() {
                        names.push(PathBuf::from(x));
                    }
                }
            }
        }

        for x in self.meta().bibliographies().iter() {
            names.push(PathBuf::from(x))
        }

        for x in self.markdowns.iter() {
            names.push(x.to_path_buf());
        }

        let mut visitor = visitor::ImageVisitor::new();
        visitor.walk_pandoc(&mut self.ast);
        for x in visitor.images().iter() {
            names.push(x.to_path_buf());
        }

        names
    }

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

    /// Check the document for common problems.
    pub fn lint(&self) -> Result<()> {
        trace!("Linting document");
        self.check_doc_has_title()?;
        self.check_filenames_are_unique()?;
        self.check_block_classes()?;
        trace!("No linting problems found");
        Ok(())
    }

    // Check that all filenames for embedded files are unique.
    fn check_filenames_are_unique(&self) -> Result<()> {
        let mut known = HashSet::new();
        for filename in self.files().iter().map(|f| f.filename().to_lowercase()) {
            if known.contains(&filename) {
                return Err(SubplotError::DuplicateEmbeddedFilename(filename));
            }
            known.insert(filename);
        }
        Ok(())
    }

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

    /// Check that all the block classes in the document are known
    fn check_block_classes(&self) -> Result<()> {
        let mut visitor = visitor::BlockClassVisitor::default();
        // Irritatingly we can't immutably visit the AST for some reason
        // This clone() is expensive and unwanted, but I'm not sure how
        // to get around it for now
        visitor.walk_pandoc(&mut self.ast.clone());
        // Build the set of known good classes
        let mut known_classes: HashSet<String> = HashSet::new();
        for class in std::iter::empty()
            .chain(SPECIAL_CLASSES.iter().map(Deref::deref))
            .chain(KNOWN_FILE_CLASSES.iter().map(Deref::deref))
            .chain(KNOWN_PANDOC_CLASSES.iter().map(Deref::deref))
            .chain(self.meta().classes())
        {
            known_classes.insert(class.to_string());
        }
        // Acquire the set of used names which are not known
        let unknown_classes: Vec<_> = visitor
            .classes
            .difference(&known_classes)
            .cloned()
            .collect();
        // If the unknown classes list is not empty, we had a problem and
        // we will report it to the user.
        if !unknown_classes.is_empty() {
            Err(SubplotError::UnknownClasses(unknown_classes.join(", ")))
        } else {
            Ok(())
        }
    }

    /// Check that all named files (in matched steps) are actually present in the
    /// document.
    pub fn check_named_files_exist(&mut self, template: &str) -> Result<bool> {
        let filenames: HashSet<_> = self
            .files()
            .iter()
            .map(|f| f.filename().to_lowercase())
            .collect();
        trace!("Checking that files exist");
        let mut okay = true;
        let scenarios = match self.matched_scenarios(template) {
            Ok(scenarios) => scenarios,
            Err(_) => return Ok(true), // We can't do the check, so say it's okay.
        };
        for scenario in scenarios {
            for step in scenario.steps() {
                for captured in step.parts() {
                    if let PartialStep::CapturedText { name, text } = captured {
                        if matches!(step.types().get(name.as_str()), Some(CaptureType::File))
                            && !filenames.contains(&text.to_lowercase())
                        {
                            self.warnings.push(Warning::UnknownEmbeddedFile(
                                scenario.title().to_string(),
                                text.to_string(),
                            ));
                            okay = false;
                        }
                    }
                }
            }
        }
        Ok(okay)
    }

    /// Check that all embedded files are used by matched steps.
    pub fn check_embedded_files_are_used(&mut self, template: &str) -> Result<bool> {
        let mut filenames: HashSet<_> = self
            .files()
            .iter()
            .map(|f| f.filename().to_lowercase())
            .collect();
        trace!("Checking that files are used");
        let scenarios = match self.matched_scenarios(template) {
            Ok(scenarios) => scenarios,
            Err(_) => return Ok(true), // We can't do the check, so say it's okay.
        };
        for scenario in scenarios {
            for step in scenario.steps() {
                for captured in step.parts() {
                    if let PartialStep::CapturedText { name, text } = captured {
                        if matches!(step.types().get(name.as_str()), Some(CaptureType::File)) {
                            filenames.remove(&text.to_lowercase());
                        }
                    }
                }
            }
        }
        for filename in filenames.iter() {
            self.warnings
                .push(Warning::UnusedEmbeddedFile(filename.to_string()));
        }

        // We always succeed. Subplot's own subplot had valid cases of
        // an embedded file being used and we need to develop a way to
        // mark such uses as OK, before we can make it an error to not
        // use an embedded file in a scenario.
        Ok(true)
    }

    /// Check that all matched steps actually have function implementations
    pub fn check_matched_steps_have_impl(&mut self, template: &str) -> bool {
        trace!("Checking that steps have implementations");
        let mut okay = true;
        let scenarios = match self.matched_scenarios(template) {
            Ok(scenarios) => scenarios,
            Err(_) => return true, // No matches means no missing impls
        };
        trace!("Found {} scenarios", scenarios.len());
        for scenario in scenarios {
            trace!("Checking that steps in scenario");
            for step in scenario.steps() {
                if step.function().is_none() {
                    trace!("Missing step implementation: {:?}", step.text());
                    self.warnings.push(Warning::MissingStepImplementation(
                        scenario.title().to_string(),
                        step.text().to_string(),
                    ));
                    okay = false;
                }
            }
        }
        okay
    }

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

    /// Return all scenarios in a document.
    pub fn scenarios(&mut self) -> Result<Vec<Scenario>> {
        let mut visitor = 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, template: &str) -> Result<Vec<MatchedScenario>> {
        let scenarios = self.scenarios()?;
        trace!(
            "Found {} scenarios, checking their bindings",
            scenarios.len()
        );
        let bindings = self.meta().bindings();
        scenarios
            .iter()
            .map(|scen| MatchedScenario::new(template, scen, bindings))
            .collect()
    }

    /// Extract a template name from this document
    pub fn template(&self) -> Result<&str> {
        let templates: Vec<_> = self.meta().templates().collect();
        if templates.len() == 1 {
            Ok(templates[0])
        } else if templates.is_empty() {
            Err(SubplotError::MissingTemplate)
        } else {
            Err(SubplotError::AmbiguousTemplate)
        }
    }
}

/// Load a `Document` from a file.
///
/// This version uses Pandoc to parse the Markdown.
pub fn load_document<P>(filename: P, style: Style, template: Option<&str>) -> Result<Document>
where
    P: AsRef<Path> + Debug,
{
    let filename = filename.as_ref();
    let base_path = get_basedir_from(filename);
    trace!(
        "Loading document based at `{}` called `{}` with {:?}",
        base_path.display(),
        filename.display(),
        style
    );
    let doc = Document::from_file(&base_path, filename, style, template)?;
    trace!("Loaded doc from file OK");

    Ok(doc)
}

/// Load a `Document` from a file.
///
/// This version uses the `cmark-pullmark` crate to parse Markdown.
pub fn load_document_with_pullmark<P>(
    filename: P,
    style: Style,
    template: Option<&str>,
) -> Result<Document>
where
    P: AsRef<Path> + Debug,
{
    let filename = filename.as_ref();
    let base_path = get_basedir_from(filename);
    trace!(
        "Loading document based at `{}` called `{}` with {:?} using pullmark-cmark",
        base_path.display(),
        filename.display(),
        style
    );
    crate::resource::add_search_path(filename.parent().unwrap());
    let doc = Document::from_file_with_pullmark(&base_path, filename, style, template)?;
    trace!("Loaded doc from file OK");
    Ok(doc)
}

/// Generate code for one document.
pub fn codegen(filename: &Path, output: &Path, template: Option<&str>) -> Result<CodegenOutput> {
    let r = load_document_with_pullmark(filename, Style::default(), template);
    let mut doc = match r {
        Ok(doc) => doc,
        Err(err) => {
            return Err(err);
        }
    };
    doc.lint()?;
    let template = template
        .map(Ok)
        .unwrap_or_else(|| doc.template())?
        .to_string();
    trace!("Template: {:?}", template);
    if !doc.meta().templates().any(|t| t == template) {
        return Err(SubplotError::TemplateSupportNotPresent);
    }
    if !doc.check_named_files_exist(&template)?
        || !doc.check_matched_steps_have_impl(&template)
        || !doc.check_embedded_files_are_used(&template)?
    {
        error!("Found problems in document, cannot continue");
        std::process::exit(1);
    }

    trace!("Generating code");

    generate_test_program(&mut doc, output, &template)?;
    trace!("Finished generating code");

    Ok(CodegenOutput::new(template, doc))
}

pub struct CodegenOutput {
    pub template: String,
    pub doc: Document,
}

impl CodegenOutput {
    fn new(template: String, doc: Document) -> Self {
        Self { template, doc }
    }
}

fn extract_scenario(e: &[visitor::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] {
        visitor::Element::Snippet(_) => Err(SubplotError::ScenarioBeforeHeading),
        visitor::Element::Heading(title, level) => {
            let mut scen = Scenario::new(title);
            let mut prevkind = None;
            for (i, item) in e.iter().enumerate().skip(1) {
                match item {
                    visitor::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));
                        }
                    }
                    visitor::Element::Snippet(text) => {
                        for line in parse_scenario_snippet(text) {
                            let step = ScenarioStep::new_from_str(line, prevkind)?;
                            scen.add(&step);
                            prevkind = Some(step.kind());
                        }
                    }
                }
            }
            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::visitor::Element;
    use crate::Result;
    use crate::Scenario;
    use crate::SubplotError;

    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) {
        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(SubplotError::ScenarioBeforeHeading) => (),
            _ => panic!("unexpected result {:?}", r),
        }
    }
}