use crate::{Bindings, SubplotError, TemplateSpec, YamlMetadata};

use log::trace;
use std::collections::HashMap;
use std::fmt::Debug;
use std::ops::Deref;
use std::path::{Path, PathBuf};

/// Metadata of a document, as needed by Subplot.
#[derive(Debug)]
pub struct Metadata {
    basedir: PathBuf,
    title: String,
    date: Option<String>,
    markdown_filename: PathBuf,
    bindings_filenames: Vec<PathBuf>,
    bindings: Bindings,
    impls: HashMap<String, DocumentImpl>,
    bibliographies: Vec<PathBuf>,
    /// Extra class names which should be considered 'correct' for this document
    classes: Vec<String>,
}

#[derive(Debug)]
pub struct DocumentImpl {
    spec: TemplateSpec,
    functions: Vec<PathBuf>,
}

impl Metadata {
    /// Create from YamlMetadata.
    pub fn from_yaml_metadata<P>(
        basedir: P,
        yaml: &YamlMetadata,
        template: Option<&str>,
    ) -> Result<Self, SubplotError>
    where
        P: AsRef<Path> + Debug,
    {
        let mut bindings = Bindings::new();
        let bindings_filenames = if let Some(filenames) = yaml.bindings_filenames() {
            get_bindings(filenames, &mut bindings, template)?;
            filenames.iter().map(|p| p.to_path_buf()).collect()
        } else {
            vec![]
        };

        let mut impls = HashMap::new();

        for (impl_name, functions_filenames) in yaml.impls().iter() {
            let template_spec = load_template_spec(impl_name)?;
            let filenames = pathbufs("", functions_filenames);
            let docimpl = DocumentImpl::new(template_spec, filenames);
            impls.insert(impl_name.to_string(), docimpl);
        }

        let bibliographies = if let Some(v) = yaml.bibliographies() {
            v.iter().map(|s| s.to_path_buf()).collect()
        } else {
            vec![]
        };

        let classes = if let Some(v) = yaml.classes() {
            v.iter().map(|s| s.to_string()).collect()
        } else {
            vec![]
        };

        let meta = Self {
            basedir: basedir.as_ref().to_path_buf(),
            title: yaml.title().into(),
            date: yaml.date().map(|s| s.into()),
            markdown_filename: yaml.markdown().into(),
            bindings_filenames,
            bindings,
            impls,
            bibliographies,
            classes,
        };
        trace!("metadata: {:#?}", meta);

        Ok(meta)
    }

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

    /// Return date of document, if any.
    pub fn date(&self) -> Option<&str> {
        self.date.as_deref()
    }

    /// Return base dir for all relative filenames.
    pub fn basedir(&self) -> &Path {
        &self.basedir
    }

    /// Return filename of the markdown file.
    pub fn markdown_filename(&self) -> &Path {
        &self.markdown_filename
    }

    /// Return filename where bindings are specified.
    pub fn bindings_filenames(&self) -> Vec<&Path> {
        self.bindings_filenames.iter().map(|f| f.as_ref()).collect()
    }

    /// Return the document implementation (filenames, spec, etc) for the given template name
    pub fn document_impl(&self, template: &str) -> Option<&DocumentImpl> {
        self.impls.get(template)
    }

    /// Return the templates the document expects to implement
    pub fn templates(&self) -> impl Iterator<Item = &str> {
        self.impls.keys().map(String::as_str)
    }

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

    /// Return the bibliographies.
    pub fn bibliographies(&self) -> Vec<&Path> {
        self.bibliographies.iter().map(|x| x.as_path()).collect()
    }

    /// The classes which this document also claims are valid
    pub fn classes(&self) -> impl Iterator<Item = &str> {
        self.classes.iter().map(Deref::deref)
    }
}

impl DocumentImpl {
    fn new(spec: TemplateSpec, functions: Vec<PathBuf>) -> Self {
        Self { spec, functions }
    }

    pub fn functions_filenames(&self) -> impl Iterator<Item = &Path> {
        self.functions.iter().map(PathBuf::as_path)
    }

    pub fn spec(&self) -> &TemplateSpec {
        &self.spec
    }
}

fn load_template_spec(template: &str) -> Result<TemplateSpec, SubplotError> {
    let mut spec_path = PathBuf::from(template);
    spec_path.push("template");
    spec_path.push("template.yaml");
    TemplateSpec::from_file(&spec_path)
}

fn pathbufs<P>(basedir: P, v: &[PathBuf]) -> Vec<PathBuf>
where
    P: AsRef<Path>,
{
    let basedir = basedir.as_ref();
    v.iter().map(|p| basedir.join(p)).collect()
}

fn get_bindings<P>(
    filenames: &[P],
    bindings: &mut Bindings,
    template: Option<&str>,
) -> Result<(), SubplotError>
where
    P: AsRef<Path> + Debug,
{
    for filename in filenames {
        bindings.add_from_file(filename, template)?;
    }
    Ok(())
}