use std::collections::HashMap;
use std::path::{Path, PathBuf};
use std::result::Result as StdResult;

use tera::{Tera, Context as TeraContext};
use serde::ser::{SerializeStruct, self};

use config::Config;
use front_matter::{SectionFrontMatter, split_section_content};
use errors::{Result, ResultExt};
use utils::fs::read_file;
use utils::templates::render_template;
use utils::site::get_reading_analytics;
use rendering::{RenderContext, Header, render_content};

use page::Page;
use file_info::FileInfo;


#[derive(Clone, Debug, PartialEq)]
pub struct Section {
    /// All info about the actual file
    pub file: FileInfo,
    /// The front matter meta-data
    pub meta: SectionFrontMatter,
    /// The URL path of the page
    pub path: String,
    /// The components for the path of that page
    pub components: Vec<String>,
    /// The full URL for that page
    pub permalink: String,
    /// The actual content of the page, in markdown
    pub raw_content: String,
    /// The HTML rendered of the page
    pub content: String,
    /// All direct pages of that section
    pub pages: Vec<Page>,
    /// All pages that cannot be sorted in this section
    pub ignored_pages: Vec<Page>,
    /// All direct subsections
    pub subsections: Vec<Section>,
    /// Toc made from the headers of the markdown file
    pub toc: Vec<Header>,
}

impl Section {
    pub fn new<P: AsRef<Path>>(file_path: P, meta: SectionFrontMatter) -> Section {
        let file_path = file_path.as_ref();

        Section {
            file: FileInfo::new_section(file_path),
            meta,
            path: "".to_string(),
            components: vec![],
            permalink: "".to_string(),
            raw_content: "".to_string(),
            content: "".to_string(),
            pages: vec![],
            ignored_pages: vec![],
            subsections: vec![],
            toc: vec![],
        }
    }

    pub fn parse(file_path: &Path, content: &str, config: &Config) -> Result<Section> {
        let (meta, content) = split_section_content(file_path, content)?;
        let mut section = Section::new(file_path, meta);
        section.raw_content = content.clone();
        section.path = format!("{}/", section.file.components.join("/"));
        section.components = section.path.split('/')
            .map(|p| p.to_string())
            .filter(|p| !p.is_empty())
            .collect::<Vec<_>>();
        section.permalink = config.make_permalink(&section.path);
        Ok(section)
    }

    /// Read and parse a .md file into a Page struct
    pub fn from_file<P: AsRef<Path>>(path: P, config: &Config) -> Result<Section> {
        let path = path.as_ref();
        let content = read_file(path)?;

        Section::parse(path, &content, config)
    }

    pub fn get_template_name(&self) -> String {
        match self.meta.template {
            Some(ref l) => l.to_string(),
            None => {
                if self.is_index() {
                    return "index.html".to_string();
                }
                "section.html".to_string()
            },
        }
    }

    /// We need access to all pages url to render links relative to content
    /// so that can't happen at the same time as parsing
    pub fn render_markdown(&mut self, permalinks: &HashMap<String, String>, tera: &Tera, config: &Config) -> Result<()> {
        let mut context = RenderContext::new(
            tera,
            config,
            &self.permalink,
            permalinks,
            self.meta.insert_anchor_links,
        );

        context.tera_context.add("section", self);

        let res = render_content(&self.raw_content, &context)
            .chain_err(|| format!("Failed to render content of {}", self.file.path.display()))?;
        self.content = res.0;
        self.toc = res.1;
        Ok(())
    }

    /// Renders the page using the default layout, unless specified in front-matter
    pub fn render_html(&self, tera: &Tera, config: &Config) -> Result<String> {
        let tpl_name = self.get_template_name();

        let mut context = TeraContext::new();
        context.add("config", config);
        context.add("section", self);
        context.add("current_url", &self.permalink);
        context.add("current_path", &self.path);

        render_template(&tpl_name, tera, &context, &config.theme)
            .chain_err(|| format!("Failed to render section '{}'", self.file.path.display()))
    }

    /// Is this the index section?
    pub fn is_index(&self) -> bool {
        self.file.components.is_empty()
    }

    /// Returns all the paths of the pages belonging to that section
    pub fn all_pages_path(&self) -> Vec<PathBuf> {
        let mut paths = vec![];
        paths.extend(self.pages.iter().map(|p| p.file.path.clone()));
        paths.extend(self.ignored_pages.iter().map(|p| p.file.path.clone()));
        paths
    }

    /// Whether the page given belongs to that section
    pub fn is_child_page(&self, path: &PathBuf) -> bool {
        self.all_pages_path().contains(path)
    }
}

impl ser::Serialize for Section {
    fn serialize<S>(&self, serializer: S) -> StdResult<S::Ok, S::Error> where S: ser::Serializer {
        let mut state = serializer.serialize_struct("section", 13)?;
        state.serialize_field("content", &self.content)?;
        state.serialize_field("permalink", &self.permalink)?;
        state.serialize_field("title", &self.meta.title)?;
        state.serialize_field("description", &self.meta.description)?;
        state.serialize_field("extra", &self.meta.extra)?;
        state.serialize_field("path", &self.path)?;
        state.serialize_field("components", &self.components)?;
        state.serialize_field("permalink", &self.permalink)?;
        state.serialize_field("pages", &self.pages)?;
        state.serialize_field("subsections", &self.subsections)?;
        let (word_count, reading_time) = get_reading_analytics(&self.raw_content);
        state.serialize_field("word_count", &word_count)?;
        state.serialize_field("reading_time", &reading_time)?;
        state.serialize_field("toc", &self.toc)?;
        state.end()
    }
}

/// Used to create a default index section if there is no _index.md in the root content directory
impl Default for Section {
    fn default() -> Section {
        Section {
            file: FileInfo::default(),
            meta: SectionFrontMatter::default(),
            path: "".to_string(),
            components: vec![],
            permalink: "".to_string(),
            raw_content: "".to_string(),
            content: "".to_string(),
            pages: vec![],
            ignored_pages: vec![],
            subsections: vec![],
            toc: vec![],
        }
    }
}