use super::sexp::Token;
use crate::compare::util::get_offsets;
use crate::parser::Document;
use crate::parser::DocumentElement;
use crate::parser::Heading;
use crate::parser::Section;

#[derive(Debug)]
pub struct DiffResult {
    status: DiffStatus,
    name: String,
    children: Vec<DiffResult>,
}

#[derive(Debug, PartialEq)]
pub enum DiffStatus {
    Good,
    Bad,
}

impl DiffResult {
    pub fn print(&self) -> Result<(), Box<dyn std::error::Error>> {
        self.print_indented(0)
    }

    fn print_indented(&self, indentation: usize) -> Result<(), Box<dyn std::error::Error>> {
        let status_text = {
            match self.status {
                DiffStatus::Good => {
                    if self.has_bad_children() {
                        "BADCHILD"
                    } else {
                        "GOOD"
                    }
                }
                DiffStatus::Bad => "BAD",
            }
        };
        println!("{}{} {}", "  ".repeat(indentation), status_text, self.name);
        for child in self.children.iter() {
            child.print_indented(indentation + 1)?;
        }
        Ok(())
    }

    pub fn has_bad_children(&self) -> bool {
        self.children
            .iter()
            .any(|child| child.status == DiffStatus::Bad || child.has_bad_children())
    }
}

pub fn compare_document<'s>(
    emacs: &'s Token<'s>,
    rust: &'s Document<'s>,
) -> Result<DiffResult, Box<dyn std::error::Error>> {
    let children = emacs.as_list()?;
    let first_child = children.first().ok_or("Should have at least one child.")?;
    let first_child_text = first_child.as_atom()?;
    if first_child_text != "org-data" {
        return Err("Document should correspond to an org-data cell.".into());
    }
    let mut child_status = Vec::new();
    let mut this_status = DiffStatus::Good;

    // Skipping "org-data" and the first parameter which is often nil
    for (i, token) in children.iter().skip(2).enumerate() {
        let section_or_headline = token.as_list()?;
        let first_cell = section_or_headline
            .first()
            .ok_or("Should have at least one child.")?
            .as_atom()?;
        if first_cell == "section" {
            if i != 0 {
                return Err("Section cannot be after the first child of document.".into());
            }
            child_status.push(compare_section(
                rust.source,
                token,
                rust.zeroth_section
                    .as_ref()
                    .ok_or("No corresponding zeroth-section")?,
            )?);
        } else if first_cell == "headline" {
            let corresponding_heading = rust
                .children
                .iter()
                .nth(i - rust.zeroth_section.as_ref().map(|_| 1).unwrap_or(0))
                .ok_or("Should have a corresponding heading.")?;
            child_status.push(compare_heading(rust.source, token, corresponding_heading)?);
        } else {
            return Err("Document should only contain sections and headlines.".into());
        }
    }

    Ok(DiffResult {
        status: this_status,
        name: "document".to_owned(),
        children: child_status,
    })
}

pub fn compare_section<'s>(
    source: &'s str,
    emacs: &'s Token<'s>,
    rust: &'s Section<'s>,
) -> Result<DiffResult, Box<dyn std::error::Error>> {
    let children = emacs.as_list()?;
    let first_child = children.first().ok_or("Should have at least one child.")?;
    let first_child_text = first_child.as_atom()?;
    if first_child_text != "section" {
        return Err("Section should correspond to a section cell.".into());
    }
    let mut child_status = Vec::new();
    let mut this_status = DiffStatus::Good;

    let attributes_child = children
        .iter()
        .nth(1)
        .ok_or("Should have an attributes child.")?;
    let attributes_map = attributes_child.as_map()?;
    let begin = attributes_map
        .get(":begin")
        .ok_or("Missing :begin attribute.")?
        .as_atom()?;
    let end = attributes_map
        .get(":end")
        .ok_or("Missing :end attribute.")?
        .as_atom()?;
    let (rust_begin, rust_end) = get_offsets(source, rust);
    if (rust_begin + 1).to_string() != begin || (rust_end + 1).to_string() != end {
        this_status = DiffStatus::Bad;
    }

    Ok(DiffResult {
        status: this_status,
        name: "section".to_owned(),
        children: child_status,
    })
}

pub fn compare_heading<'s>(
    source: &'s str,
    emacs: &'s Token<'s>,
    rust: &'s Heading<'s>,
) -> Result<DiffResult, Box<dyn std::error::Error>> {
    let children = emacs.as_list()?;
    let first_child = children.first().ok_or("Should have at least one child.")?;
    let first_child_text = first_child.as_atom()?;
    if first_child_text != "headline" {
        return Err("Heading should correspond to a headline cell.".into());
    }
    let mut child_status = Vec::new();
    let mut this_status = DiffStatus::Good;

    let attributes_child = children
        .iter()
        .nth(1)
        .ok_or("Should have an attributes child.")?;
    let attributes_map = attributes_child.as_map()?;
    let begin = attributes_map
        .get(":begin")
        .ok_or("Missing :begin attribute.")?
        .as_atom()?;
    let end = attributes_map
        .get(":end")
        .ok_or("Missing :end attribute.")?
        .as_atom()?;
    let (rust_begin, rust_end) = get_offsets(source, rust);
    if (rust_begin + 1).to_string() != begin || (rust_end + 1).to_string() != end {
        this_status = DiffStatus::Bad;
    }

    for (emacs_child, rust_child) in children.iter().skip(2).zip(rust.children.iter()) {
        match rust_child {
            DocumentElement::Heading(rust_heading) => {
                child_status.push(compare_heading(source, emacs_child, rust_heading)?);
            },
            DocumentElement::Section(rust_section) => {
                child_status.push(compare_section(source, emacs_child, rust_section)?);
            },
        };
    }

    Ok(DiffResult {
        status: this_status,
        name: "heading".to_owned(),
        children: child_status,
    })
}