// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use std::cmp;

use syntax::codemap::{self, CodeMap, BytePos};

use utils::{round_up_to_power_of_two, make_indent};
use comment::{FindUncommented, rewrite_comment, find_comment_end};

#[derive(Eq, PartialEq, Debug, Copy, Clone)]
pub enum ListTactic {
    // One item per row.
    Vertical,
    // All items on one row.
    Horizontal,
    // Try Horizontal layout, if that fails then vertical
    HorizontalVertical,
    // Pack as many items as possible per row over (possibly) many rows.
    Mixed,
}

#[derive(Eq, PartialEq, Debug, Copy, Clone)]
pub enum SeparatorTactic {
    Always,
    Never,
    Vertical,
}

impl_enum_decodable!(SeparatorTactic, Always, Never, Vertical);

// TODO having some helpful ctors for ListFormatting would be nice.
pub struct ListFormatting<'a> {
    pub tactic: ListTactic,
    pub separator: &'a str,
    pub trailing_separator: SeparatorTactic,
    pub indent: usize,
    // Available width if we layout horizontally.
    pub h_width: usize,
    // Available width if we layout vertically
    pub v_width: usize,
    // Non-expressions, e.g. items, will have a new line at the end of the list.
    // Important for comment styles.
    pub ends_with_newline: bool,
}

pub struct ListItem {
    pub pre_comment: Option<String>,
    // Item should include attributes and doc comments
    pub item: String,
    pub post_comment: Option<String>,
}

impl ListItem {
    pub fn is_multiline(&self) -> bool {
        self.item.contains('\n') || self.pre_comment.is_some() ||
        self.post_comment.as_ref().map(|s| s.contains('\n')).unwrap_or(false)
    }

    pub fn has_line_pre_comment(&self) -> bool {
        self.pre_comment.as_ref().map_or(false, |comment| comment.starts_with("//"))
    }

    pub fn from_str<S: Into<String>>(s: S) -> ListItem {
        ListItem { pre_comment: None, item: s.into(), post_comment: None }
    }
}

// Format a list of commented items into a string.
// FIXME: this has grown into a monstrosity
// TODO: add unit tests
pub fn write_list<'b>(items: &[ListItem], formatting: &ListFormatting<'b>) -> String {
    if items.len() == 0 {
        return String::new();
    }

    let mut tactic = formatting.tactic;

    // Conservatively overestimates because of the changing separator tactic.
    let sep_count = if formatting.trailing_separator != SeparatorTactic::Never {
        items.len()
    } else {
        items.len() - 1
    };
    let sep_len = formatting.separator.len();
    let total_sep_len = (sep_len + 1) * sep_count;
    let total_width = calculate_width(items);
    let fits_single = total_width + total_sep_len <= formatting.h_width;

    // Check if we need to fallback from horizontal listing, if possible.
    if tactic == ListTactic::HorizontalVertical {
        debug!("write_list: total_width: {}, total_sep_len: {}, h_width: {}",
               total_width, total_sep_len, formatting.h_width);
        tactic = if fits_single &&
                    !items.iter().any(ListItem::is_multiline) {
            ListTactic::Horizontal
        } else {
            ListTactic::Vertical
        };
    }

    // Check if we can fit everything on a single line in mixed mode.
    // The horizontal tactic does not break after v_width columns.
    if tactic == ListTactic::Mixed && fits_single {
        tactic = ListTactic::Horizontal;
    }

    // Switch to vertical mode if we find non-block comments.
    if items.iter().any(ListItem::has_line_pre_comment) {
        tactic = ListTactic::Vertical;
    }

    // Now that we know how we will layout, we can decide for sure if there
    // will be a trailing separator.
    let trailing_separator = needs_trailing_separator(formatting.trailing_separator, tactic);

    // Create a buffer for the result.
    // TODO could use a StringBuffer or rope for this
    let alloc_width = if tactic == ListTactic::Horizontal {
        total_width + total_sep_len
    } else {
        total_width + items.len() * (formatting.indent + 1)
    };
    let mut result = String::with_capacity(round_up_to_power_of_two(alloc_width));

    let mut line_len = 0;
    let indent_str = &make_indent(formatting.indent);
    for (i, item) in items.iter().enumerate() {
        let first = i == 0;
        let last = i == items.len() - 1;
        let separate = !last || trailing_separator;
        let item_sep_len = if separate { sep_len } else { 0 };
        let item_width = item.item.len() + item_sep_len;

        match tactic {
            ListTactic::Horizontal if !first => {
                result.push(' ');
            }
            ListTactic::Vertical if !first => {
                result.push('\n');
                result.push_str(indent_str);
            }
            ListTactic::Mixed => {
                let total_width = total_item_width(item) + item_sep_len;

                if line_len > 0 && line_len + total_width > formatting.v_width {
                    result.push('\n');
                    result.push_str(indent_str);
                    line_len = 0;
                }

                if line_len > 0 {
                    result.push(' ');
                    line_len += 1;
                }

                line_len += total_width;
            }
            _ => {}
        }

        // Pre-comments
        if let Some(ref comment) = item.pre_comment {
            result.push_str(&rewrite_comment(comment,
                                             // Block style in non-vertical mode
                                             tactic != ListTactic::Vertical,
                                             // Width restriction is only
                                             // relevant in vertical mode.
                                             formatting.v_width,
                                             formatting.indent));

            if tactic == ListTactic::Vertical {
                result.push('\n');
                result.push_str(indent_str);
            } else {
                result.push(' ');
            }
        }

        result.push_str(&item.item);

        // Post-comments
        if tactic != ListTactic::Vertical && item.post_comment.is_some() {
            let formatted_comment = rewrite_comment(item.post_comment.as_ref().unwrap(),
                                                    true,
                                                    formatting.v_width,
                                                    0);

            result.push(' ');
            result.push_str(&formatted_comment);
        }

        if separate {
            result.push_str(formatting.separator);
        }

        if tactic == ListTactic::Vertical && item.post_comment.is_some() {
            // 1 = space between item and comment.
            let width = formatting.v_width.checked_sub(item_width + 1).unwrap_or(1);
            let offset = formatting.indent + item_width + 1;
            let comment = item.post_comment.as_ref().unwrap();
            // Use block-style only for the last item or multiline comments.
            let block_style = formatting.ends_with_newline && last ||
                              comment.trim().contains('\n') ||
                              comment.trim().len() > width;

            let formatted_comment = rewrite_comment(comment, block_style, width, offset);

            result.push(' ');
            result.push_str(&formatted_comment);
        }
    }

    result
}

// Turns a list into a vector of items with associated comments.
// TODO: we probably do not want to take a terminator any more. Instead, we
// should demand a proper span end.
pub fn itemize_list<T, I, F1, F2, F3>(codemap: &CodeMap,
                                      prefix: Vec<ListItem>,
                                      it: I,
                                      separator: &str,
                                      terminator: &str,
                                      get_lo: F1,
                                      get_hi: F2,
                                      get_item_string: F3,
                                      mut prev_span_end: BytePos,
                                      next_span_start: BytePos)
                                      -> Vec<ListItem>
    where I: Iterator<Item = T>,
          F1: Fn(&T) -> BytePos,
          F2: Fn(&T) -> BytePos,
          F3: Fn(&T) -> String
{
    let mut result = prefix;
    result.reserve(it.size_hint().0);

    let mut new_it = it.peekable();
    let white_space: &[_] = &[' ', '\t'];

    while let Some(item) = new_it.next() {
        // Pre-comment
        let pre_snippet = codemap.span_to_snippet(codemap::mk_sp(prev_span_end,
                                                                get_lo(&item)))
                                 .unwrap();
        let pre_snippet = pre_snippet.trim();
        let pre_comment = if pre_snippet.len() > 0 {
            Some(pre_snippet.to_owned())
        } else {
            None
        };

        // Post-comment
        let next_start = match new_it.peek() {
            Some(ref next_item) => get_lo(next_item),
            None => next_span_start
        };
        let post_snippet = codemap.span_to_snippet(codemap::mk_sp(get_hi(&item),
                                                                  next_start))
                                  .unwrap();

        let comment_end = match new_it.peek() {
            Some(..) => {
                let block_open_index = post_snippet.find("/*");
                let newline_index = post_snippet.find('\n');
                let separator_index = post_snippet.find_uncommented(separator).unwrap();

                match (block_open_index, newline_index) {
                    // Separator before comment, with the next item on same line.
                    // Comment belongs to next item.
                    (Some(i), None) if i > separator_index => { separator_index + separator.len() }
                    // Block-style post-comment before the separator.
                    (Some(i), None) => {
                        cmp::max(find_comment_end(&post_snippet[i..]).unwrap() + i,
                                 separator_index + separator.len())
                    }
                    // Block-style post-comment. Either before or after the separator.
                    (Some(i), Some(j)) if i < j => {
                        cmp::max(find_comment_end(&post_snippet[i..]).unwrap() + i,
                                 separator_index + separator.len())
                    }
                    // Potential *single* line comment.
                    (_, Some(j)) => { j + 1 }
                    _ => post_snippet.len()
                }
            },
            None => {
                post_snippet.find_uncommented(terminator)
                            .unwrap_or(post_snippet.len())
            }
        };

        // Cleanup post-comment: strip separators and whitespace.
        prev_span_end = get_hi(&item) + BytePos(comment_end as u32);
        let mut post_snippet = post_snippet[..comment_end].trim();

        if post_snippet.starts_with(separator) {
            post_snippet = post_snippet[separator.len()..]
                .trim_matches(white_space);
        } else if post_snippet.ends_with(separator) {
            post_snippet = post_snippet[..post_snippet.len()-separator.len()]
                .trim_matches(white_space);
        }

        result.push(ListItem {
            pre_comment: pre_comment,
            item: get_item_string(&item),
            post_comment: if post_snippet.len() > 0 {
                Some(post_snippet.to_owned())
            } else {
                None
            }
        });
    }

    result
}

fn needs_trailing_separator(separator_tactic: SeparatorTactic, list_tactic: ListTactic) -> bool {
    match separator_tactic {
        SeparatorTactic::Always => true,
        SeparatorTactic::Vertical => list_tactic == ListTactic::Vertical,
        SeparatorTactic::Never => false,
    }
}

fn calculate_width(items: &[ListItem]) -> usize {
    items.iter().map(total_item_width).fold(0, |a, l| a + l)
}

fn total_item_width(item: &ListItem) -> usize {
    comment_len(&item.pre_comment) + comment_len(&item.post_comment) + item.item.len()
}

fn comment_len(comment: &Option<String>) -> usize {
    match comment {
        &Some(ref s) => {
            let text_len = s.trim().len();
            if text_len > 0 {
                // We'll put " /*" before and " */" after inline comments.
                text_len + 6
            } else {
                text_len
            }
        },
        &None => 0
    }
}