const Token = @import("Token.zig");
const std = @import("std");

pub fn stripWhiteSpace(line_with_white_space: []const u8) []const u8 {
    return std.mem.trimStart(u8, line_with_white_space, " \t");
}

pub fn countWhiteSpace(line_with_white_space: []const u8, tab_width: usize) usize {
    var sum: usize = 0;
    for (line_with_white_space) |char| {
        if (char == ' ') {
            sum += 1;
            continue;
        }
        if (char == '\t') {
            sum += tab_width;
            continue;
        }
        break;
    }
    return sum;
}

const DocumentStyle = struct {
    const Self = @This();

    heading_char: u8 = '#',
    heading_levels: usize = 6,
    unordered_chars: []const u8 = "-++*",

    pub const default = Self{
        .heading_char = '#',
        .heading_levels = 6,
        .unordered_chars = "-++*",
    };
};

pub const Document = struct {
    const Self = @This();

    const Newline = struct {
        chars: []const u8,

        pub const newline = Newline{
            .chars = "\n",
        };

        pub const newline_carriage_return = Newline{
            .chars = "\n\r",
        };
    };

    const FoundToken = bool;

    const StartLineParserFn = *const fn (self: *Self, alloc: std.mem.Allocator, line: *[]const u8) anyerror!FoundToken;
    const InlineParserFn = *const fn (self: *Self, alloc: std.mem.Allocator, line: *[]const u8) anyerror!FoundToken;
    const EndLineParserFn = *const fn (self: *Self, alloc: std.mem.Allocator, line: *[]const u8) anyerror!FoundToken;
    const MultiLineParserFn = *const fn (self: *Self, alloc: std.mem.Allocator, line_itter: *std.mem.SplitIterator(u8)) anyerror!void;

    tokens: std.ArrayList(Token) = .empty,
    tab_width: usize = 4,
    newline_char: Newline = .newline,

    document_style: DocumentStyle = .default,

    // each function will
    start_line_parsers: std.ArrayList(StartLineParserFn) = .empty,
    inline_parsers: std.ArrayList(InlineParserFn) = .empty,
    end_line_parsers: std.ArrayList(EndLineParserFn) = .empty,

    pub fn initDefault(alloc: std.mem.Allocator) !Self {
        var doc = Self{
            .tab_width = 4,
            .newline_char = .newline,
            .document_style = .default,
        };

        try doc.appendStartLineParsers(alloc, &[_]StartLineParserFn{
            &headingParser,
            &listOrderedParser,
        });

        try doc.appendInlineParsers(alloc, &[_]InlineParserFn{
            &baseLineParser,
        });

        return doc;
    }

    pub fn appendStartLineParsers(self: *Self, alloc: std.mem.Allocator, parser_fns: []const StartLineParserFn) !void {
        try self.start_line_parsers.appendSlice(alloc, parser_fns);
    }
    pub fn appendInlineParsers(self: *Self, alloc: std.mem.Allocator, parser_fns: []const InlineParserFn) !void {
        try self.inline_parsers.appendSlice(alloc, parser_fns);
    }
    pub fn appendEndLineParsers(self: *Self, alloc: std.mem.Allocator, parser_fns: []const EndLineParserFn) !void {
        try self.end_line_parsers.appendSlice(alloc, parser_fns);
    }

    pub fn deinit(self: *Self, alloc: std.mem.Allocator) void {
        self.tokens.deinit(alloc);
        self.start_line_parsers.deinit(alloc);
        self.end_line_parsers.deinit(alloc);
        self.inline_parsers.deinit(alloc);
    }

    fn consumeChars(line: *[]const u8, amount_of_chars_to_consume: usize) error{too_many_chars_to_consume}!void {
        if (line.len < amount_of_chars_to_consume) return error.too_many_chars_to_consume;
        line.* = line.*[amount_of_chars_to_consume..];
    }

    fn baseLineParser(self: *Self, alloc: std.mem.Allocator, line: *[]const u8) !FoundToken {
        try self.tokens.append(alloc, Token{
            .data = stripWhiteSpace(line.*),
            .padding = countWhiteSpace(line.*, self.tab_width),
            .type = .text,
        });
        return true;
    }

    // im going to need to hide a stack in here somewhere
    fn inlineParser(self: *Self, alloc: std.mem.Allocator, line: *[]const u8) !void {
        if (line.len == 0) return;

        for (self.inline_parsers.items) |parser| {
            _ = try parser(self, alloc, line);
        }
    }

    fn appendNewLineToken(self: *Self, alloc: std.mem.Allocator) !void {
        try self.tokens.append(alloc, Token{
            .data = "\n",
            .padding = 0,
            .type = .newline,
        });
    }

    pub fn parse(self: *Self, alloc: std.mem.Allocator, document: []const u8) !void {
        var line_iter = std.mem.splitSequence(u8, document, self.newline_char.chars);

        while (line_iter.next()) |line| {
            var current_line = line;

            for (self.start_line_parsers.items) |parser| {
                std.debug.print("line : \"{s}\"\n", .{line});
                const token_found = try parser(self, alloc, &current_line);

                if (token_found) break;
            }

            try self.inlineParser(alloc, &current_line);

            try self.appendNewLineToken(alloc);
        }
    }

    pub fn headingParser(self: *Self, alloc: std.mem.Allocator, line: *[]const u8) !FoundToken {
        // ignore empty lines
        if (line.len == 0) return false;

        const heading_end_index: usize = blk: {
            var i: usize = 0;
            while (i < self.document_style.heading_levels) : (i += 1) {
                if (line.*[i] == self.document_style.heading_char) continue;
                break;
            }
            break :blk i;
        };

        // if no heading was detected
        if (heading_end_index == 0) return false;

        // allows for blank headings
        const space_remove: usize = if (line.len == heading_end_index) 0 else 1;

        try self.tokens.append(alloc, Token{
            .data = line.*[0..heading_end_index],
            .padding = 0,
            .type = .heading,
        });

        try consumeChars(line, heading_end_index + space_remove);

        return true;
    }

    pub fn listOrderedParser(self: *Self, alloc: std.mem.Allocator, line: *[]const u8) !FoundToken {
        const clean_line = stripWhiteSpace(line.*);
        const whitespace_chars_removed = countWhiteSpace(line.*, self.tab_width);
        // check for the min length of chars
        if (clean_line.len < 2) return false;

        // find a point within the line
        const index_of_dot = blk: {
            if (std.mem.indexOf(u8, clean_line, ". ")) |i| {
                break :blk i;
            }
            return false;
        };
        const number = clean_line[0..index_of_dot];
        // if it has any spaces its not a order list id
        if (std.mem.containsAtLeastScalar(u8, number, 1, ' ') or
            std.mem.containsAtLeastScalar(u8, number, 1, '\t'))
        {
            return false;
        }
        // now work out what the number is
        // "I": 1,
        // "V": 5,
        // "X": 10,
        // "L": 50,
        // "C": 100,
        // "D": 500,
        // "M": 1000

        // roman numerials ill deal with these later

        // these can be the same
        // numbers

        // letters & roman (at least all the i's)

        const is_number = blk: {
            _ = std.fmt.parseInt(usize, number, 10) catch break :blk false;
            break :blk true;
        };
        const is_letter = std.ascii.isAlphabetic(number[0]);

        // might change this so lists can start from 0 like a real programmer
        if (is_number or is_letter) {
            try self.tokens.append(alloc, Token{
                .data = line.*[0 .. whitespace_chars_removed + number.len + 1],
                .padding = whitespace_chars_removed,
                .type = .ordered_list,
            });

            try consumeChars(line, whitespace_chars_removed + number.len + 2);
        }

        return false;
    }

    pub fn listUnorderedParser(self: *Self, alloc: std.mem.Allocator, line: *[]const u8) !FoundToken {
        const clean_line = stripWhiteSpace(line);
        const whitespace_chars_removed = @intFromPtr(clean_line.ptr) - @intFromPtr(line.ptr);
        // check for the min length of chars
        if (clean_line.len < 2) return null;

        // check there is a space seperating the char and the text
        if (clean_line[1] != ' ') return null;

        if (clean_line[0] == '-' or clean_line[0] == '=' or clean_line[0] == '+' or clean_line[0] == '*') {
            return LineParserReturn{
                // +2 to remove "-. "
                .pointer_offset = whitespace_chars_removed + 2,
                .token = .{
                    .data = clean_line[0..1],
                    .type = .unordered_list,
                },
            };
        }

        return null;
    }
};