const std = @import("std");
const util = @import("util.zig");
const cw = @import("width.zig");

/// Returns the terminal cell width of `string`, ignoring ANSI escape
/// sequences. Wide code points (CJK, fullwidth, emoji) count as 2 cells and
/// combining marks as 0; see [width.zig] for coverage caveats.
pub fn cellWidth(string: []const u8) u16 {
    var width: u16 = 0;
    var i: usize = 0;
    while (i < string.len) {
        const b = string[i];
        if (b == 0x1b) {
            i = skipEscape(string, i);
            continue;
        }
        const len = std.unicode.utf8ByteSequenceLength(b) catch {
            // Invalid lead byte: count one cell, advance one byte.
            width = util.satAdd(width, 1);
            i += 1;
            continue;
        };
        if (i + len > string.len) {
            width = util.satAdd(width, 1);
            i += 1;
            continue;
        }
        const cp = std.unicode.utf8Decode(string[i .. i + len]) catch {
            width = util.satAdd(width, 1);
            i += 1;
            continue;
        };
        width = util.satAdd(width, cw.codepointWidth(cp));
        i += len;
    }
    return width;
}

pub fn maxLineWidth(string: []const u8) u16 {
    var max: u16 = 0;
    var start: usize = 0;
    var i: usize = 0;
    while (i < string.len) : (i += 1) {
        if (string[i] == '\n') {
            const w = cellWidth(string[start..i]);
            if (w > max) max = w;
            start = i + 1;
        }
    }
    if (start < string.len) {
        const w = cellWidth(string[start..]);
        if (w > max) max = w;
    }
    return max;
}

/// Returns the number of lines in `string`, mirroring lipgloss `Height`:
/// `count('\n') + 1`. Empty input is one line; a trailing `\n` adds a line.
pub fn lineCount(string: []const u8) u16 {
    const nls = std.mem.count(u8, string, "\n");
    return @intCast(@min(nls + 1, util.max_dim));
}

fn skipEscape(string: []const u8, index: usize) usize {
    if (index + 1 >= string.len) return string.len;
    switch (string[index + 1]) {
        '[' => {
            var j = index + 2;
            while (j < string.len and (string[j] < 0x40 or string[j] > 0x7e)) : (j += 1) {}
            return if (j < string.len) j + 1 else string.len;
        },
        ']' => {
            var j = index + 2;
            while (j < string.len) : (j += 1) {
                if (string[j] == 0x07) return j + 1;
                if (string[j] == 0x1b and j + 1 < string.len and string[j + 1] == '\\') return j + 2;
            }
            return string.len;
        },
        else => return index + 2,
    }
}

test "cellWidth plain ASCII" {
    try std.testing.expectEqual(@as(u16, 5), cellWidth("hello"));
}

test "cellWidth strips CSI" {
    try std.testing.expectEqual(@as(u16, 5), cellWidth("\x1b[31mhello\x1b[0m"));
}

test "cellWidth control chars are zero" {
    try std.testing.expectEqual(@as(u16, 0), cellWidth("\x07"));
}

test "cellWidth wide CJK" {
    try std.testing.expectEqual(@as(u16, 4), cellWidth("世界"));
}

test "cellWidth emoji" {
    try std.testing.expectEqual(@as(u16, 2), cellWidth("🎉"));
}

test "cellWidth combining mark is zero width" {
    // "e" + U+0301 combining acute accent renders in a single cell.
    try std.testing.expectEqual(@as(u16, 1), cellWidth("e\u{0301}"));
}

test "cellWidth mixed ascii and wide" {
    try std.testing.expectEqual(@as(u16, 7), cellWidth("ab世界c"));
}

test "maxLineWidth multi-line" {
    try std.testing.expectEqual(@as(u16, 5), maxLineWidth("hi\nworld\na"));
}

test "lineCount" {
    try std.testing.expectEqual(@as(u16, 1), lineCount(""));
    try std.testing.expectEqual(@as(u16, 1), lineCount("hi"));
    try std.testing.expectEqual(@as(u16, 2), lineCount("hi\nthere"));
    try std.testing.expectEqual(@as(u16, 3), lineCount("hi\nthere\n"));
    try std.testing.expectEqual(@as(u16, 3), lineCount("a\n\nb"));
}