const std = @import("std");
const terminal = @import("../terminal.zig");

const isTaggedUnion = @import("../event.zig").isTaggedUnion;
const Error = @import("../event.zig").Error;
const Cell = terminal.Cell;

const log = std.log.scoped(.widget_text);

pub fn Widget(comptime Event: type, comptime Renderer: type) type {
    if (!isTaggedUnion(Event)) {
        @compileError("Provided user event `Event` for `Layout(comptime Event: type)` is not of type `union(enum)`.");
    }
    return struct {
        allocator: std.mem.Allocator,
        alignment: Alignment,
        contents: []const Cell,
        size: terminal.Size,
        require_render: bool,

        const Alignment = enum {
            default,
            center,
            top,
            bottom,
            left,
            right,
        };

        pub fn init(allocator: std.mem.Allocator, alignment: Alignment, contents: []const Cell) *@This() {
            var this = allocator.create(@This()) catch @panic("Text.zig: Failed to create");
            this.allocator = allocator;
            this.require_render = true;
            this.alignment = alignment;
            this.contents = contents;
            return this;
        }

        pub fn deinit(this: *@This()) void {
            this.allocator.destroy(this);
        }

        pub fn handle(this: *@This(), event: Event) ?Event {
            switch (event) {
                // store the received size
                .resize => |size| {
                    this.size = size;
                    this.require_render = true;
                },
                else => {},
            }
            return null;
        }

        pub fn render(this: *@This(), renderer: *Renderer) !void {
            if (!this.require_render) {
                return;
            }
            try renderer.clear(this.size);
            // update size for aligned contents, default will not change size
            const size: terminal.Size = blk: {
                switch (this.alignment) {
                    .default => break :blk this.size,
                    .center => {
                        var length_usize: usize = 0;
                        for (this.contents) |content| {
                            length_usize += content.content.len;
                        }
                        const length: u16 = @truncate(length_usize);
                        const cols = @min(length, this.size.cols);
                        const rows = cols / length;
                        break :blk .{
                            .anchor = .{
                                .col = this.size.anchor.col + @divTrunc(this.size.cols, 2) - @divTrunc(cols, 2),
                                .row = this.size.anchor.row + @divTrunc(this.size.rows, 2),
                            },
                            .rows = rows,
                            .cols = cols,
                        };
                    },
                    .top => {
                        var length_usize: usize = 0;
                        for (this.contents) |content| {
                            length_usize += content.content.len;
                        }
                        const length: u16 = @truncate(length_usize);
                        const cols = @min(length, this.size.cols);
                        const rows = cols / length;
                        break :blk .{
                            .anchor = .{
                                .col = this.size.anchor.col + @divTrunc(this.size.cols, 2) - @divTrunc(cols, 2),
                                .row = this.size.anchor.row,
                            },
                            .rows = rows,
                            .cols = cols,
                        };
                    },
                    .bottom => {
                        var length_usize: usize = 0;
                        for (this.contents) |content| {
                            length_usize += content.content.len;
                        }
                        const length: u16 = @truncate(length_usize);
                        const cols = @min(length, this.size.cols);
                        const rows = cols / length;
                        break :blk .{
                            .anchor = .{
                                .col = this.size.anchor.col + @divTrunc(this.size.cols, 2) - @divTrunc(cols, 2),
                                .row = this.size.anchor.row + this.size.rows - rows,
                            },
                            .rows = rows,
                            .cols = cols,
                        };
                    },
                    .left => {
                        var length_usize: usize = 0;
                        for (this.contents) |content| {
                            length_usize += content.content.len;
                        }
                        const length: u16 = @truncate(length_usize);
                        const cols = @min(length, this.size.cols);
                        const rows = cols / length;
                        break :blk .{
                            .anchor = .{
                                .col = this.size.anchor.col,
                                .row = this.size.anchor.row + @divTrunc(this.size.rows, 2) - @divTrunc(rows, 2),
                            },
                            .rows = rows,
                            .cols = cols,
                        };
                    },
                    .right => {
                        var length_usize: usize = 0;
                        for (this.contents) |content| {
                            length_usize += content.content.len;
                        }
                        const length: u16 = @truncate(length_usize);
                        const cols = @min(length, this.size.cols);
                        const rows = cols / length;
                        break :blk .{
                            .anchor = .{
                                .col = this.size.anchor.col + this.size.cols - cols,
                                .row = this.size.anchor.row + @divTrunc(this.size.rows, 2) - @divTrunc(rows, 2),
                            },
                            .rows = rows,
                            .cols = cols,
                        };
                    },
                }
            };
            try renderer.render(size, this.contents);
            this.require_render = false;
        }
    };
}