const std = @import("std");

const fs = @import("fs.zig");
const exe = @import("exe.zig");
const Context = @import("main.zig").Context;

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

pub fn generate(ctx: *Context) !void {
    ctx.progress_start("generate");
    defer ctx.progress_end();

    try genIndex(ctx);

    log.info("Generated index.", .{});

    try genSite(ctx);

    log.info("Generated {d} files.", .{ctx.generated});
    log.info("Generated {d} tildes.", .{ctx.tilde});
}

fn genIndex(ctx: *Context) !void {
    ctx.progress_start("index.htm");
    defer ctx.progress_end();

    const srcpathIndex = try fs.joinPathAndFilename(ctx.allocator(), &.{Context.params.PAGE_PATH}, &.{"index.htm"});
    defer ctx.allocator().free(srcpathIndex);

    const f = try fs.FileSwapper.createAt(ctx.allocator(), srcpathIndex);
    defer f.close();

    var buffer: [1024]u8 = undefined;
    var w = f.writer(&buffer);

    try w.interface.writeAll(
        \\<ul class="col2 captial">
        \\
    );

    // alphanum ascii sort
    std.mem.sort(
        []const u8,
        ctx.pages.items,
        {},
        struct {
            fn lessthan(_: void, a: []const u8, b: []const u8) bool {
                return std.ascii.lessThanIgnoreCase(a, b);
            }
        }.lessthan,
    );

    for (ctx.pages.items) |p| {
        if (std.mem.startsWith(u8, p, "meta.")) continue;

        const dstname = try fs.stripExtension(p);
        const dstpath = try fs.joinPathAndFilename(ctx.allocator(), &.{Context.params.SITE_PATH}, &.{ dstname, ".html" });
        defer ctx.allocator().free(dstpath);

        try w.interface.print(
            \\<li><a href="/{[LINK]s}">{[NAME]s}</a></li>
            \\
        , .{
            .LINK = dstpath,
            .NAME = dstname,
        });
    }

    try w.interface.writeAll(
        \\</ul>
        \\
    );

    try w.interface.flush();

    if (!try f.diff()) try f.undo();
}

fn genSite(ctx: *Context) !void {
    for (ctx.pages.items) |p| {
        const pname = std.fs.path.basename(p);

        ctx.progress_start(pname);
        defer ctx.progress_end();

        if (std.mem.startsWith(u8, pname, "meta.")) {
            try meta(ctx, p);
            continue;
        }

        const dstname = try fs.stripExtension(p);
        const srcpath = try fs.joinPathAndFilename(ctx.allocator(), &.{Context.params.PAGE_PATH}, &.{ dstname, ".htm" });
        defer ctx.allocator().free(srcpath);
        const dstpath = try fs.joinPathAndFilename(ctx.allocator(), &.{Context.params.SITE_PATH}, &.{ dstname, ".html" });
        defer ctx.allocator().free(dstpath);
        const rel_dstpath = try std.fs.path.relative(ctx.allocator(), Context.params.SITE_PATH, dstpath);
        defer ctx.allocator().free(rel_dstpath);

        log.debug("generating {s} at {s}", .{ p, rel_dstpath });

        if (std.fs.path.dirname(rel_dstpath)) |d| {
            const dstdir = try fs.joinPathAndFilename(ctx.allocator(), &.{Context.params.SITE_PATH}, &.{d});
            defer ctx.allocator().free(dstdir);

            try std.fs.cwd().makePath(dstdir);
        }

        const f = try fs.FileSwapper.createAt(ctx.allocator(), dstpath);
        defer f.close();

        var buffer: [1024]u8 = undefined;
        var w = f.writer(&buffer);

        const page_name = try std.mem.replaceOwned(u8, ctx.allocator(), dstname, "_", " ");
        defer ctx.allocator().free(page_name);

        try build(ctx.allocator(), &w.interface, page_name, srcpath);
        ctx.generated += 1;
    }
}

// build a single html file
fn build(allocator: std.mem.Allocator, w: *std.Io.Writer, page_name: []const u8, srcpath: []const u8) !void {
    const mtime = try fs.getLastEdit(srcpath);
    const mtime_str = try fs.formatTimespec(allocator, mtime, "%F");
    defer allocator.free(mtime_str);

    // HEAD
    try w.print(
        \\<!-- Generated file, do not edit, you may edit and discard {[SOURCE]s} :) -->
        \\<!DOCTYPE html>
        \\<html lang="en">
        \\<head>
        \\<meta charset="utf-8">
        \\<meta name="thumbnail" content="/media/services/thumbnail.jpg">
        \\<meta name="viewport" content="width=device-width,initial-scale=1">
        \\<link rel="preload" href="/media/interface/logo.svg" as="image">
        \\<link rel="alternate" type="application/rss+xml" title="RSS Feed" href="/links/rss.xml">
        \\<link rel="stylesheet" type="text/css" href="/links/main.css">
        \\<link rel="shortcut icon" type="image/png" href="/media/services/icon.png">
        \\<link rel="license" href="{[LICENSE_URL]s}">
        \\<title>{[SITE_NAME]s} &mdash; {[PAGE_NAME]s}</title>
        \\</head>
        \\<body>
        \\<header>
        \\<a href="/"><img src="/media/interface/logo.svg" alt="{[SITE_NAME]s}"></a>
        \\
    , .{
        .SOURCE = srcpath,
        .LICENSE_URL = Context.params.LICENSE_URL,
        .PAGE_NAME = page_name,
        .SITE_NAME = Context.params.SITE_NAME,
    });

    // NAV
    try w.writeAll(
        \\<nav>
        \\
    );
    portal(allocator, w, "meta.nav", false) catch {}; // ignore error
    try w.writeAll(
        \\</nav>
        \\</header>
        \\
    );

    // MAIN
    try w.print(
        \\<main>
        \\
    , .{});
    try inject(allocator, w, srcpath);
    try w.writeAll(
        \\</main>
        \\
    );

    // FOOTER
    try w.print(
        \\<footer>
        \\Edited on {[MTIME]s} <a href="{[SOURCE_URL]s}/{[PATH]s}" target="_blank">[src]</a>
        \\<a href="mailto:{[PUBLIC_INBOX]s}">[comments]</a>
        \\<br>
        \\<b>{[LICENSE_HOLDER]s}</b>
        \\&copy; {[LICENSE_YEAR]s}
        \\&mdash;
        \\<a href="{[LICENSE_URL]s}" target="_blank">{[LICENSE_NAME]s}</a>
        \\</footer>
        \\
    , .{
        .LICENSE_HOLDER = Context.params.LICENSE_HOLDER,
        .LICENSE_NAME = Context.params.LICENSE_NAME,
        .LICENSE_URL = Context.params.LICENSE_URL,
        .LICENSE_YEAR = Context.params.LICENSE_YEAR,
        .MTIME = mtime_str,
        .PATH = srcpath,
        .PUBLIC_INBOX = Context.params.PUBLIC_INBOX,
        .SOURCE_URL = Context.params.SOURCE_URL,
    });

    try w.writeAll(
        \\<a href="#top">[&#9206;]</a>
        \\
    );

    try w.writeAll(
        \\</body>
        \\</html>
        \\
    );

    try w.flush();
}

// build a virtual html file, currently either:
// - meta.nav: used for populating the global navigation menu
// - meta.tilde: used to create ~foobar files
fn meta(ctx: *Context, p: []const u8) !void {
    ctx.meta += 1;

    if (std.mem.startsWith(u8, p, "meta.nav.")) return;

    if (std.mem.startsWith(u8, p, "meta.tilde.")) {
        const dot = std.mem.indexOfPosLinear(u8, p, 11, ".");
        const dstname = p[11..dot.?];
        const srcpath = try fs.joinPathAndFilename(ctx.allocator(), &.{Context.params.PAGE_PATH}, &.{p});
        defer ctx.allocator().free(srcpath);
        const dstpath = try fs.joinPathAndFilename(ctx.allocator(), &.{Context.params.LINK_PATH}, &.{ "~", dstname });
        defer ctx.allocator().free(dstpath);

        const link = blk: {
            const f = try std.fs.cwd().openFile(srcpath, .{ .mode = .read_only });
            defer f.close();
            const content = try f.readToEndAlloc(ctx.allocator(), std.os.linux.PATH_MAX);
            defer ctx.allocator().free(content);
            const trimmed = std.mem.trim(u8, content, " \n\t\r");
            break :blk try ctx.allocator().dupe(u8, trimmed);
        };
        defer ctx.allocator().free(link);

        const f = try fs.FileSwapper.createAt(ctx.allocator(), dstpath);
        defer f.close();

        var buffer: [1024]u8 = undefined;
        var w = f.writer(&buffer);

        try w.interface.print(
            \\<!DOCTYPE html>
            \\<html lang="en">
            \\<head>
            \\<meta charset="utf-8">
            \\<meta http-equiv="refresh" content="0; url={[LINK]s}">
            \\<meta name="fediverse:creator" content="@robertgzr@toot.berlin">
            \\<link rel="stylesheet" type="text/css" href="links/main.css">
            \\</head>
            \\<body>
            \\<noscript>Continue to <a href="{[LINK]s}">{[LINK]s}</a>.</noscript>
            \\<script>
            \\'use strict'
            \\window.location.replace("{[LINK]s}")
            \\</script>
            \\</body>
            \\</html>
            \\
        , .{
            .LINK = link,
        });
        try w.interface.flush();

        ctx.tilde += 1;
        return;
    }

    return error.unknownMeta;
}

// parses srcpath, resolves refs and portals and writes everything to w
fn inject(allocator: std.mem.Allocator, w: *std.Io.Writer, srcpath: []const u8) !void {
    var arena = std.heap.ArenaAllocator.init(allocator);
    defer arena.deinit();

    const inc = std.fs.cwd().openFile(srcpath, .{ .mode = .read_only }) catch |err| {
        if (err == error.FileNotFound)
            log.warn("Missing {s} include.", .{srcpath});

        return err;
    };
    defer inc.close();

    var buffer: [1024]u8 = undefined;
    var r = inc.readerStreaming(&buffer);

    var chunkw = std.Io.Writer.Allocating.init(arena.allocator());
    defer chunkw.deinit();

    while (true) {
        defer chunkw.clearRetainingCapacity(); // reset chunk

        _ = r.interface.streamDelimiter(&chunkw.writer, '\n') catch |err|
            if (err == error.EndOfStream) break
            else return err;

        _ = r.interface.toss(1); // skip newline delimiter

        var chunk = chunkw.written();
        templating: while (true) {
            if (std.mem.indexOfPosLinear(u8, chunk, 0, "{")) |start| {
                if (std.mem.indexOfPosLinear(u8, chunk, start + 1, "}")) |end| {
                    try w.writeAll(chunk[0..start]);
                    template(allocator, w, chunk[start + 1 .. end]) catch |err| switch (err) {
                        error.FileNotFound => {
                            // log.warn("ref {s} not found", .{chunk[start + 1 .. end]});
                            // trim already written chunk and exit templating
                            chunk = chunk[start..];
                            break :templating;
                        },
                        else => @panic("Failed to resolve template"),
                    };
                    chunk = chunk[end + 1 ..];
                } else break :templating;
            } else break :templating;
        }

        try w.writeAll(chunk);
        try w.writeByte('\n');
        try w.flush();
    }

    try w.flush();
}

// implements various reference types that can be used in .htm templates
fn template(allocator: std.mem.Allocator, w: *std.Io.Writer, refname: []const u8) anyerror!void {
    switch (refname[0]) {
        '/' => return try portal(allocator, w, refname[1..], false),
        '$' => return try ref_link(allocator, w, refname[1..]),
        '+' => return try ref_name(allocator, w, refname[1..]),
        else => return try ref(allocator, w, refname),
    }
}

const Page = struct {
    arena: std.heap.ArenaAllocator,
    ref: []const u8,
    name: []const u8,
    html: []const u8,
    htm: []const u8,
    anchor: []const u8,

    fn from_ref(allocator: std.mem.Allocator, refname: []const u8) !Page {
        var arena = std.heap.ArenaAllocator.init(allocator);

        const endofref = std.mem.lastIndexOf(u8, refname, "#") orelse refname.len;
        const basename = try std.mem.replaceOwned(u8, arena.allocator(), refname[0..endofref], " ", "_");
        const html = try fs.joinPathAndFilename(arena.allocator(), &.{Context.params.SITE_PATH}, &.{ basename, ".html" });
        const htm = try fs.joinPathAndFilename(arena.allocator(), &.{Context.params.PAGE_PATH}, &.{ basename, ".htm" });

        try std.fs.cwd().access(htm, .{ .mode = .read_only });

        return .{
            .arena = arena,
            .ref = refname[0..endofref],
            .name = basename,
            .html = html,
            .htm = htm,
            .anchor = if (endofref < refname.len) refname[endofref..] else "",
        };
    }

    fn deinit(self: Page) void {
        self.arena.deinit();
    }
};

fn portal(allocator: std.mem.Allocator, w: *std.Io.Writer, refname: []const u8, insert_heading: bool) anyerror!void {
    const page = try Page.from_ref(allocator, refname);
    defer page.deinit();

    if (insert_heading)
        try w.print(
            \\<h2 id="{[ID]s}"><a href="/{[PATH]s}">{[NAME]s}</a></2>
            \\
        , .{
            .ID = page.ref,
            .NAME = page.name,
            .PATH = page.html,
        });

    try inject(allocator, w, page.htm);

    // XXX: track ref count?
}

fn ref(allocator: std.mem.Allocator, w: *std.Io.Writer, refname: []const u8) anyerror!void {
    const page = try Page.from_ref(allocator, refname);
    defer page.deinit();

    try w.print(
        \\<a href="/{[PATH]s}{[ANCHOR]s}">{[NAME]s}</a>
    , .{
        .NAME = page.name,
        .PATH = page.html,
        .ANCHOR = page.anchor,
    });

    // XXX: track ref count?
}

fn ref_link(allocator: std.mem.Allocator, w: *std.Io.Writer, refname: []const u8) anyerror!void {
    const page = try Page.from_ref(allocator, refname);
    defer page.deinit();

    try w.print("/{s}{s}", .{ page.html, page.anchor });
}

fn ref_name(allocator: std.mem.Allocator, w: *std.Io.Writer, refname: []const u8) anyerror!void {
    const page = try Page.from_ref(allocator, refname);
    defer page.deinit();

    try w.print("{s}", .{page.ref});
}