//! Staleness nags for hand-maintained data sources.
//!
//! Some datasets in this codebase require periodic human maintenance
//! (e.g. appending the latest year's T-bill rate, replacing Shiller's
//! `ie_data.csv`). Each such source declares a `pub const <name>_last_updated: Date`
//! constant which a human bumps when the refresh happens.
//!
//! This module registers those sources and prints a warning to stderr
//! on every `zfin` invocation once the annual refresh window opens
//! and the data is still stale. The refresh window is expressed as a
//! single `(month, day)` per year — the earliest date by which fresh
//! upstream data is expected to be available — not as a rolling
//! day-count.
//!
//! ### Nagging semantics
//!
//! Given today's date and an entry's `(due_month, due_day, last_updated)`:
//!
//! 1. Compute `this_years_due = Date.fromYmd(today.year(), due_month, due_day)`.
//! 2. If `today < this_years_due` — not yet nag season, silent.
//! 3. If `last_updated >= this_years_due` — already refreshed this cycle, silent.
//! 4. Otherwise — nag.
//!
//! The nag keeps firing every invocation until the human bumps
//! `last_updated` past `this_years_due`.
//!
//! ### Adding a new source
//!
//! 1. Add `pub const <name>_last_updated: Date = Date.fromYmd(YYYY, MM, DD);`
//!    to the module that owns the data.
//! 2. Append a new `StaleEntry` to `entries` below.
//! 3. Document the refresh procedure in the owning module's doc
//!    comment (or a `TODO` at the top).

const std = @import("std");
const Date = @import("../models/date.zig").Date;
const risk = @import("../analytics/risk.zig");
const shiller = @import("shiller.zig");

/// A hand-maintained data source that nags once a year if it hasn't
/// been refreshed by its annual `(due_month, due_day)`.
pub const StaleEntry = struct {
    /// Human-readable name surfaced in the warning.
    name: []const u8,
    /// The last time a human refreshed this data. Bumped by hand.
    last_updated: Date,
    /// Calendar month (1-12) by which fresh upstream data is expected.
    due_month: u8,
    /// Calendar day (1-31) within `due_month`.
    due_day: u8,
    /// Source file to point the user at for refresh instructions.
    source_file: []const u8,
};

/// Registry of hand-maintained data sources in this codebase. Passed
/// to `check` from `main.zig`; tests construct their own slices.
pub const entries = [_]StaleEntry{
    .{
        .name = "T-bill risk-free rate table",
        .last_updated = risk.tbill_rates_last_updated,
        .due_month = 1,
        .due_day = 31,
        .source_file = "src/analytics/risk.zig",
    },
    .{
        .name = "Shiller annual returns (ie_data.csv)",
        .last_updated = shiller.ie_data_last_updated,
        .due_month = 4,
        .due_day = 1,
        .source_file = "src/data/shiller.zig",
    },
};

/// Write a warning line for each entry in `entries` that is overdue
/// for refresh as of `as_of`. Writes nothing when every entry is
/// fresh. Entries are processed in order; multiple warnings are
/// separated by a blank line.
pub fn check(
    writer: *std.Io.Writer,
    as_of: Date,
    list: []const StaleEntry,
) !void {
    var wrote_any = false;
    for (list) |entry| {
        const this_years_due = Date.fromYmd(
            as_of.year(),
            entry.due_month,
            entry.due_day,
        );
        // Not yet nag season.
        if (as_of.lessThan(this_years_due)) continue;
        // Already refreshed this cycle.
        if (!entry.last_updated.lessThan(this_years_due)) continue;

        if (wrote_any) try writer.writeAll("\n");
        wrote_any = true;

        var due_buf: [10]u8 = undefined;
        var upd_buf: [10]u8 = undefined;
        const due_str = this_years_due.format(&due_buf);
        const upd_str = entry.last_updated.format(&upd_buf);

        try writer.print(
            "warning: {s} is overdue for refresh.\n" ++
                "  Expected by {s}; last updated {s}.\n" ++
                "  See {s} for refresh instructions.\n",
            .{ entry.name, due_str, upd_str, entry.source_file },
        );
    }
}

// ── Tests ────────────────────────────────────────────────────

test "silent before due date" {
    var buf: [1024]u8 = undefined;
    var w = std.Io.Writer.fixed(&buf);
    const list = [_]StaleEntry{.{
        .name = "Test data",
        .last_updated = Date.fromYmd(2025, 3, 15),
        .due_month = 4,
        .due_day = 1,
        .source_file = "src/test.zig",
    }};
    try check(&w, Date.fromYmd(2026, 3, 31), &list);
    try std.testing.expectEqualStrings("", w.buffered());
}

test "nag on due date when stale" {
    var buf: [1024]u8 = undefined;
    var w = std.Io.Writer.fixed(&buf);
    const list = [_]StaleEntry{.{
        .name = "Test data",
        .last_updated = Date.fromYmd(2025, 3, 15),
        .due_month = 4,
        .due_day = 1,
        .source_file = "src/test.zig",
    }};
    try check(&w, Date.fromYmd(2026, 4, 1), &list);
    const expected =
        "warning: Test data is overdue for refresh.\n" ++
        "  Expected by 2026-04-01; last updated 2025-03-15.\n" ++
        "  See src/test.zig for refresh instructions.\n";
    try std.testing.expectEqualStrings(expected, w.buffered());
}

test "nag after due date when stale" {
    var buf: [1024]u8 = undefined;
    var w = std.Io.Writer.fixed(&buf);
    const list = [_]StaleEntry{.{
        .name = "Test data",
        .last_updated = Date.fromYmd(2025, 3, 15),
        .due_month = 4,
        .due_day = 1,
        .source_file = "src/test.zig",
    }};
    try check(&w, Date.fromYmd(2026, 6, 15), &list);
    const expected =
        "warning: Test data is overdue for refresh.\n" ++
        "  Expected by 2026-04-01; last updated 2025-03-15.\n" ++
        "  See src/test.zig for refresh instructions.\n";
    try std.testing.expectEqualStrings(expected, w.buffered());
}

test "silent when already refreshed this cycle" {
    var buf: [1024]u8 = undefined;
    var w = std.Io.Writer.fixed(&buf);
    const list = [_]StaleEntry{.{
        .name = "Test data",
        .last_updated = Date.fromYmd(2026, 4, 2),
        .due_month = 4,
        .due_day = 1,
        .source_file = "src/test.zig",
    }};
    try check(&w, Date.fromYmd(2026, 6, 15), &list);
    try std.testing.expectEqualStrings("", w.buffered());
}

test "silent when last_updated equals this year's due date" {
    var buf: [1024]u8 = undefined;
    var w = std.Io.Writer.fixed(&buf);
    const list = [_]StaleEntry{.{
        .name = "Test data",
        .last_updated = Date.fromYmd(2026, 4, 1),
        .due_month = 4,
        .due_day = 1,
        .source_file = "src/test.zig",
    }};
    try check(&w, Date.fromYmd(2026, 4, 1), &list);
    try std.testing.expectEqualStrings("", w.buffered());
}

test "two-cycle stale still fires" {
    var buf: [1024]u8 = undefined;
    var w = std.Io.Writer.fixed(&buf);
    const list = [_]StaleEntry{.{
        .name = "Test data",
        .last_updated = Date.fromYmd(2024, 2, 1),
        .due_month = 4,
        .due_day = 1,
        .source_file = "src/test.zig",
    }};
    try check(&w, Date.fromYmd(2026, 6, 15), &list);
    const expected =
        "warning: Test data is overdue for refresh.\n" ++
        "  Expected by 2026-04-01; last updated 2024-02-01.\n" ++
        "  See src/test.zig for refresh instructions.\n";
    try std.testing.expectEqualStrings(expected, w.buffered());
}

test "empty list is a no-op" {
    var buf: [16]u8 = undefined;
    var w = std.Io.Writer.fixed(&buf);
    try check(&w, Date.fromYmd(2030, 12, 31), &[_]StaleEntry{});
    try std.testing.expectEqualStrings("", w.buffered());
}

test "multiple stale entries separated by blank line" {
    var buf: [2048]u8 = undefined;
    var w = std.Io.Writer.fixed(&buf);
    const list = [_]StaleEntry{
        .{
            .name = "Alpha",
            .last_updated = Date.fromYmd(2024, 12, 1),
            .due_month = 1,
            .due_day = 31,
            .source_file = "src/alpha.zig",
        },
        .{
            .name = "Beta",
            .last_updated = Date.fromYmd(2025, 3, 15),
            .due_month = 4,
            .due_day = 1,
            .source_file = "src/beta.zig",
        },
    };
    try check(&w, Date.fromYmd(2026, 6, 15), &list);
    const expected =
        "warning: Alpha is overdue for refresh.\n" ++
        "  Expected by 2026-01-31; last updated 2024-12-01.\n" ++
        "  See src/alpha.zig for refresh instructions.\n" ++
        "\n" ++
        "warning: Beta is overdue for refresh.\n" ++
        "  Expected by 2026-04-01; last updated 2025-03-15.\n" ++
        "  See src/beta.zig for refresh instructions.\n";
    try std.testing.expectEqualStrings(expected, w.buffered());
}

test "fresh entry does not emit blank line before later stale entry" {
    var buf: [2048]u8 = undefined;
    var w = std.Io.Writer.fixed(&buf);
    const list = [_]StaleEntry{
        .{
            .name = "Alpha",
            .last_updated = Date.fromYmd(2026, 2, 1), // fresh
            .due_month = 1,
            .due_day = 31,
            .source_file = "src/alpha.zig",
        },
        .{
            .name = "Beta",
            .last_updated = Date.fromYmd(2025, 3, 15), // stale
            .due_month = 4,
            .due_day = 1,
            .source_file = "src/beta.zig",
        },
    };
    try check(&w, Date.fromYmd(2026, 6, 15), &list);
    const expected =
        "warning: Beta is overdue for refresh.\n" ++
        "  Expected by 2026-04-01; last updated 2025-03-15.\n" ++
        "  See src/beta.zig for refresh instructions.\n";
    try std.testing.expectEqualStrings(expected, w.buffered());
}

test "silent when today is one day before due" {
    var buf: [256]u8 = undefined;
    var w = std.Io.Writer.fixed(&buf);
    const list = [_]StaleEntry{.{
        .name = "Test data",
        .last_updated = Date.fromYmd(2020, 1, 1),
        .due_month = 4,
        .due_day = 1,
        .source_file = "src/test.zig",
    }};
    try check(&w, Date.fromYmd(2026, 3, 31), &list);
    try std.testing.expectEqualStrings("", w.buffered());
}

test "real registry compiles and is non-empty" {
    // Guard that the registry stays wired up; doesn't assert any
    // particular nag behavior (real dates drift over time).
    try std.testing.expect(entries.len >= 2);
    for (entries) |e| {
        try std.testing.expect(e.name.len > 0);
        try std.testing.expect(e.source_file.len > 0);
        try std.testing.expect(e.due_month >= 1 and e.due_month <= 12);
        try std.testing.expect(e.due_day >= 1 and e.due_day <= 31);
    }
}