//! Wikidata SPARQL classification provider.
//!
//! ## What this provider does
//!
//! Given a stock symbol, Wikidata can answer:
//!
//!   * "What kind of entity is this?" — name, industry, sector,
//!     country of incorporation, inception date, instance-of
//!     classification (operating company / mutual fund / ETF / …).
//!   * "Does this match the SEC's CIK?" — Wikidata's P5531 already
//!     stores the 10-digit zero-padded CIK matching SEC's convention.
//!
//! ## Workflow
//!
//! `fetch(symbols)` runs ONE batched SPARQL query that returns
//! per-ticker rows. The query is keyed on the US-listing (NYSE /
//! Nasdaq / NYSE Arca / OTC Markets) of each ticker — without that
//! filter, common US tickers silently resolve to whichever
//! foreign-exchange company happens to share the symbol (`MRK` →
//! Merck KGaA on Frankfurt; `PG` → People's Garment on SET; etc.).
//!
//! The provider is stateless. Caching belongs to the data service,
//! which writes per-symbol `classification.srf` files after this
//! provider returns and reads them back on subsequent calls.
//!
//! ## Glossary
//!
//!   SPARQL    Query language for RDF-shaped data. Wikidata's
//!             primary read API.
//!   P-number  Property identifier in Wikidata (P249 = ticker symbol,
//!             P414 = stock exchange, P31 = instance of, ...).
//!   Q-number  Entity identifier in Wikidata (Q40244 = ETF as a
//!             concept, Q13677 = NYSE the entity, Q312 = Apple Inc.
//!             the entity).
//!   wdt:Pxxx  Truthy/direct property statement — the simple shape.
//!   p:Pxxx    Reified property statement — lets a statement carry
//!             qualifiers (e.g. ticker symbol AS A QUALIFIER on the
//!             stock-exchange statement, rather than as a direct
//!             property of the company).
//!   ps:Pxxx   "Statement value" predicate — within a reified
//!             statement, points to the statement's main value.
//!   pq:Pxxx   "Qualifier" predicate — within a reified statement,
//!             points to a qualifier on that statement.
//!
//! Why the reified statement matters here: Wikidata stores tickers
//! as P249 qualifiers on a P414 (stock exchange) statement, NOT as
//! a direct `wdt:P249` property. Querying naively returns zero rows
//! for nearly every US-listed equity.

const std = @import("std");
const http = @import("../net/http.zig");
const fmt = @import("../format.zig");

const sparql_endpoint = "https://query.wikidata.org/sparql";

/// Per-symbol classification record produced by parsing a Wikidata
/// SPARQL response. Fields are nullable when Wikidata has no value
/// for that property; the `source` field always emits per the
/// project's source-pure invariant.
pub const ClassificationRecord = struct {
    symbol: []const u8, // owned
    name: ?[]const u8 = null, // owned
    sector: ?[]const u8 = null, // owned
    industry: ?[]const u8 = null, // owned
    /// ISO-3166 alpha-2 country code (e.g. "US", "GB", "DE").
    country: ?[]const u8 = null, // owned
    asset_class: ?[]const u8 = null, // owned
    is_etf: bool = false,
    /// YYYY-MM-DD; trimmed from Wikidata's ISO-8601 date.
    inception_date: ?[]const u8 = null, // owned
    /// Wikidata's P5531 — the SEC CIK as a digit string. Wikidata
    /// already zero-pads to 10 digits, matching the project-wide
    /// CIK normalization convention.
    cik: ?[]const u8 = null, // owned
    /// YYYY-MM-DD when this provider ran, NOT when Wikidata last
    /// updated the underlying entity.
    as_of: []const u8, // owned
    source: []const u8, // no default — provenance always emitted

    pub fn deinit(self: *ClassificationRecord, allocator: std.mem.Allocator) void {
        allocator.free(self.symbol);
        if (self.name) |s| allocator.free(s);
        if (self.sector) |s| allocator.free(s);
        if (self.industry) |s| allocator.free(s);
        if (self.country) |s| allocator.free(s);
        if (self.asset_class) |s| allocator.free(s);
        if (self.inception_date) |s| allocator.free(s);
        if (self.cik) |s| allocator.free(s);
        allocator.free(self.as_of);
    }
};

/// Geo-bucket constants used by the country → geo lookup. Kept as
/// named constants (rather than inline string literals in the map)
/// so callers can reference them without typo risk and the
/// taxonomy is tweakable in one place.
pub const geo = struct {
    pub const us = "US";
    pub const developed = "International Developed";
    pub const emerging = "Emerging Markets";
    pub const unknown = "Unknown";
};

/// Wikidata Q-IDs we test against `instance of` (P31) to classify
/// fund-shaped securities. Curated, not exhaustive.
const etf_q_ids = [_][]const u8{
    "Q40244", // exchange-traded fund
    "Q4118901", // exchange-traded bond fund
    "Q104638128", // ETF tracking specific index
};
const mutual_fund_q_ids = [_][]const u8{
    "Q1752230", // mutual fund
    "Q11644608", // open-end fund
};

/// US stock exchanges accepted by the SPARQL exchange filter.
/// Without this filter, ticker collisions across global exchanges
/// silently return the wrong company.
///
/// Q-IDs:
///   Q13677     New York Stock Exchange (NYSE)
///   Q82059     Nasdaq
///   Q4527260   NYSE Arca
///   Q1666011   OTC Markets Group / Pink Sheets
const us_exchanges = [_][]const u8{
    "wd:Q13677",
    "wd:Q82059",
    "wd:Q4527260",
    "wd:Q1666011",
};

/// Country-code-to-geo-bucket lookup. Wikidata returns ISO-3166
/// alpha-2 codes via P17 → P297; we map them to the geo taxonomy
/// (`geo.us` / `geo.developed` / `geo.emerging` / `geo.unknown`).
///
/// MSCI conventions used as the developed/emerging split. Taiwan
/// and South Korea are MSCI-emerging despite FTSE classifying them
/// developed. Israel is MSCI-developed (upgraded 2010). Canada is
/// folded into International Developed (some users prefer separate
/// Canada bucket; override in `metadata.srf` if so).
const country_to_geo = std.StaticStringMap([]const u8).initComptime(.{
    // United States
    .{ "US", geo.us },
    // Alpha-3 fallback for entries that use the longer form.
    .{ "USA", geo.us },

    // International Developed — Europe ex-CIS
    .{ "GB", geo.developed },
    .{ "DE", geo.developed },
    .{ "FR", geo.developed },
    .{ "NL", geo.developed },
    .{ "CH", geo.developed },
    .{ "SE", geo.developed },
    .{ "DK", geo.developed },
    .{ "NO", geo.developed },
    .{ "FI", geo.developed },
    .{ "IT", geo.developed },
    .{ "ES", geo.developed },
    .{ "BE", geo.developed },
    .{ "AT", geo.developed },
    .{ "IE", geo.developed },
    .{ "LU", geo.developed },
    .{ "PT", geo.developed },
    .{ "GR", geo.developed },
    .{ "IS", geo.developed },

    // International Developed — Asia-Pacific + Israel + Canada
    .{ "JP", geo.developed },
    .{ "AU", geo.developed },
    .{ "NZ", geo.developed },
    .{ "SG", geo.developed },
    .{ "HK", geo.developed },
    .{ "IL", geo.developed },
    .{ "CA", geo.developed },

    // Emerging Markets (MSCI)
    .{ "CN", geo.emerging },
    .{ "TW", geo.emerging },
    .{ "KR", geo.emerging },
    .{ "IN", geo.emerging },
    .{ "BR", geo.emerging },
    .{ "MX", geo.emerging },
    .{ "RU", geo.emerging },
    .{ "TR", geo.emerging },
    .{ "ZA", geo.emerging },
    .{ "TH", geo.emerging },
    .{ "MY", geo.emerging },
    .{ "ID", geo.emerging },
    .{ "PH", geo.emerging },
    .{ "VN", geo.emerging },
    .{ "AR", geo.emerging },
    .{ "CL", geo.emerging },
    .{ "CO", geo.emerging },
    .{ "PE", geo.emerging },
    .{ "EG", geo.emerging },
});

/// Map an ISO-3166 alpha-2 country code to one of the geo buckets.
/// Null/empty input or an unknown code returns `geo.unknown` so the
/// user can override in `metadata.srf`.
pub fn geoFor(iso2: ?[]const u8) []const u8 {
    const code = iso2 orelse return geo.unknown;
    if (code.len == 0) return geo.unknown;
    return country_to_geo.get(code) orelse geo.unknown;
}

// ── Wikidata provider state (file-as-struct) ─────────────────────
//
// Callers do `const wikidata = @import("providers/Wikidata.zig");`
// followed by `var wd = wikidata.init(...);` and `wd.fetch(...)`.

client: http.Client,
allocator: std.mem.Allocator,
io: std.Io,
/// Contact email for User-Agent / From headers, sourced from
/// `Config.user_email`. Required; callers must surface a clear
/// missing-config error before constructing this provider.
user_email: []const u8,

const Wikidata = @This();

pub fn init(
    io: std.Io,
    allocator: std.mem.Allocator,
    user_email: []const u8,
) Wikidata {
    return .{
        .client = http.Client.init(io, allocator),
        .allocator = allocator,
        .io = io,
        .user_email = user_email,
    };
}

pub fn deinit(self: *Wikidata) void {
    self.client.deinit();
}

/// Fetch and parse Wikidata classifications for `symbols`.
/// Runs a single batched SPARQL query and parses the response.
/// Caller owns the returned slice and each record.
pub fn fetch(
    self: *Wikidata,
    result_allocator: std.mem.Allocator,
    symbols: []const []const u8,
) ![]ClassificationRecord {
    if (symbols.len == 0) return &.{};

    const query = try buildQuery(self.allocator, symbols);
    defer self.allocator.free(query);

    const json = try self.postSparql(query);
    defer self.allocator.free(json);

    return parse(self.io, result_allocator, json, symbols);
}

/// POST a SPARQL query. Sets the User-Agent + From headers from
/// `user_email` for politeness; Wikidata explicitly recommends
/// descriptive User-Agent strings.
fn postSparql(self: *Wikidata, query: []const u8) ![]u8 {
    var form_buf: std.Io.Writer.Allocating = .init(self.allocator);
    defer form_buf.deinit();
    try form_buf.writer.writeAll("query=");
    // `Component.formatEscaped` percent-encodes everything outside
    // RFC 3986's unreserved set — exactly the contract for the
    // `application/x-www-form-urlencoded` body we're building.
    try (std.Uri.Component{ .raw = query }).formatEscaped(&form_buf.writer);

    var ua_buf: [256]u8 = undefined;
    const ua = std.fmt.bufPrint(&ua_buf, "zfin/0.1 ({s})", .{self.user_email}) catch return error.UserEmailTooLong;

    const headers = [_]std.http.Header{
        .{ .name = "User-Agent", .value = ua },
        .{ .name = "Accept", .value = "application/sparql-results+json" },
        .{ .name = "Content-Type", .value = "application/x-www-form-urlencoded" },
        .{ .name = "From", .value = self.user_email },
    };

    var resp = try self.client.request(.POST, sparql_endpoint, form_buf.written(), &headers);
    defer resp.deinit();
    return self.allocator.dupe(u8, resp.body);
}

/// Build the batched SPARQL query for a slice of ticker symbols.
/// Caller owns the returned bytes. Symbols interpolated via
/// `VALUES ?ticker { "AAPL" "MSFT" ... }`.
///
/// Wikidata's ticker storage is non-obvious: tickers are stored as
/// `P249` qualifiers on a `P414` (stock exchange) statement. Naive
/// `?security wdt:P249 ?ticker` returns zero rows for nearly every
/// US-listed equity. The query reaches them via:
///
///   ?security p:P414 ?stmt .
///   ?stmt ps:P414 ?exchange .
///   ?stmt pq:P249 ?ticker .
///
/// `?exchange` is filtered to a small set of US exchanges to avoid
/// ticker collisions with foreign listings.
fn buildQuery(allocator: std.mem.Allocator, symbols: []const []const u8) ![]u8 {
    var aw: std.Io.Writer.Allocating = .init(allocator);
    defer aw.deinit();

    try aw.writer.writeAll(
        \\SELECT ?ticker ?security ?securityLabel ?industryLabel ?countryCode ?inception ?cik ?instance WHERE {
        \\  VALUES ?ticker {
    );
    for (symbols) |s| {
        try aw.writer.print(" \"{s}\"", .{s});
    }
    try aw.writer.writeAll(" }\n");
    try aw.writer.writeAll("  VALUES ?exchange {");
    for (us_exchanges) |x| {
        try aw.writer.print(" {s}", .{x});
    }
    try aw.writer.writeAll(" }\n");
    try aw.writer.writeAll(
        \\  ?security p:P414 ?exchstmt .
        \\  ?exchstmt ps:P414 ?exchange .
        \\  ?exchstmt pq:P249 ?ticker .
        \\  OPTIONAL { ?security wdt:P452 ?industry . }
        \\  OPTIONAL { ?security wdt:P17 ?country . ?country wdt:P297 ?countryCode . }
        \\  OPTIONAL { ?security wdt:P571 ?inception . }
        \\  OPTIONAL { ?security wdt:P5531 ?cik . }
        \\  OPTIONAL { ?security wdt:P31 ?instance . }
        \\  SERVICE wikibase:label { bd:serviceParam wikibase:language "en". }
        \\}
    );
    return aw.toOwnedSlice();
}

/// Parse the SPARQL JSON response into `ClassificationRecord` values.
/// Multiple bindings for the same ticker (e.g. multiple `instance of`
/// values) get merged into one record — first-non-null wins.
fn parse(
    io: std.Io,
    allocator: std.mem.Allocator,
    json_bytes: []const u8,
    expected_symbols: []const []const u8,
) ![]ClassificationRecord {
    const today = fmt.todayDate(io);
    var as_of_buf: [10]u8 = undefined;
    const as_of = try std.fmt.bufPrint(&as_of_buf, "{f}", .{today});

    const parsed = std.json.parseFromSlice(std.json.Value, allocator, json_bytes, .{}) catch
        return &.{};
    defer parsed.deinit();

    const root = switch (parsed.value) {
        .object => |o| o,
        else => return &.{},
    };
    const results = switch (root.get("results") orelse return &.{}) {
        .object => |o| o,
        else => return &.{},
    };
    const bindings = switch (results.get("bindings") orelse return &.{}) {
        .array => |a| a.items,
        else => return &.{},
    };

    // Map symbol → record; merge multiple bindings.
    var by_symbol: std.StringHashMap(ClassificationRecord) = .init(allocator);
    defer {
        var it = by_symbol.valueIterator();
        while (it.next()) |r| r.deinit(allocator);
        by_symbol.deinit();
    }

    for (bindings) |b| {
        const obj = switch (b) {
            .object => |o| o,
            else => continue,
        };
        const ticker = sparqlValue(obj, "ticker") orelse continue;

        // Verify ticker is one we asked for. Wikidata can return
        // surprising matches (foreign exchanges); skip those.
        var matched = false;
        for (expected_symbols) |s| {
            if (std.ascii.eqlIgnoreCase(s, ticker)) {
                matched = true;
                break;
            }
        }
        if (!matched) continue;

        const existing_or_new = try by_symbol.getOrPut(ticker);
        if (!existing_or_new.found_existing) {
            existing_or_new.key_ptr.* = try allocator.dupe(u8, ticker);
            existing_or_new.value_ptr.* = .{
                .symbol = try allocator.dupe(u8, ticker),
                .as_of = try allocator.dupe(u8, as_of),
                .source = "wikidata",
            };
        }
        const rec = existing_or_new.value_ptr;

        if (rec.name == null) {
            if (sparqlValue(obj, "securityLabel")) |label| {
                rec.name = try allocator.dupe(u8, label);
            }
        }
        if (rec.industry == null) {
            if (sparqlValue(obj, "industryLabel")) |ind| {
                rec.industry = try allocator.dupe(u8, ind);
                rec.sector = try allocator.dupe(u8, ind);
            }
        }
        if (rec.country == null) {
            if (sparqlValue(obj, "countryCode")) |c| {
                rec.country = try allocator.dupe(u8, c);
            }
        }
        if (rec.inception_date == null) {
            if (sparqlValue(obj, "inception")) |d| {
                if (d.len >= 10) {
                    rec.inception_date = try allocator.dupe(u8, d[0..10]);
                }
            }
        }
        if (rec.cik == null) {
            if (sparqlValue(obj, "cik")) |c| {
                rec.cik = try allocator.dupe(u8, c);
            }
        }
        if (sparqlValue(obj, "instance")) |inst_iri| {
            // The "instance" value is a Q-ID URI like
            // "http://www.wikidata.org/entity/Q40244". Extract the
            // Q-ID suffix and test against our known sets.
            const last_slash = std.mem.lastIndexOfScalar(u8, inst_iri, '/');
            const q_id = if (last_slash) |i| inst_iri[i + 1 ..] else inst_iri;
            for (etf_q_ids) |target| {
                if (std.mem.eql(u8, q_id, target)) {
                    rec.is_etf = true;
                    if (rec.asset_class == null) {
                        rec.asset_class = try allocator.dupe(u8, "ETF (uncategorized)");
                    }
                    break;
                }
            }
            for (mutual_fund_q_ids) |target| {
                if (std.mem.eql(u8, q_id, target)) {
                    rec.is_etf = true;
                    if (rec.asset_class == null) {
                        rec.asset_class = try allocator.dupe(u8, "Mutual Fund (uncategorized)");
                    }
                    break;
                }
            }
        }
    }

    // Drain map into owned slice. Caller takes ownership; our defer
    // above calls deinit on values, so clear the map before returning
    // to avoid double-free.
    var out = try allocator.alloc(ClassificationRecord, by_symbol.count());
    var idx: usize = 0;
    var it = by_symbol.iterator();
    while (it.next()) |entry| {
        out[idx] = entry.value_ptr.*;
        idx += 1;
    }
    var key_it = by_symbol.keyIterator();
    while (key_it.next()) |k| allocator.free(k.*);
    by_symbol.clearRetainingCapacity();
    return out;
}

/// Pull the `.value` string out of a SPARQL JSON binding object's
/// named field. Returns null if absent or non-string.
fn sparqlValue(obj: std.json.ObjectMap, field: []const u8) ?[]const u8 {
    const slot = obj.get(field) orelse return null;
    const slot_obj = switch (slot) {
        .object => |o| o,
        else => return null,
    };
    const val = slot_obj.get("value") orelse return null;
    return switch (val) {
        .string => |s| s,
        else => null,
    };
}

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

test "buildQuery includes all symbols and required SELECT vars" {
    const allocator = std.testing.allocator;
    const syms = [_][]const u8{ "AAPL", "VTI" };
    const q = try buildQuery(allocator, &syms);
    defer allocator.free(q);

    try std.testing.expect(std.mem.indexOf(u8, q, "\"AAPL\"") != null);
    try std.testing.expect(std.mem.indexOf(u8, q, "\"VTI\"") != null);
    try std.testing.expect(std.mem.indexOf(u8, q, "p:P414") != null);
    try std.testing.expect(std.mem.indexOf(u8, q, "pq:P249") != null);
    try std.testing.expect(std.mem.indexOf(u8, q, "wdt:P452") != null);
    try std.testing.expect(std.mem.indexOf(u8, q, "wdt:P17") != null);
    // US-exchange filter must be present — without it, US tickers
    // collide with foreign exchanges (MRK→Merck KGaA, PG→People's
    // Garment, etc.). See `us_exchanges` doc-block.
    try std.testing.expect(std.mem.indexOf(u8, q, "wd:Q13677") != null); // NYSE
    try std.testing.expect(std.mem.indexOf(u8, q, "wd:Q82059") != null); // Nasdaq
    try std.testing.expect(std.mem.indexOf(u8, q, "ps:P414 ?exchange") != null);
}

test "parse: AAPL fixture round-trips name + industry + country" {
    const fixture =
        \\{
        \\  "head": {"vars": ["ticker", "security", "securityLabel", "industryLabel", "countryCode", "inception", "cik", "instance"]},
        \\  "results": {
        \\    "bindings": [
        \\      {
        \\        "ticker": {"type": "literal", "value": "AAPL"},
        \\        "security": {"type": "uri", "value": "http://www.wikidata.org/entity/Q312"},
        \\        "securityLabel": {"type": "literal", "value": "Apple Inc."},
        \\        "industryLabel": {"type": "literal", "value": "consumer electronics"},
        \\        "countryCode": {"type": "literal", "value": "US"},
        \\        "instance": {"type": "uri", "value": "http://www.wikidata.org/entity/Q4830453"}
        \\      }
        \\    ]
        \\  }
        \\}
    ;

    const allocator = std.testing.allocator;
    const expected = [_][]const u8{"AAPL"};
    const recs = try parse(std.testing.io, allocator, fixture, &expected);
    defer {
        for (recs) |*r| {
            var m = r.*;
            m.deinit(allocator);
        }
        allocator.free(recs);
    }

    try std.testing.expectEqual(@as(usize, 1), recs.len);
    try std.testing.expectEqualStrings("AAPL", recs[0].symbol);
    try std.testing.expectEqualStrings("Apple Inc.", recs[0].name.?);
    try std.testing.expectEqualStrings("consumer electronics", recs[0].industry.?);
    try std.testing.expectEqualStrings("consumer electronics", recs[0].sector.?);
    try std.testing.expectEqualStrings("US", recs[0].country.?);
    try std.testing.expect(!recs[0].is_etf);
}

test "parse: ETF fixture sets is_etf=true and asset_class" {
    const fixture =
        \\{
        \\  "head": {"vars": ["ticker", "security", "securityLabel", "instance"]},
        \\  "results": {
        \\    "bindings": [
        \\      {
        \\        "ticker": {"type": "literal", "value": "VTI"},
        \\        "security": {"type": "uri", "value": "http://www.wikidata.org/entity/Q1809462"},
        \\        "securityLabel": {"type": "literal", "value": "Vanguard Total Stock Market ETF"},
        \\        "instance": {"type": "uri", "value": "http://www.wikidata.org/entity/Q40244"}
        \\      }
        \\    ]
        \\  }
        \\}
    ;

    const allocator = std.testing.allocator;
    const expected = [_][]const u8{"VTI"};
    const recs = try parse(std.testing.io, allocator, fixture, &expected);
    defer {
        for (recs) |*r| {
            var m = r.*;
            m.deinit(allocator);
        }
        allocator.free(recs);
    }

    try std.testing.expectEqual(@as(usize, 1), recs.len);
    try std.testing.expect(recs[0].is_etf);
    try std.testing.expectEqualStrings("ETF (uncategorized)", recs[0].asset_class.?);
}

test "parse: bindings for symbols not requested are dropped" {
    const fixture =
        \\{
        \\  "head": {"vars": ["ticker", "security", "securityLabel"]},
        \\  "results": {
        \\    "bindings": [
        \\      {"ticker": {"type": "literal", "value": "WRONG"},
        \\       "security": {"type": "uri", "value": "http://example/Q1"},
        \\       "securityLabel": {"type": "literal", "value": "Wrong Co"}}
        \\    ]
        \\  }
        \\}
    ;

    const allocator = std.testing.allocator;
    const expected = [_][]const u8{"AAPL"};
    const recs = try parse(std.testing.io, allocator, fixture, &expected);
    defer allocator.free(recs);

    try std.testing.expectEqual(@as(usize, 0), recs.len);
}

test "geoFor maps known ISO-3166 codes to bucket" {
    try std.testing.expectEqualStrings(geo.us, geoFor("US"));
    try std.testing.expectEqualStrings(geo.us, geoFor("USA"));
    try std.testing.expectEqualStrings(geo.developed, geoFor("GB"));
    try std.testing.expectEqualStrings(geo.developed, geoFor("DE"));
    try std.testing.expectEqualStrings(geo.developed, geoFor("CA"));
    try std.testing.expectEqualStrings(geo.developed, geoFor("IL"));
    try std.testing.expectEqualStrings(geo.emerging, geoFor("CN"));
    try std.testing.expectEqualStrings(geo.emerging, geoFor("TW"));
    try std.testing.expectEqualStrings(geo.emerging, geoFor("KR"));
}

test "geoFor returns Unknown for null/empty/unmapped" {
    try std.testing.expectEqualStrings(geo.unknown, geoFor(null));
    try std.testing.expectEqualStrings(geo.unknown, geoFor(""));
    try std.testing.expectEqualStrings(geo.unknown, geoFor("ZZ")); // unassigned ISO-2
    try std.testing.expectEqualStrings(geo.unknown, geoFor("XX"));
}