/*
 * Copyright (c) 2020, Ben Wiederhake <BenWiederhake.GitHub@gmx.de>
 * Copyright (c) 2022, David Tuin <davidot@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibTest/TestCase.h>

#include <AK/ByteString.h>
#include <AK/Format.h>
#include <stdlib.h>
#include <string.h>

static constexpr char TEXT_ERROR[] = "\x1b[01;35m";
static constexpr char TEXT_WRONG[] = "\x1b[01;31m";
static constexpr char TEXT_OFBY1[] = "\x1b[01;97m";
static constexpr char TEXT_RESET[] = "\x1b[0m";
static constexpr long long LENIENCY = 8;

struct Testcase {
    char const* test_name;
    int should_consume;
    char const* hex;
    char const* test_string;
};

static Testcase TESTCASES[] = {
    // What I came up with on my own:
    { "BW00", 0, "0000000000000000", ".." },
    { "BW01", 2, "3ff0000000000000", "1..0" },
    { "BW02", 1, "3ff0000000000000", "1" },
    { "BW03", 2, "0000000000000000", ".0" },
    { "BW04", 2, "0000000000000000", "0." },
    { "BW05", 2, "0000000000000000", "0.." },
    // Second 'e' overwrites first exponent
    { "BW06", 3, "40af400000000000", "4e3e4" },
    // Minus sign in exponent is ignored (`atof` only)
    { "BW07", 4, "3f747ae147ae147b", "5e-3" },
    // "e" is ignored if followed by only zeros
    { "BW08", 3, "401c000000000000", "7e0" },
    // Exponent overflow:
    { "BW09", -1, "0000000000000000", "1e-4294967296" },
    // Excessive time use(!):
    { "BW10", -1, "0000000000000000", "1e-999999999" },
    // Excessively large exponent (>64 bits):
    { "BW10", -1, "0000000000000000", "1e-9999999999999999999999" },

    // Bugs I nearly introduced
    { "BWN01", 2, "3ff0000000000000", "1.-2" },
    { "BWN02", 2, "3ff0000000000000", "1. 2" },
    { "BWN03", 0, "0000000000000000", "++2" },
    { "BWN04", 1, "0000000000000000", "0b101" },
    { "BWN05", 3, "0000000000000000", "  0b101" },
    { "BWN06", 1, "0000000000000000", "0o123" },
    { "BWN07", 1, "0000000000000000", "0y2" },
    { "BWN08", 1, "3ff0000000000000", "1e" },
    { "BWN09", 1, "3ff0000000000000", "1e-" },
    { "BWN10", 6, "4034000000000000", "2e0001" },
    { "BWN11", 6, "41ddcd6500000000", "2e0009" },
    { "BWN12", 1, "0000000000000000", "0d1" },
    { "BWN13", -1, "7ff0000000000000", "184467440737095516151234567890e2147483639" },
    { "BWN14", -1, "0000000000000000", ".1234567890e-2147483639" },
    { "BWN15", -1, "8000000000000000", "-1e-9999" },
    { "BWN16", -1, "c3389e56ee5e7a58", "-6929495644600919.5" },
    { "BWN17", -1, "c3389e56ee5e7a57", "-6929495644600919" },
    { "BWN18", -1, "630a2b939cbca17f", "12345678901234567890e150" },
    { "BWN19", -1, "24c186a8a3f159df", "12345678901234567890e-150" },

    // From the Serenity GitHub tracker:
    // https://github.com/SerenityOS/serenity/issues/1979
    { "SR1", -1, "4014000000000001", "5.000000000000001" },
    { "SR2", -1, "4014000000000000", "5.0000000000000001" },
    { "SR3", -1, "3ff0000000000000", "1.0000000000000000000000000000001" },
    { "SR4", -1, "3ff0000000000000", "1.00000000000000000000000000000001" },
    { "SR5", -1, "3ff1f9add37c1216", "1.12345678912345678912345678912345" },
    { "SR6", -1, "3ff1f9add37c1216", "1.123456789123456789123456789123456789123456789" },

    // Inspired from Abraham Hrvoje's "negativeFormattingTests":
    // https://github.com/ahrvoje/numerics/blob/master/strtod/strtod_tests.toml
    // Note that my interpretation is slightly stricter than what Abraham Hrvoje wrote.
    { "AHN01", 3, "7ff0000000000000", "inf1" },
    { "AHN02", 3, "7ff0000000000000", "inf+" },
    { "AHN03", 0, "0000000000000000", ".E" },
    { "AHN04", 3, "3ff0000000000000", "1.0e" },
    { "AHN05", 4, "400399999999999a", "2.45+e+3" },
    { "AHN06", 2, "4037000000000000", "23e.23" },
    { "AHN07", 0, "0000000000000000", "e9" },
    { "AHN08", 0, "0000000000000000", "+e" },
    { "AHN09", 0, "0000000000000000", "e+" },
    { "AHN10", 0, "0000000000000000", "." },
    { "AHN11", 0, "0000000000000000", "e" },
    { "AHN12", 2, "3fe6666666666666", ".7+" },
    { "AHN13", 3, "3fcae147ae147ae1", ".21e" },
    { "AHN14", 0, "0000000000000000", "+" },
    { "AHN15", 0, "0000000000000000", "" },
    { "AHN16", 3, "7ff0000000000000", "infe" },
    { "AHN17", 3, "7ff8000000000000", "nan(err" },
    { "AHN18", 3, "7ff8000000000000", "nan)" },
    { "AHN19", 3, "7ff8000000000000", "NAN(test_)_)" },
    { "AHN20", 3, "7ff8000000000000", "nan0" },
    { "AHN21", 0, "0000000000000000", "-.e+" },
    { "AHN22", 0, "0000000000000000", "-+12.34" },

    // For a better description, see:
    // https://github.com/ahrvoje/numerics/blob/master/strtod/strtod_tests.toml
    // (Comments removed for ease of format conversion.)
    // My machine generates the NaN "fff8000000000000" for 0/0, so I replaced the "correct" result by that.
    { "F0", -1, "348834c13cbf331d", "12.34E-56" },
    { "F1", -1, "c07c800000000000", "-456." },
    { "F2", -1, "405ec00000000000", "+123" },
    { "F3", -1, "7ff8000000000000", "nan" },
    { "F4", -1, "7ff8000000000000", "NaN" },
    { "F5", -1, "7ff8000000000000", "NAN" },
    { "F6", -1, "7ff0000000000000", "inf" },
    { "F7", -1, "7ff0000000000000", "Inf" },
    { "F8", -1, "7ff0000000000000", "INF" },
    { "F9", -1, "fff0000000000000", "-inf" },
    { "F10", -1, "7ff0000000000000", "+inF" },
    { "F11", -1, "7ff0000000000000", "+INF" },
    { "F12", -1, "3ff0000000000000", "1.0" },
    { "F13", -1, "4059000000000000", "1e2" },
    { "F14", -1, "44ada56a4b0835c0", "7.e22" },
    { "F15", -1, "44ada56a4b0835c0", "7.0e22" },
    { "F16", -1, "44ada56a4b0835c0", "7.0e+22" },
    { "F17", -1, "3b8a71fc0e147309", "7.0e-22" },
    { "F18", -1, "c02699999999999a", "-1.13e1" },
    { "F19", -1, "402699999999999a", "+1.13e+1" },
    { "F20", -1, "36e069d1347fd4b5", "23e-45" },
    { "F21", -1, "402a000000000000", ".13e2" },
    { "F22", -1, "beb5cf751db94e6b", "-.13e-5" },
    { "F23", -1, "405ec00000000000", "123" },
    { "F24", -1, "7ff8000000000000", "+nan" },
    { "F25", -1, "7ff0000000000000", "infinity" },
    { "F26", -1, "7ff0000000000000", "Infinity" },
    { "F27", 3, "7ff8000000000000", "nan(type-0)" },
    { "F28", 4, "7ff8000000000000", "+nan(catch_22)" },
    { "F29", -1, "7ff0000000000000", "INFINITY" },
    { "F30", -1, "3ff0000000000000", "0.00000001e+8" },
    { "F31", -1, "fff0000000000000", "-infinity" },
    { "F32", -1, "3705f1a59c73408e", "123.e-45" },
    { "F33", -1, "4085300000000000", "678." },
    { "F34", 4, "fff8000000000000", "-nan()" },
    { "C0", -1, "0000000000000000", "0.000e+00" },
    { "C1", -1, "0000000000000000", "1e-400" },
    { "C2", -1, "0000000000000000", "2.4703282292062326e-324" },
    { "C3", -1, "0000000000000000", "2.4703282292062327e-324" },
    { "C4", -1, "0000000000000001", "2.4703282292062328e-324" },
    { "C5", -1, "0000000000000001", "4.9406564584124654e-324" },
    { "C6", -1, "00000000000007e8", "1e-320" },
    { "C7", -1, "000fffffffffffff", "2.2250738585072009e-308" },
    { "C8", -1, "0010000000000000", "2.2250738585072014e-308" },
    { "C9", -1, "3abef2d0f5da7dd9", "1e-25" },
    { "C10", -1, "3b282db34012b251", "1.0e-23" },
    { "C11", -1, "3ff3c0ca428c59fb", "1.2345678901234567890" },
    { "C12", -1, "402699999999999a", "1.13e1" },
    { "C13", -1, "43e158e460913d00", "1e+19" },
    { "C14", -1, "449017f7df96be18", "1.9e+22" },
    { "C15", -1, "4496deb1154f79ec", "2.7e22" },
    { "C16", -1, "449a420db02bd7d6", "3.1e22" },
    { "C17", -1, "44ada56a4b0835c0", "7e22" },
    { "C18", -1, "7fefffffffffffff", "1.7976931348623158e+308" },
    { "C19", -1, "7ff0000000000000", "1.7976931348623159e+308" },
    { "C20", -1, "7ff0000000000000", "1e+400" },
    { "C21", -1, "000fffffffffffff", "2.225073858507201136057409796709131975934819546351645648023426109724822222021076945516529523908135087914149158913039621106870086438694594645527657207407820621743379988141063267329253552286881372149012981122451451889849057222307285255133155755015914397476397983411801999323962548289017107081850690630666655994938275772572015763062690663332647565300009245888316433037779791869612049497390377829704905051080609940730262937128958950003583799967207254304360284078895771796150945516748243471030702609144621572289880258182545180325707018860872113128079512233426288368622321503775666622503982534335974568884423900265498198385487948292206894721689831099698365846814022854243330660339850886445804001034933970427567186443383770486037861622771738545623065874679014086723327636718749999999999999999999999999999999999999e-308" },
    { "C22", -1, "0010000000000000", "2.22507385850720113605740979670913197593481954635164564802342610972482222202107694551652952390813508791414915891303962110687008643869459464552765720740782062174337998814106326732925355228688137214901298112245145188984905722230728525513315575501591439747639798341180199932396254828901710708185069063066665599493827577257201576306269066333264756530000924588831643303777979186961204949739037782970490505108060994073026293712895895000358379996720725430436028407889577179615094551674824347103070260914462157228988025818254518032570701886087211312807951223342628836862232150377566662250398253433597456888442390026549819838548794829220689472168983109969836584681402285424333066033985088644580400103493397042756718644338377048603786162277173854562306587467901408672332763671875e-308" },
    { "C23", -1, "0010000000000000", "0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000222507385850720138309023271733240406421921598046233183055332741688720443481391819585428315901251102056406733973103581100515243416155346010885601238537771882113077799353200233047961014744258363607192156504694250373420837525080665061665815894872049117996859163964850063590877011830487479978088775374994945158045160505091539985658247081864511353793580499211598108576605199243335211435239014879569960959128889160299264151106346631339366347758651302937176204732563178148566435087212282863764204484681140761391147706280168985324411002416144742161856716615054015428508471675290190316132277889672970737312333408698898317506783884692609277397797285865965494109136909540613646756870239867831529068098461721092462539672851562500000000000000001" },
    { "C24", -1, "7ff0000000000000", "179769313486231580793728971405303415079934132710037826936173778980444968292764750946649017977587207096330286416692887910946555547851940402630657488671505820681908902000708383676273854845817711531764475730270069855571366959622842914819860834936475292719074168444365510704342711559699508093042880177904174497792" },
    { "C25", -1, "7fefffffffffffff", "179769313486231580793728971405303415079934132710037826936173778980444968292764750946649017977587207096330286416692887910946555547851940402630657488671505820681908902000708383676273854845817711531764475730270069855571366959622842914819860834936475292719074168444365510704342711559699508093042880177904174497791.9999999999999999999999999999999999999999999999999999999999999999999999" },
    { "C26", -1, "0010000000000000", "2.2250738585072012e-308" },
    { "C27", -1, "0006123400000001", "8.44291197326099e-309" },
    { "C28", -1, "42c0000000000000", "35184372088831.999999999999999999999999999999999999" },
    { "C29", -1, "0000000000000000", "2.47032822920623272e-324" },
    { "C30", -1, "3ff199999999999a", "1.100000000000000088817841970012523233890533447265626" },
    { "C31", -1, "3f847ae147ae147b", ".010000000000000000057612911342378542997169" },
    { "C32", -1, "3ffd34fd8378ea83", "1.8254370818746402660437411213933955878019332885742187" },
    { "C33", -1, "43389e56ee5e7a58", "6929495644600919.5" },
    { "C34", -1, "432a9d28ff412a75", "3.7455744005952583e15" },
    { "C35", -1, "000fffffffffffff", "2.2250738585072011e-308" },
    { "C36", -1, "4c20000000000001", "5.0216813883093451685872615018317116712748411717802652598273e58" },
    { "C37", -1, "0000000008000000", "6.631236871469758276785396630275967243399099947355303144249971758736286630139265439618068200788048744105960420552601852889715006376325666595539603330361800519107591783233358492337208057849499360899425128640718856616503093444922854759159988160304439909868291973931426625698663157749836252274523485312442358651207051292453083278116143932569727918709786004497872322193856150225415211997283078496319412124640111777216148110752815101775295719811974338451936095907419622417538473679495148632480391435931767981122396703443803335529756003353209830071832230689201383015598792184172909927924176339315507402234836120730914783168400715462440053817592702766213559042115986763819482654128770595766806872783349146967171293949598850675682115696218943412532098591327667236328125E-316" },
    { "C38", -1, "0000000000010000", "3.237883913302901289588352412501532174863037669423108059901297049552301970670676565786835742587799557860615776559838283435514391084153169252689190564396459577394618038928365305143463955100356696665629202017331344031730044369360205258345803431471660032699580731300954848363975548690010751530018881758184174569652173110473696022749934638425380623369774736560008997404060967498028389191878963968575439222206416981462690113342524002724385941651051293552601421155333430225237291523843322331326138431477823591142408800030775170625915670728657003151953664260769822494937951845801530895238439819708403389937873241463484205608000027270531106827387907791444918534771598750162812548862768493201518991668028251730299953143924168545708663913273994694463908672332763671875E-319" },
    { "C39", -1, "0000800000000100", "6.953355807847677105972805215521891690222119817145950754416205607980030131549636688806115726399441880065386399864028691275539539414652831584795668560082999889551357784961446896042113198284213107935110217162654939802416034676213829409720583759540476786936413816541621287843248433202369209916612249676005573022703244799714622116542188837770376022371172079559125853382801396219552418839469770514904192657627060319372847562301074140442660237844114174497210955449896389180395827191602886654488182452409583981389442783377001505462015745017848754574668342161759496661766020028752888783387074850773192997102997936619876226688096314989645766000479009083731736585750335262099860150896718774401964796827166283225641992040747894382698751809812609536720628966577351093292236328125E-310" },
    { "C40", -1, "0000000000010800", "3.339068557571188581835713701280943911923401916998521771655656997328440314559615318168849149074662609099998113009465566426808170378434065722991659642619467706034884424989741080790766778456332168200464651593995817371782125010668346652995912233993254584461125868481633343674905074271064409763090708017856584019776878812425312008812326260363035474811532236853359905334625575404216060622858633280744301892470300555678734689978476870369853549413277156622170245846166991655321535529623870646888786637528995592800436177901746286272273374471701452991433047257863864601424252024791567368195056077320885329384322332391564645264143400798619665040608077549162173963649264049738362290606875883456826586710961041737908872035803481241600376705491726170293986797332763671875E-319" },
    { "C41", -1, "4e3fa69165a8eea2", "8.533e+68" },
    { "C42", -1, "19dbe0d1c7ea60c9", "4.1006e-184" },
    { "C43", -1, "7fe1cc0a350ca87b", "9.998e+307" },
    { "C44", -1, "0602117ae45cde43", "9.9538452227e-280" },
    { "C45", -1, "0a1fdd9e333badad", "6.47660115e-260" },
    { "C46", -1, "49e033d7eca0adef", "7.4e+47" },
    { "C47", -1, "4a1033d7eca0adef", "5.92e+48" },
    { "C48", -1, "4dd172b70eababa9", "7.35e+66" },
    { "C49", -1, "4b8b2628393e02cd", "8.32116e+55" },
    { "C50", -1, "bfed35696e58a32f", "-0.91276999999999997026378650843980722129344940185546876" },
    { "C51", -1, "c070a3d70a3d70a4", "-266.240000000000009094947017729282379150390624" },
    { "C52", -1, "3c97cb9433617c9c", "8.255628858767918002472043289952338102302250764062685473021474535926245152950286865234374e-17" },
    { "C53", -1, "43405e6cec57761a", "9214843084008499" },
    { "C54", -1, "3fe0000000000002", "0.500000000000000166533453693773481063544750213623046875" },
    { "C55", -1, "42c0000000000002", "3.518437208883201171875e13" },
    { "C56", -1, "404f44abd5aa7ca4", "62.5364939768271845828" },
    { "C57", -1, "3e0bd5cbaef0fd0c", "8.10109172351e-10" },
    { "C58", -1, "3ff8000000000000", "1.50000000000000011102230246251565404236316680908203125" },
    { "C59", -1, "433fffffffffffff", "9007199254740991.4999999999999999999999999999999995" },
    { "C60", -1, "44997a3c7271b021", "30078505129381147446200" },
    { "C61", -1, "4458180d5bad2e3e", "1777820000000000000001" },
    { "C62", -1, "3fe0000000000002", "0.50000000000000016656055874808561867439493653364479541778564453125" },
    { "C63", -1, "3fd92bb352c4623a", "0.3932922657273" },
    { "C64", -1, "0000000000000000", "2.4703282292062327208828439643411068618252990130716238221279284125033775363510437593264991818081799618989828234772285886546332835517796989819938739800539093906315035659515570226392290858392449105184435931802849936536152500319370457678249219365623669863658480757001585769269903706311928279558551332927834338409351978015531246597263579574622766465272827220056374006485499977096599470454020828166226237857393450736339007967761930577506740176324673600968951340535537458516661134223766678604162159680461914467291840300530057530849048765391711386591646239524912623653881879636239373280423891018672348497668235089863388587925628302755995657524455507255189313690836254779186948667994968324049705821028513185451396213837722826145437693412532098591327667236328124999e-324" },
    { "C65", -1, "0000000000000000", "2.4703282292062327208828439643411068618252990130716238221279284125033775363510437593264991818081799618989828234772285886546332835517796989819938739800539093906315035659515570226392290858392449105184435931802849936536152500319370457678249219365623669863658480757001585769269903706311928279558551332927834338409351978015531246597263579574622766465272827220056374006485499977096599470454020828166226237857393450736339007967761930577506740176324673600968951340535537458516661134223766678604162159680461914467291840300530057530849048765391711386591646239524912623653881879636239373280423891018672348497668235089863388587925628302755995657524455507255189313690836254779186948667994968324049705821028513185451396213837722826145437693412532098591327667236328125e-324" },
    { "C66", -1, "0000000000000001", "2.4703282292062327208828439643411068618252990130716238221279284125033775363510437593264991818081799618989828234772285886546332835517796989819938739800539093906315035659515570226392290858392449105184435931802849936536152500319370457678249219365623669863658480757001585769269903706311928279558551332927834338409351978015531246597263579574622766465272827220056374006485499977096599470454020828166226237857393450736339007967761930577506740176324673600968951340535537458516661134223766678604162159680461914467291840300530057530849048765391711386591646239524912623653881879636239373280423891018672348497668235089863388587925628302755995657524455507255189313690836254779186948667994968324049705821028513185451396213837722826145437693412532098591327667236328125001e-324" },
    { "C67", -1, "0000000000000001", "7.4109846876186981626485318930233205854758970392148714663837852375101326090531312779794975454245398856969484704316857659638998506553390969459816219401617281718945106978546710679176872575177347315553307795408549809608457500958111373034747658096871009590975442271004757307809711118935784838675653998783503015228055934046593739791790738723868299395818481660169122019456499931289798411362062484498678713572180352209017023903285791732520220528974020802906854021606612375549983402671300035812486479041385743401875520901590172592547146296175134159774938718574737870961645638908718119841271673056017045493004705269590165763776884908267986972573366521765567941072508764337560846003984904972149117463085539556354188641513168478436313080237596295773983001708984374999e-324" },
    { "C68", -1, "0000000000000002", "7.4109846876186981626485318930233205854758970392148714663837852375101326090531312779794975454245398856969484704316857659638998506553390969459816219401617281718945106978546710679176872575177347315553307795408549809608457500958111373034747658096871009590975442271004757307809711118935784838675653998783503015228055934046593739791790738723868299395818481660169122019456499931289798411362062484498678713572180352209017023903285791732520220528974020802906854021606612375549983402671300035812486479041385743401875520901590172592547146296175134159774938718574737870961645638908718119841271673056017045493004705269590165763776884908267986972573366521765567941072508764337560846003984904972149117463085539556354188641513168478436313080237596295773983001708984375e-324" },
    { "C69", -1, "0000000000000002", "7.4109846876186981626485318930233205854758970392148714663837852375101326090531312779794975454245398856969484704316857659638998506553390969459816219401617281718945106978546710679176872575177347315553307795408549809608457500958111373034747658096871009590975442271004757307809711118935784838675653998783503015228055934046593739791790738723868299395818481660169122019456499931289798411362062484498678713572180352209017023903285791732520220528974020802906854021606612375549983402671300035812486479041385743401875520901590172592547146296175134159774938718574737870961645638908718119841271673056017045493004705269590165763776884908267986972573366521765567941072508764337560846003984904972149117463085539556354188641513168478436313080237596295773983001708984375001e-324" },
    { "C70", -1, "7fe0000000000000", "8.9884656743115805365666807213050294962762414131308158973971342756154045415486693752413698006024096935349884403114202125541629105369684531108613657287705365884742938136589844238179474556051429647415148697857438797685859063890851407391008830874765563025951597582513936655578157348020066364210154316532161708031999e+307" },
    { "C71", -1, "7fe0000000000000", "8.9884656743115805365666807213050294962762414131308158973971342756154045415486693752413698006024096935349884403114202125541629105369684531108613657287705365884742938136589844238179474556051429647415148697857438797685859063890851407391008830874765563025951597582513936655578157348020066364210154316532161708032e+307" },
    { "C72", -1, "7fe0000000000001", "8.9884656743115805365666807213050294962762414131308158973971342756154045415486693752413698006024096935349884403114202125541629105369684531108613657287705365884742938136589844238179474556051429648741514697857438797685859063890851407391008830874765563025951597582513936655578157348020066364210154316532161708032001e+307" },
    { "C73", -1, "3ff0000010000000", "1.00000005960464477550" },
    { "C74", -1, "36c6000000000000", "7.7071415537864938e-45" },
    { "C75", -1, "0000000000000000", "2183167012312112312312.23538020374420446192e-370" },
    { "C76", -1, "0006c9a143590c14", "94393431193180696942841837085033647913224148539854e-358" },
    { "C77", -1, "3ff0000000000000", "99999999999999994487665465554760717039532578546e-47" },
    { "C78", -1, "44b52d02c7e14af6", "10000000000000000000000000000000000000000e-17" },
    { "C79", -1, "0007802665fd9600", "104308485241983990666713401708072175773165034278685682646111762292409330928739751702404658197872319129036519947435319418387839758990478549477777586673075945844895981012024387992135617064532141489278815239849108105951619997829153633535314849999674266169258928940692239684771590065027025835804863585454872499320500023126142553932654370362024104462255244034053203998964360882487378334860197725139151265590832887433736189468858614521708567646743455601905935595381852723723645799866672558576993978025033590728687206296379801363024094048327273913079612469982585674824156000783167963081616214710691759864332339239688734656548790656486646106983450809073750535624894296242072010195710276073042036425579852459556183541199012652571123898996574563824424330960027873516082763671875e-1075" },
    { "C80", -1, "4025cccccccccccd", "10.900000000000000012345678912345678912345" },

    // Hexadecimal floats.
    // Hex floats do not allow hexadecimal digits in the exponent
    { "Fp1.1", 7, "406579a000000000", "0xab.cdpef" },
    { "Fp1.1", 7, "406579a000000000", "0xab.cdp-ef" },
    { "Fp1.1", 7, "406579a000000000", "0xab.cdpe-f" },
    { "Fp1.1", 7, "406579a000000000", "0xab.cdpef-" },
    { "Fp1.2", 11, "7c9579a000000000", "0xab.cdp963" },
    { "Fp1.3", 12, "7c9579a000000000", "0xab.cdp+963" },
    { "Fp1.4", 12, "7c2579a000000000", "0xab.cdp+956" },
    { "Fp1.4", 12, "7c1579a000000000", "0xab.cdp+955" },
    { "Fp1.5", 12, "04a579a000000000", "0xab.cdp-956" },
    // Sneaky floating point :P
    { "Fp2.1", 4, "4069400000000000", "0xCAPE" },
    { "Fp2.1", 4, "4069400000000000", "0xCAP-E" },
    { "Fp2.2", 6, "4069400000000000", "0xCAP0" },
    { "Fp2.2", 7, "4069400000000000", "0xCAP+0" },
    { "Fp2.2", 7, "4069400000000000", "0xCAP-0" },
    { "Fp2.3", 7, "4159400000000000", "0xCAP15" },
    { "Fp2.4", 7, "4459400000000000", "0xCAP63" },
    { "Fp2.5", 7, "43e9400000000000", "0xCAP56" },
};

constexpr size_t NUM_TESTCASES = sizeof(TESTCASES) / sizeof(TESTCASES[0]);

typedef double (*strtod_fn_t)(char const* str, char** endptr);

static long long cast_ll(double d)
{
    union readable_t {
        double as_double;
        long long as_ll;
    };
    typedef char assert_double_8bytes[sizeof(double) == 8 ? 1 : -1];
    [[maybe_unused]] auto double_size = sizeof(assert_double_8bytes);
    typedef char assert_ll_8bytes[sizeof(long long) == 8 ? 1 : -1];
    [[maybe_unused]] auto longlong_size = sizeof(assert_ll_8bytes);
    typedef char assert_readable_8bytes[sizeof(readable_t) == 8 ? 1 : -1];
    [[maybe_unused]] auto readable8_size = sizeof(assert_readable_8bytes);
    readable_t readable;
    readable.as_double = d;
    return readable.as_ll;
}

static bool is_strtod_close(strtod_fn_t strtod_fn, char const* test_string, char const* expect_hex, int expect_consume, long long expect_ll)
{
    union readable_t {
        double as_double;
        unsigned char as_bytes[8];
    };
    typedef char assert_double_8bytes[sizeof(double) == 8 ? 1 : -1];
    [[maybe_unused]] auto double_size = sizeof(assert_double_8bytes);
    typedef char assert_readable_8bytes[sizeof(readable_t) == 8 ? 1 : -1];
    [[maybe_unused]] auto readable8_size = sizeof(assert_readable_8bytes);
    readable_t readable;
    char* endptr = (char*)0x123;

    readable.as_double = strtod_fn(test_string, &endptr);

    char actual_hex[16 + 1] = { 0 };
    for (size_t i = 0; i < 8; ++i) {
        // Little endian, need to reverse order.
        snprintf(&actual_hex[2 * i], 3, "%02x", readable.as_bytes[8 - 1 - i]);
    }

    bool actual_consume_possible = false;
    int actual_consume;

    if (endptr < test_string) {
        actual_consume = 999;
    } else {
        char const* max_endptr = test_string + strlen(test_string);
        actual_consume_possible = endptr <= max_endptr;
        actual_consume = endptr - test_string;
    }

    long long actual_ll = cast_ll(readable.as_double);
    long long off_by = expect_ll - actual_ll;

    bool ofby1_hex = off_by != 0 && -LENIENCY <= off_by && off_by <= LENIENCY;
    bool wrong_hex = !ofby1_hex && strcmp(expect_hex, actual_hex) != 0;
    bool error_cns = !actual_consume_possible;
    bool wrong_cns = !error_cns && (actual_consume != expect_consume);

    out(" {}{}{}({}{:2}{})",
        ofby1_hex ? TEXT_OFBY1 : wrong_hex ? TEXT_WRONG
                                           : "",
        actual_hex,
        (ofby1_hex || wrong_hex) ? TEXT_RESET : "",
        error_cns ? TEXT_ERROR : wrong_cns ? TEXT_WRONG
                                           : "",
        actual_consume,
        (error_cns || wrong_cns) ? TEXT_RESET : "");

    return !(wrong_hex || error_cns || wrong_cns);
}

static long long hex_to_ll(char const* hex)
{
    long long result = 0;
    for (int i = 0; i < 16; ++i) {
        char ch = *(hex + i);
        int digit;
        if ('0' <= ch && ch <= '9') {
            digit = ch - '0';
        } else if ('a' <= ch && ch <= 'f') {
            digit = ch - 'a' + 10;
        } else {
            FAIL(ByteString::formatted("\n!!! Encountered char {:02x} at {}", ch, i));
            return result;
        }
        result <<= 4;
        result += digit;
    }
    return result;
}

TEST_CASE(strtod_accuracy)
{
    outln("Running {} testcases...", NUM_TESTCASES);
    outln("{:3}({:-5}): {:16}({:2}) {:16}({:2}) - {}", "num", "name", "correct", "cs", "strtod", "cs", "teststring");

    int successes = 0;
    int fails = 0;
    for (size_t i = 0; i < NUM_TESTCASES; i++) {
        Testcase& tc = TESTCASES[i];
        if (tc.should_consume == -1) {
            tc.should_consume = strlen(tc.test_string);
        }
        out("{:3}({:-5}): {}({:2})", i, tc.test_name, tc.hex, tc.should_consume);
        long long expect_ll = hex_to_ll(tc.hex);

        bool success = false;
        success = is_strtod_close(strtod, tc.test_string, tc.hex, tc.should_consume, expect_ll);
        outln(" from {}", tc.test_string);

        if (success) {
            successes += 1;
        } else {
            fails += 1;
        }
    }
    outln("Out of {} tests, saw {} successes and {} fails.", NUM_TESTCASES, successes, fails);
    if (fails != 0) {
        FAIL(ByteString::formatted("{} strtod tests failed", fails));
    }

    outln("PASS (with leniency up to {} ULP from the exact solution)", LENIENCY);
}

TEST_CASE(test_strtod_sets_errno)
{
#define EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO_BASE(str_value, double_value)                    \
    do {                                                                                   \
        errno = 0;                                                                         \
        auto value = strtod(str_value, nullptr);                                           \
        EXPECT_EQ(errno, 0);                                                               \
        EXPECT_EQ(bit_cast<u64>(value), bit_cast<u64>(static_cast<double>(double_value))); \
    } while (false)

#define EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO(str_value, double_value)        \
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO_BASE(str_value, double_value);      \
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO_BASE("  " str_value, double_value); \
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO_BASE("\t" str_value, double_value); \
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO_BASE("\n" str_value, double_value)

    // Leading zeros are allowed
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("0", 0.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("00", 0.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("000", 0.);

    // FIXME: Verify we only parse up to the appropriate point
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("0xT", 0.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("0xp20", 0.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("0x.t", 0.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("0x.pt", 0.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("0x1.p0", 1.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("0x1.pa", 1.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("0x.1pa", 0x0.1p0);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("0x.fpa", 0x0.fp0);

    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-0xT", -0.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-0xp20", -0.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-0x.t", -0.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-0x.pt", -0.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-0x1.p0", -1.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-0x1.pa", -1.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-0x.1pa", -0x0.1p0);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-0x.fpa", -0x0.fp0);

    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("1", 1.);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("10e10", 10e10);
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("10.10e10", 10.10e10);

    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("inf", __builtin_huge_val());
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("infinity", __builtin_huge_val());
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("INF", __builtin_huge_val());
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("INFINITY", __builtin_huge_val());

    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("Inf", __builtin_huge_val());
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("iNf", __builtin_huge_val());
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("inF", __builtin_huge_val());

    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-inf", -__builtin_huge_val());
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-infinity", -__builtin_huge_val());
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-INF", -__builtin_huge_val());
    EXPECT_TO_GIVE_VALUE_WITH_0_ERRNO("-INFINITY", -__builtin_huge_val());

#define EXPECT_TO_GIVE_VALUE_WITH_ERRNO(str_value, double_value, errno_value)              \
    do {                                                                                   \
        errno = 0;                                                                         \
        auto value = strtod(str_value, nullptr);                                           \
        EXPECT_EQ(errno, errno_value);                                                     \
        EXPECT_EQ(bit_cast<u64>(value), bit_cast<u64>(static_cast<double>(double_value))); \
    } while (false)

    EXPECT_TO_GIVE_VALUE_WITH_ERRNO("nan", __builtin_nan(""), ERANGE);
    EXPECT_TO_GIVE_VALUE_WITH_ERRNO("10e10000", __builtin_huge_val(), ERANGE);
    EXPECT_TO_GIVE_VALUE_WITH_ERRNO("0x1p10000", __builtin_huge_val(), ERANGE);
    EXPECT_TO_GIVE_VALUE_WITH_ERRNO("-10e10000", -__builtin_huge_val(), ERANGE);
    EXPECT_TO_GIVE_VALUE_WITH_ERRNO("-0x1p10000", -__builtin_huge_val(), ERANGE);
    EXPECT_TO_GIVE_VALUE_WITH_ERRNO("10e-10000", 0, ERANGE);
    EXPECT_TO_GIVE_VALUE_WITH_ERRNO("0x1p-10000", 0, ERANGE);
    EXPECT_TO_GIVE_VALUE_WITH_ERRNO("-0x1p-10000", -0., ERANGE);
}