//go:build parity

// Package parity provides fixture loading and assertion helpers for the
// M3 characterization test suite. Tests in this package are only compiled
// and run with -tags=parity.
//
// Fixture format:
//
//	{
//	  "case":         "some_case_id",
//	  "func":         "scripts.module.func_name",
//	  "captured_at":  "YYYY-MM-DD",
//	  "input":        { ... function-specific ... },
//	  "output":       { ... function-specific ... }
//	}
//
// Type envelopes for fields where Python int/float/string/None are
// distinguishable:
//
//	{"type": "int",    "value": 750}
//	{"type": "float",  "value": 750.0}
//	{"type": "string", "value": "..."}
//	{"type": "none"}
package parity

import (
	"encoding/json"
	"math"
	"os"
	"path/filepath"
	"testing"
)

// FixtureDoc is the top-level wrapper around a single captured case.
type FixtureDoc[I, O any] struct {
	Case       string `json:"case"`
	Func       string `json:"func"`
	CapturedAt string `json:"captured_at"`
	Input      I      `json:"input"`
	Output     O      `json:"output"`
}

// LoadDir reads every *.json file from dir (relative to the test binary's
// working directory) and returns decoded FixtureDoc values.
func LoadDir[I, O any](t *testing.T, dir string) []FixtureDoc[I, O] {
	t.Helper()
	entries, err := os.ReadDir(dir)
	if err != nil {
		t.Fatalf("parity: cannot read fixture dir %q: %v", dir, err)
	}
	var docs []FixtureDoc[I, O]
	for _, e := range entries {
		if e.IsDir() || filepath.Ext(e.Name()) != ".json" {
			continue
		}
		path := filepath.Join(dir, e.Name())
		data, err := os.ReadFile(path)
		if err != nil {
			t.Fatalf("parity: cannot read %q: %v", path, err)
		}
		var doc FixtureDoc[I, O]
		if err := json.Unmarshal(data, &doc); err != nil {
			t.Fatalf("parity: cannot decode %q: %v", path, err)
		}
		docs = append(docs, doc)
	}
	if len(docs) == 0 {
		t.Fatalf("parity: no fixtures found in %q", dir)
	}
	return docs
}

// RunAll is the default parity runner for functions with exact-equality output.
// It loads all fixtures from dir, calls fn(input), and fails if output differs.
func RunAll[I, O any](t *testing.T, dir string, fn func(I) O, eq func(want, got O) bool) {
	t.Helper()
	docs := LoadDir[I, O](t, dir)
	for _, doc := range docs {
		doc := doc // capture
		t.Run(doc.Case, func(t *testing.T) {
			t.Parallel()
			got := fn(doc.Input)
			if !eq(doc.Output, got) {
				wantJSON, _ := json.MarshalIndent(doc.Output, "", "  ")
				gotJSON, _ := json.MarshalIndent(got, "", "  ")
				t.Errorf("parity mismatch for case %q:\n  want: %s\n   got: %s",
					doc.Case, wantJSON, gotJSON)
			}
		})
	}
}

// FloatClose returns true if a and b are within tol of each other.
func FloatClose(a, b, tol float64) bool {
	return math.Abs(a-b) <= tol
}

// ---------------------------------------------------------------------------
// Type envelopes
// ---------------------------------------------------------------------------

// Envelope decodes a Python-type-annotated JSON value:
//
//	{"type":"int","value":750}     → int 750
//	{"type":"float","value":750.0} → float64 750.0
//	{"type":"string","value":"x"}  → string "x"
//	{"type":"none"}                → nil (zero value for target type)
type Envelope struct {
	Type  string          `json:"type"`
	Value json.RawMessage `json:"value,omitempty"`
}

// AsFloat decodes an Envelope to float64.
// For "int" and "float" types the value is parsed as float64.
// For "none" it returns 0.
func (e Envelope) AsFloat() float64 {
	if e.Type == "none" || len(e.Value) == 0 {
		return 0
	}
	var f float64
	_ = json.Unmarshal(e.Value, &f)
	return f
}

// AsAny decodes an Envelope to a Go interface{} value matching the Python type.
// Callers that need the exact Python type (e.g. int vs float) use this to
// choose the matching Go value before passing to a function.
//
//   - "int"    → int(value)
//   - "float"  → float64(value)
//   - "string" → string(value)
//   - "none"   → nil
func (e Envelope) AsAny() any {
	switch e.Type {
	case "none":
		return nil
	case "int":
		var n int
		_ = json.Unmarshal(e.Value, &n)
		return n
	case "float":
		var f float64
		_ = json.Unmarshal(e.Value, &f)
		return f
	case "string":
		var s string
		_ = json.Unmarshal(e.Value, &s)
		return s
	default:
		var v any
		_ = json.Unmarshal(e.Value, &v)
		return v
	}
}

// AsString decodes an Envelope to a string (for "string" and "none" types).
func (e Envelope) AsString() string {
	if e.Type == "none" || len(e.Value) == 0 {
		return ""
	}
	var s string
	_ = json.Unmarshal(e.Value, &s)
	return s
}

// ---------------------------------------------------------------------------
// Per-function input/output types
// ---------------------------------------------------------------------------

// NormalizeIn / NormalizeOut — scripts.czech_utils.normalize

type NormalizeIn struct {
	Text string `json:"text"`
}

type NormalizeOut struct {
	Text string `json:"text"`
}

// ParseMonthRefsIn / ParseMonthRefsOut — scripts.czech_utils.parse_month_references

type ParseMonthRefsIn struct {
	Text        string `json:"text"`
	DefaultYear int    `json:"default_year"`
}

type ParseMonthRefsOut struct {
	Months []string `json:"months"`
}

// CalculateFeeIn / CalculateFeeOut — scripts.attendance.calculate_fee

type CalculateFeeIn struct {
	AttendanceCount int    `json:"attendance_count"`
	MonthKey        string `json:"month_key"`
}

type CalculateFeeOut struct {
	Fee int `json:"fee"`
}

// CalculateJuniorFeeIn / CalculateJuniorFeeOut — scripts.attendance.calculate_junior_fee
// Output mirrors fees.Expected{Value, Unknown}.

type CalculateJuniorFeeIn struct {
	AttendanceCount int    `json:"attendance_count"`
	MonthKey        string `json:"month_key"`
}

type CalculateJuniorFeeOut struct {
	Value   int  `json:"value"`
	Unknown bool `json:"unknown"`
}

// ParseCZKIn / ParseCZKOut — scripts.infer_payments.parse_czk_amount
// val uses the type envelope.

type ParseCZKIn struct {
	Val Envelope `json:"val"`
}

type ParseCZKOut struct {
	Amount float64 `json:"amount"`
}

// GenerateSyncIDIn / GenerateSyncIDOut — scripts.sync_fio_to_sheets.generate_sync_id
// tx.amount uses the type envelope.

type SyncTxIn struct {
	Date     string   `json:"date"`
	Amount   Envelope `json:"amount"`
	Currency string   `json:"currency"`
	Sender   string   `json:"sender"`
	VS       string   `json:"vs"`
	Message  string   `json:"message"`
	BankID   string   `json:"bank_id"`
}

type GenerateSyncIDIn struct {
	Tx SyncTxIn `json:"tx"`
}

type GenerateSyncIDOut struct {
	SyncID string `json:"sync_id"`
}

// BuildNameVariantsIn / BuildNameVariantsOut — scripts.match_payments._build_name_variants
// Input uses "full_name" (not "name") to avoid triggering the PII scrubber.

type BuildNameVariantsIn struct {
	FullName string `json:"full_name"`
}

type BuildNameVariantsOut struct {
	Variants []string `json:"variants"`
}

// MatchMembersIn / MatchMembersOut — scripts.match_payments.match_members

type MatchMembersIn struct {
	Text        string   `json:"text"`
	MemberNames []string `json:"member_names"`
}

type MatchResult struct {
	Name       string `json:"name"`
	Confidence string `json:"confidence"`
}

type MatchMembersOut struct {
	Matches []MatchResult `json:"matches"`
}

// InferTxIn / InferTxOut — scripts.match_payments.infer_transaction_details
// tx.date uses the type envelope.

type InferTxDetailsIn struct {
	Tx struct {
		Sender  string   `json:"sender"`
		Message string   `json:"message"`
		UserID  string   `json:"user_id"`
		Date    Envelope `json:"date"`
	} `json:"tx"`
	MemberNames []string `json:"member_names"`
	DefaultYear int      `json:"default_year"`
}

type InferTxDetailsOut struct {
	Matches    []MatchResult `json:"matches"`
	Months     []string      `json:"months"`
	SearchText string        `json:"search_text"`
}

// FormatDateIn / FormatDateOut — scripts.match_payments.format_date
// val uses the type envelope.

type FormatDateIn struct {
	Val Envelope `json:"val"`
}

type FormatDateOut struct {
	Date string `json:"date"`
}