// Copyright (C) 2022-2023  Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later

package lowmemjson_test

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"strings"
	"testing"

	"github.com/stretchr/testify/assert"

	"git.lukeshu.com/go/lowmemjson"
)

type ShortSum string

func (s ShortSum) EncodeJSON(w io.Writer) error {
	// Test that it's OK to call lowmemjson.Encoder.Encode for the top-level value in a method.
	return lowmemjson.NewEncoder(w).Encode(string(s))
}

type SumRun struct {
	ChecksumSize int   `json:",omitempty"`
	Addr         int64 `json:",omitempty"`
	Sums         ShortSum
}

func (run SumRun) Size() int64 {
	return int64(len(run.Sums)/(2*run.ChecksumSize)) * (4 * 1024)
}

type SumRunWithGaps struct {
	Addr int64
	Size int64
	Runs []SumRun
}

func (sg SumRunWithGaps) EncodeJSON(w io.Writer) error {
	if _, err := fmt.Fprintf(w, `{"Addr":%d,"Size":%d,"Runs":[`, sg.Addr, sg.Size); err != nil {
		return err
	}
	cur := sg.Addr
	for i, run := range sg.Runs {
		if i > 0 {
			if _, err := w.Write([]byte{','}); err != nil {
				return err
			}
		}
		switch {
		case run.Addr < cur:
			return fmt.Errorf("invalid %T: addr went backwards: %v < %v", sg, run.Addr, cur)
		case run.Addr > cur:
			if _, err := fmt.Fprintf(w, `{"Gap":%d},`, run.Addr-cur); err != nil {
				return err
			}
			fallthrough
		default:
			if err := lowmemjson.NewEncoder(w).Encode(run); err != nil {
				return err
			}
			cur = run.Addr + run.Size()
		}
	}
	end := sg.Addr + sg.Size
	switch {
	case end < cur:
		return fmt.Errorf("invalid %T: addr went backwards: %v < %v", sg, end, cur)
	case end > cur:
		if _, err := fmt.Fprintf(w, `,{"Gap":%d}`, end-cur); err != nil {
			return err
		}
	}
	if _, err := w.Write([]byte("]}")); err != nil {
		return err
	}
	return nil
}

func (sg *SumRunWithGaps) DecodeJSON(r io.RuneScanner) error {
	*sg = SumRunWithGaps{}
	var name string
	return lowmemjson.DecodeObject(r,
		func(r io.RuneScanner) error {
			return lowmemjson.NewDecoder(r).Decode(&name)
		},
		func(r io.RuneScanner) error {
			switch name {
			case "Addr":
				return lowmemjson.NewDecoder(r).Decode(&sg.Addr)
			case "Size":
				return lowmemjson.NewDecoder(r).Decode(&sg.Size)
			case "Runs":
				return lowmemjson.DecodeArray(r, func(r io.RuneScanner) error {
					var run SumRun
					if err := lowmemjson.NewDecoder(r).Decode(&run); err != nil {
						return err
					}
					if run.ChecksumSize > 0 {
						sg.Runs = append(sg.Runs, run)
					}
					return nil
				})
			default:
				return fmt.Errorf("unknown key %q", name)
			}
		})
}

func TestMethods(t *testing.T) {
	t.Parallel()
	in := SumRunWithGaps{
		Addr: 13631488,
		Size: 416033783808,
		Runs: []SumRun{
			{
				ChecksumSize: 4,
				Addr:         1095761920,
				Sums:         "c160817cb5c72bbb",
			},
		},
	}
	var buf bytes.Buffer
	assert.NoError(t, lowmemjson.NewEncoder(&buf).Encode(in))
	assert.Equal(t,
		`{"Addr":13631488,"Size":416033783808,"Runs":[{"Gap":1082130432},{"ChecksumSize":4,"Addr":1095761920,"Sums":"c160817cb5c72bbb"},{"Gap":414951645184}]}`,
		buf.String())
	var out SumRunWithGaps
	assert.NoError(t, lowmemjson.NewDecoder(&buf).Decode(&out))
	assert.Equal(t, in, out)
}

type strEncoder string

func (s strEncoder) EncodeJSON(w io.Writer) error {
	_, err := io.WriteString(w, string(s))
	return err
}

type strMarshaler string

func (s strMarshaler) MarshalJSON() ([]byte, error) {
	return []byte(s), nil
}

type strTextMarshaler struct {
	str string
	err string
}

func (m strTextMarshaler) MarshalText() (txt []byte, err error) {
	if len(m.str) > 0 {
		txt = []byte(m.str)
	}
	if len(m.err) > 0 {
		err = errors.New(m.err)
	}
	return
}

func TestMethodsEncode(t *testing.T) {
	t.Parallel()
	type testcase struct {
		In          string
		ExpectedErr string
	}
	testcases := map[string]testcase{
		"basic": {In: `{}`},
		"empty": {In: ``, ExpectedErr: `syntax error at input byte 0: EOF`},
		"short": {In: `{`, ExpectedErr: `syntax error at input byte 1: unexpected EOF`},
		"long":  {In: `{}{}`, ExpectedErr: `syntax error at input byte 2: invalid character '{' after top-level value`},
	}
	t.Run("encodable", func(t *testing.T) {
		t.Parallel()
		for tcName, tc := range testcases {
			tc := tc
			t.Run(tcName, func(t *testing.T) {
				t.Parallel()
				var buf strings.Builder
				err := lowmemjson.NewEncoder(&buf).Encode([]any{strEncoder(tc.In)})
				if tc.ExpectedErr == "" {
					assert.NoError(t, err)
					assert.Equal(t, "["+tc.In+"]", buf.String())
				} else {
					assert.EqualError(t, err,
						`json: error calling EncodeJSON for type lowmemjson_test.strEncoder: `+
							tc.ExpectedErr)
				}
			})
		}
	})
	t.Run("marshaler", func(t *testing.T) {
		t.Parallel()
		for tcName, tc := range testcases {
			tc := tc
			t.Run(tcName, func(t *testing.T) {
				t.Parallel()
				var buf strings.Builder
				err := lowmemjson.NewEncoder(&buf).Encode([]any{strMarshaler(tc.In)})
				if tc.ExpectedErr == "" {
					assert.NoError(t, err)
					assert.Equal(t, "["+tc.In+"]", buf.String())
				} else {
					assert.EqualError(t, err,
						`json: error calling MarshalJSON for type lowmemjson_test.strMarshaler: `+
							tc.ExpectedErr)
				}
			})
		}
	})
	t.Run("text", func(t *testing.T) {
		t.Parallel()
		type testcase struct {
			Str string
			Err string
		}
		testcases := map[string]testcase{
			"basic": {Str: `a`},
			"err":   {Err: `xxx`},
			"both":  {Str: `a`, Err: `xxx`},
		}
		for tcName, tc := range testcases {
			tc := tc
			t.Run(tcName, func(t *testing.T) {
				t.Parallel()
				var buf strings.Builder
				err := lowmemjson.NewEncoder(&buf).Encode([]any{strTextMarshaler{str: tc.Str, err: tc.Err}})
				if tc.Err == "" {
					assert.NoError(t, err)
					assert.Equal(t, `["`+tc.Str+`"]`, buf.String())
				} else {
					assert.EqualError(t, err,
						`json: error calling MarshalText for type lowmemjson_test.strTextMarshaler: `+
							tc.Err)
					assert.Equal(t, "[", buf.String())
				}
			})
		}
	})
}

type tstDecoder struct {
	n   int
	err string
}

func (d *tstDecoder) DecodeJSON(r io.RuneScanner) error {
	for i := 0; i < d.n; i++ {
		if _, _, err := r.ReadRune(); err != nil {
			if err == io.EOF {
				break
			}
			return err
		}
	}
	if len(d.err) > 0 {
		return errors.New(d.err)
	}
	return nil
}

type strUnmarshaler struct {
	err string
}

func (u *strUnmarshaler) UnmarshalJSON([]byte) error {
	if u.err == "" {
		return nil
	}
	return errors.New(u.err)
}

type textUnmarshaler struct {
	err string
}

func (u *textUnmarshaler) UnmarshalText([]byte) error {
	if u.err == "" {
		return nil
	}
	return errors.New(u.err)
}

type errTextUnmarshaler struct {
	S string
}

func (u *errTextUnmarshaler) UnmarshalText(dat []byte) error {
	u.S = string(dat)
	return errors.New("eee")
}

func TestMethodsDecode(t *testing.T) {
	t.Parallel()
	type testcase struct {
		In          string
		Obj         any
		ExpectedErr string
	}
	testcases := map[string]testcase{
		"decode-basic":           {In: `{}`, Obj: &tstDecoder{n: 2}},
		"decode-basic-eof":       {In: `{}`, Obj: &tstDecoder{n: 5}},
		"decode-syntax-error":    {In: `{x}`, Obj: &tstDecoder{n: 5}, ExpectedErr: `json: v: syntax error at input byte 1: invalid character 'x' looking for beginning of object key string`},
		"unmarshal-syntax-error": {In: `{x}`, Obj: &strUnmarshaler{}, ExpectedErr: `json: v: syntax error at input byte 1: invalid character 'x' looking for beginning of object key string`},
		"decode-short":           {In: `{}`, Obj: &tstDecoder{n: 1}, ExpectedErr: `json: v: cannot decode JSON object at input byte 0 into Go *lowmemjson_test.tstDecoder: did not consume entire object`},
		"decode-err":             {In: `{}`, Obj: &tstDecoder{err: "xxx"}, ExpectedErr: `json: v: cannot decode JSON object at input byte 0 into Go *lowmemjson_test.tstDecoder: xxx`},
		"decode-err2":            {In: `{}`, Obj: &tstDecoder{n: 1, err: "yyy"}, ExpectedErr: `json: v: cannot decode JSON object at input byte 0 into Go *lowmemjson_test.tstDecoder: yyy`},
		"unmarshal-err":          {In: `{}`, Obj: &strUnmarshaler{err: "zzz"}, ExpectedErr: `json: v: cannot decode JSON object at input byte 0 into Go *lowmemjson_test.strUnmarshaler: zzz`},
		"unmarshaltext":          {In: `""`, Obj: &textUnmarshaler{}},
		"unmarshaltext-nonstr":   {In: `{}`, Obj: &textUnmarshaler{}, ExpectedErr: `json: v: cannot decode JSON object at input byte 0 into Go *lowmemjson_test.textUnmarshaler`},
		"unmarshaltext-err":      {In: `""`, Obj: &textUnmarshaler{err: "zzz"}, ExpectedErr: `json: v: cannot decode JSON string at input byte 0 into Go *lowmemjson_test.textUnmarshaler: zzz`},
		"unmarshaltext-mapkey":   {In: `{"a":1}`, Obj: new(map[errTextUnmarshaler]int), ExpectedErr: `json: v: cannot decode JSON string at input byte 1 into Go *lowmemjson_test.errTextUnmarshaler: eee`},
	}
	for tcName, tc := range testcases {
		tc := tc
		t.Run(tcName, func(t *testing.T) {
			t.Parallel()
			obj := tc.Obj
			err := lowmemjson.NewDecoder(strings.NewReader(tc.In)).Decode(&obj)
			if tc.ExpectedErr == "" {
				assert.NoError(t, err)
			} else {
				assert.EqualError(t, err, tc.ExpectedErr)
			}
		})
	}
}