// Package faultRecordFile 故障录波数据解析（纯函数）：cmd=0 的 hexData、cmd=2 导出的 failuredata／waveformdata 及压缩包。
//
// 字节结构依据 docs/fault-record/FaultFilter_MQTT协议文档.md 5.1.1、5.2，
// 并按 docs/fault-record/protocol-specification.md 8A 的样本验证规则补充。
package faultRecordFile

import (
	"bytes"
	"encoding/binary"
	"fmt"

	proto "fwh-toolbox-server/function/FaultRecordProtocol"
)

// byteReader 顺序读取，越界时记录错误并返回零值
type byteReader struct {
	b   []byte
	p   int
	err error
}

func (r *byteReader) take(n int, field string) []byte {
	if r.err != nil {
		return make([]byte, n)
	}
	if r.p+n > len(r.b) {
		r.err = fmt.Errorf("data too short at %s (offset %d, need %d, have %d)", field, r.p, n, len(r.b)-r.p)
		return make([]byte, n)
	}
	v := r.b[r.p : r.p+n]
	r.p += n
	return v
}

func (r *byteReader) u8(field string) uint8   { return r.take(1, field)[0] }
func (r *byteReader) u16(field string) uint16 { return binary.BigEndian.Uint16(r.take(2, field)) }
func (r *byteReader) u32(field string) uint32 { return binary.BigEndian.Uint32(r.take(4, field)) }
func (r *byteReader) time(field string) proto.DeviceTime {
	return proto.ParseDeviceTime(r.take(7, field))
}

// cString 取第一个 NUL 之前的内容
func cString(b []byte) string {
	if i := bytes.IndexByte(b, 0); i >= 0 {
		b = b[:i]
	}
	return string(b)
}

/************** 公共结构 **************/

// BasicInfo 设备故障录波功能基本信息（code=2，16 字节）
type BasicInfo struct {
	CanProtocolVersion uint8  `json:"canProtocolVersion"`
	StorageFormat      uint8  `json:"storageFormat"`
	ParamListVersion   string `json:"paramListVersion"` // 4 字节十六进制
	MaxSampleFrequency uint16 `json:"maxSampleFrequency"`
	SampleFrequency    uint16 `json:"sampleFrequency"`
	TotalPoints        uint16 `json:"totalPoints"`
	PrePoints          uint16 `json:"prePoints"`
	PostPoints         uint16 `json:"postPoints"`
}

func readBasicInfo(r *byteReader) BasicInfo {
	return BasicInfo{
		CanProtocolVersion: r.u8("canProtocolVersion"),
		StorageFormat:      r.u8("storageFormat"),
		ParamListVersion:   fmt.Sprintf("%08X", r.u32("paramListVersion")),
		MaxSampleFrequency: r.u16("maxSampleFrequency"),
		SampleFrequency:    r.u16("sampleFrequency"),
		TotalPoints:        r.u16("totalPoints"),
		PrePoints:          r.u16("prePoints"),
		PostPoints:         r.u16("postPoints"),
	}
}

// SnapshotChannel 快照通道：含义代码（F14），code=4 中带故障时刻的原始值
type SnapshotChannel struct {
	Meaning uint16  `json:"meaning"`
	Value   *uint16 `json:"value,omitempty"`
}

// ConfigurableChannel 可配通道：类型 2B + 数据 4B。
// 类型低字节与设置 id=6 的类型字节格式一致：高 4 位为设置方式（0=默认方式 1=代码方式），低 4 位为地址类型；
// 两种方式的数据都按 4 字节原样保留在 Address（代码方式时前 2 字节为参数代码）。
type ConfigurableChannel struct {
	Type     uint16 `json:"type"`
	Mode     uint8  `json:"mode"`
	AddrType uint8  `json:"addrType"`
	TypeName string `json:"typeName"`
	Address  uint32 `json:"address"`
}

// ChannelGroups 快照 / 采样 / 可配快照 / 可配采样 四组通道（code=1 与 failuredata 共用）
type ChannelGroups struct {
	SnapshotTotal     uint8                 `json:"snapshotTotal"`
	SnapshotUsed      uint8                 `json:"snapshotUsed"`
	Snapshots         []SnapshotChannel     `json:"snapshots"`
	SampleTotal       uint8                 `json:"sampleTotal"`
	SampleUsed        uint8                 `json:"sampleUsed"`
	SampleMeanings    []uint16              `json:"sampleMeanings"`
	ConfigSnapTotal   uint8                 `json:"configSnapTotal"`
	ConfigSnapUsed    uint8                 `json:"configSnapUsed"`
	ConfigSnapshots   []ConfigurableChannel `json:"configSnapshots"`
	ConfigSampleTotal uint8                 `json:"configSampleTotal"`
	ConfigSampleUsed  uint8                 `json:"configSampleUsed"`
	ConfigSamples     []ConfigurableChannel `json:"configSamples"`
}

func readChannelGroups(r *byteReader, snapshotWithValue bool) ChannelGroups {
	var g ChannelGroups
	g.SnapshotTotal = r.u8("snapshotTotal")
	g.SnapshotUsed = r.u8("snapshotUsed")
	g.Snapshots = make([]SnapshotChannel, 0, g.SnapshotTotal)
	for i := 0; i < int(g.SnapshotTotal); i++ {
		c := SnapshotChannel{Meaning: r.u16("snapshotMeaning")}
		if snapshotWithValue {
			v := r.u16("snapshotValue")
			c.Value = &v
		}
		g.Snapshots = append(g.Snapshots, c)
	}

	g.SampleTotal = r.u8("sampleTotal")
	g.SampleUsed = r.u8("sampleUsed")
	g.SampleMeanings = make([]uint16, 0, g.SampleTotal)
	for i := 0; i < int(g.SampleTotal); i++ {
		g.SampleMeanings = append(g.SampleMeanings, r.u16("sampleMeaning"))
	}

	g.ConfigSnapTotal = r.u8("configSnapTotal")
	g.ConfigSnapUsed = r.u8("configSnapUsed")
	g.ConfigSnapshots = readConfigurable(r, int(g.ConfigSnapTotal))

	g.ConfigSampleTotal = r.u8("configSampleTotal")
	g.ConfigSampleUsed = r.u8("configSampleUsed")
	g.ConfigSamples = readConfigurable(r, int(g.ConfigSampleTotal))
	return g
}

func readConfigurable(r *byteReader, n int) []ConfigurableChannel {
	list := make([]ConfigurableChannel, 0, n)
	for i := 0; i < n; i++ {
		t := r.u16("configType")
		mode, addrType := uint8(t)>>4, uint8(t)&0x0F
		list = append(list, ConfigurableChannel{
			Type:     t,
			Mode:     mode,
			AddrType: addrType,
			TypeName: proto.ChannelAddrTypeNames[addrType],
			Address:  r.u32("configAddress"),
		})
	}
	return list
}