package main

import (
	"bytes"
	"encoding/base64"
	"encoding/json"
	"errors"
	"io"
	"os"
	"strings"

	"git.ipao.vip/rogee/go-sip/internal/ai"
)

const maxApprovedMockScenarioBytes = 4 << 20

type approvedMockScenario struct {
	InboundPCM16      []byte
	Script            ai.ApprovedMockScript
	MaxWAVBytes       int64
	ExpectedRecording bool
	Outcome           string
	ReasonMessage     string
}

// loadApprovedMockScenario reads only explicit synthetic media facts. It does
// not read or override the AI business configuration delivered by Dispatcher.
func loadApprovedMockScenario(path string) (approvedMockScenario, error) {
	if strings.TrimSpace(path) == "" {
		return approvedMockScenario{}, errors.New("AGENT_MOCK_SCENARIO_FILE is required")
	}
	file, err := os.Open(path)
	if err != nil {
		return approvedMockScenario{}, errors.New("AGENT_MOCK_SCENARIO_FILE cannot be opened")
	}
	defer file.Close()
	data, err := io.ReadAll(io.LimitReader(file, maxApprovedMockScenarioBytes+1))
	if err != nil || len(data) > maxApprovedMockScenarioBytes {
		return approvedMockScenario{}, errors.New("AGENT_MOCK_SCENARIO_FILE exceeds its size limit or cannot be read")
	}
	var encoded struct {
		InboundPCM16      *string                `json:"inbound_pcm16"`
		Script            *ai.ApprovedMockScript `json:"script"`
		MaxWAVBytes       *int64                 `json:"max_wav_bytes"`
		ExpectedRecording *bool                  `json:"expected_recording"`
		Outcome           *string                `json:"outcome"`
		ReasonMessage     *string                `json:"reason_message"`
	}
	decoder := json.NewDecoder(bytes.NewReader(data))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&encoded); err != nil {
		return approvedMockScenario{}, errors.New("AGENT_MOCK_SCENARIO_FILE has invalid fields")
	}
	if err := decoder.Decode(new(any)); err != io.EOF {
		return approvedMockScenario{}, errors.New("AGENT_MOCK_SCENARIO_FILE contains extra data")
	}
	if encoded.InboundPCM16 == nil || encoded.Script == nil || encoded.MaxWAVBytes == nil || encoded.ExpectedRecording == nil || encoded.Outcome == nil || encoded.ReasonMessage == nil {
		return approvedMockScenario{}, errors.New("AGENT_MOCK_SCENARIO_FILE requires explicit media, script, outcome and recording facts")
	}
	pcm, err := base64.StdEncoding.DecodeString(*encoded.InboundPCM16)
	if err != nil || len(encoded.Script.Turns) == 0 || *encoded.MaxWAVBytes <= 44 || strings.TrimSpace(*encoded.ReasonMessage) == "" ||
		(*encoded.Outcome != "answered" && *encoded.Outcome != "no_answer" && *encoded.Outcome != "failed") {
		return approvedMockScenario{}, errors.New("AGENT_MOCK_SCENARIO_FILE has invalid synthetic media or outcome")
	}
	return approvedMockScenario{
		InboundPCM16: pcm, Script: *encoded.Script, MaxWAVBytes: *encoded.MaxWAVBytes,
		ExpectedRecording: *encoded.ExpectedRecording, Outcome: *encoded.Outcome, ReasonMessage: *encoded.ReasonMessage,
	}, nil
}