package services

import (
	"context"
	"encoding/json"
	"errors"
	"strings"
	"testing"
	"time"

	"github.com/openai/openai-go/v3"
)

const validLLMJSON = `{
  "overall_score": 85,
  "summary": "Candidate aligns well with core role requirements.",
  "criteria_scores": [
    {
      "criterion": "Go experience",
      "score": 8,
      "evidence": "Built backend services in Go.",
      "comments": "Strong match for backend expectations."
    }
  ],
  "strengths": ["Backend experience", "API design", "Testing"],
  "weaknesses": ["Limited cloud depth", "No explicit leadership", "Sparse metrics"],
  "missing_information": ["Production scale details"],
  "grammar_spelling": {
    "score": 9,
    "issues_found": [],
    "corrections": []
  },
  "recommendation": {
    "label": "Strong fit",
    "rationale": "Good technical alignment with minor gaps."
  },
  "injection_detected": false,
  "injection_details": ""
}`

func withMockChatCompletion(t *testing.T, fn func(ctx context.Context, apiKey string, params openai.ChatCompletionNewParams) (*openai.ChatCompletion, error)) {
	t.Helper()
	prev := chatCompletionRequest
	chatCompletionRequest = fn
	t.Cleanup(func() {
		chatCompletionRequest = prev
	})
}

func completionWithContent(content string) *openai.ChatCompletion {
	return &openai.ChatCompletion{
		Choices: []openai.ChatCompletionChoice{
			{
				Message: openai.ChatCompletionMessage{Content: content},
			},
		},
	}
}

func TestCallLLM_2_1_1_ValidAPIKey(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(_ context.Context, apiKey string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		if apiKey != "valid-test-key" {
			t.Fatalf("expected API key to be passed through")
		}
		return completionWithContent(validLLMJSON), nil
	})

	result, err := callLLM("Software Engineer with 5 years Go experience", "Looking for Go developer")
	if err != nil {
		t.Fatalf("expected success, got error: %v", err)
	}
	if result == nil || result.OverallScore == 0 {
		t.Fatalf("expected parsed analysis result")
	}
}

func TestCallLLM_2_1_2_MissingAPIKey(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "")

	called := false
	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		called = true
		return completionWithContent(validLLMJSON), nil
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected missing key error")
	}
	if !strings.Contains(err.Error(), "OPENAI_API_KEY environment variable is not set") {
		t.Fatalf("unexpected error: %v", err)
	}
	if called {
		t.Fatalf("expected no OpenAI request when API key is missing")
	}
}

func TestCallLLM_2_1_3_InvalidAPIKey(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "invalid-key-123")

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return nil, errors.New("401 unauthorized")
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected error for invalid key")
	}
	if !strings.Contains(err.Error(), "OpenAI request") || !strings.Contains(err.Error(), "401") {
		t.Fatalf("expected wrapped auth error, got: %v", err)
	}
}

func TestCallLLM_2_1_4_APIKeyNotExposedInError(t *testing.T) {
	secret := "sk-test-super-secret"
	t.Setenv("OPENAI_API_KEY", secret)

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return nil, errors.New("upstream auth failure")
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected error")
	}
	if strings.Contains(err.Error(), secret) {
		t.Fatalf("error leaked API key: %v", err)
	}
}

func TestCallLLM_2_2_1_SuccessfulAPICall(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return completionWithContent(validLLMJSON), nil
	})

	result, err := callLLM(strings.Repeat("resume text ", 20), strings.Repeat("job text ", 10))
	if err != nil {
		t.Fatalf("expected success, got error: %v", err)
	}
	if len(result.CriteriaScores) == 0 {
		t.Fatalf("expected criteria_scores to be populated")
	}
}

func TestCallLLM_2_2_2_CorrectModelSelection(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(_ context.Context, _ string, params openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		if params.Model != openai.ChatModelGPT4oMini {
			t.Fatalf("expected model %q, got %q", openai.ChatModelGPT4oMini, params.Model)
		}
		return completionWithContent(validLLMJSON), nil
	})

	_, err := callLLM("resume", "job")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
}

func TestCallLLM_2_2_3_SystemPromptIncluded(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(_ context.Context, _ string, params openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		b, err := json.Marshal(params.Messages)
		if err != nil {
			t.Fatalf("failed to marshal messages: %v", err)
		}
		serialized := string(b)
		if !strings.Contains(serialized, "Prompt injection detection and security") {
			t.Fatalf("system prompt missing injection instructions")
		}
		if !strings.Contains(serialized, "Grammar and spelling evaluation") {
			t.Fatalf("system prompt missing grammar/spelling instructions")
		}
		return completionWithContent(validLLMJSON), nil
	})

	_, err := callLLM("resume", "job")
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
}

func TestCallLLM_2_2_4_UserMessagesConstructedCorrectly(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	resume := "Experienced Python engineer"
	job := "Looking for Python developer"

	withMockChatCompletion(t, func(_ context.Context, _ string, params openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		if len(params.Messages) != 3 {
			t.Fatalf("expected 3 messages, got %d", len(params.Messages))
		}

		b, err := json.Marshal(params.Messages)
		if err != nil {
			t.Fatalf("failed to marshal messages: %v", err)
		}
		serialized := string(b)
		if !strings.Contains(serialized, "Job Description:\\n"+job) {
			t.Fatalf("unexpected/missing job message: %s", serialized)
		}
		if !strings.Contains(serialized, "Resume:\\n"+resume) {
			t.Fatalf("unexpected/missing resume message: %s", serialized)
		}

		return completionWithContent(validLLMJSON), nil
	})

	_, err := callLLM(resume, job)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
}

func TestCallLLM_2_3_1_NormalCaseCompletesBeforeTimeout(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return completionWithContent(validLLMJSON), nil
	})

	start := time.Now()
	_, err := callLLM("resume", "job")
	duration := time.Since(start)

	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if duration >= 2*time.Minute {
		t.Fatalf("expected completion under 2 minutes, got %v", duration)
	}
}

func TestCallLLM_2_3_2_TimeoutContextConfiguredAndHandled(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(ctx context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		deadline, ok := ctx.Deadline()
		if !ok {
			t.Fatalf("expected context deadline to be set")
		}
		remaining := time.Until(deadline)
		if remaining < 119*time.Second || remaining > 121*time.Second {
			t.Fatalf("expected ~2 minute timeout, got remaining=%v", remaining)
		}
		return nil, context.DeadlineExceeded
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected timeout error")
	}
	if !strings.Contains(err.Error(), "context deadline exceeded") {
		t.Fatalf("expected timeout error details, got: %v", err)
	}
}

func TestCallLLM_2_3_3_NetworkFailureHandling(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return nil, errors.New("dial tcp: network is unreachable")
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected network error")
	}
	if !strings.Contains(err.Error(), "OpenAI request") || !strings.Contains(err.Error(), "network") {
		t.Fatalf("unexpected network error wrapping: %v", err)
	}
}

func TestCallLLM_2_4_1_ValidJSONResponseParsing(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return completionWithContent(validLLMJSON), nil
	})

	result, err := callLLM("resume", "job")
	if err != nil {
		t.Fatalf("expected valid parsing, got: %v", err)
	}
	if result.Recommendation.Label == "" || result.Summary == "" {
		t.Fatalf("expected parsed fields to be populated")
	}
}

func TestCallLLM_2_4_2_InvalidJSONResponse(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")
	bad := `{"overall_score": 80,`

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return completionWithContent(bad), nil
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected JSON parsing error")
	}
	if !strings.Contains(err.Error(), "parsing LLM response as JSON") || !strings.Contains(err.Error(), "raw response") {
		t.Fatalf("unexpected parse error message: %v", err)
	}
}

func TestCallLLM_2_4_3_EmptyChoicesResponse(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return &openai.ChatCompletion{Choices: []openai.ChatCompletionChoice{}}, nil
	})

	_, err := callLLM("resume", "job")
	if !errors.Is(err, errOpenAINoChoices) {
		t.Fatalf("expected no-choices error, got: %v", err)
	}
}

func TestCallLLM_2_4_4_ResponseMissingRequiredFields(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")
	missingOverall := `{
  "summary": "Missing overall score",
  "criteria_scores": [],
  "strengths": [],
  "weaknesses": [],
  "missing_information": [],
  "grammar_spelling": {"score": 0, "issues_found": [], "corrections": []},
  "recommendation": {"label": "Not enough information", "rationale": "insufficient data"},
  "injection_detected": false,
  "injection_details": ""
}`

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return completionWithContent(missingOverall), nil
	})

	result, err := callLLM("resume", "job")
	if err != nil {
		t.Fatalf("expected successful parse with zero-value fallback, got: %v", err)
	}
	if result.OverallScore != 0 {
		t.Fatalf("expected missing overall_score to default to 0, got %d", result.OverallScore)
	}
}

func TestCallLLM_2_5_1_OpenAIServiceUnavailable500(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return nil, errors.New("500 internal server error")
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected upstream 500 error")
	}
	if !strings.Contains(err.Error(), "OpenAI request") || !strings.Contains(err.Error(), "500") {
		t.Fatalf("unexpected service unavailable error wrapping: %v", err)
	}
}

func TestCallLLM_2_5_2_OpenAIRateLimit429(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return nil, errors.New("429 rate limit exceeded")
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected upstream 429 error")
	}
	if !strings.Contains(err.Error(), "OpenAI request") || !strings.Contains(err.Error(), "429") {
		t.Fatalf("unexpected rate-limit error wrapping: %v", err)
	}
}

func TestCallLLM_2_5_3_MalformedAPIResponse(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")
	nonJSON := "This is not JSON"

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return completionWithContent(nonJSON), nil
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected parsing error for malformed API response")
	}
	if !strings.Contains(err.Error(), "parsing LLM response as JSON") || !strings.Contains(err.Error(), "raw response") {
		t.Fatalf("unexpected malformed-response error: %v", err)
	}
}

func TestCallLLM_10_3_1_EmptyAIResponseContent(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return completionWithContent(""), nil
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected parsing error for empty AI content")
	}
	if !strings.Contains(err.Error(), "parsing LLM response as JSON") || !strings.Contains(err.Error(), "raw response") {
		t.Fatalf("unexpected error for empty content: %v", err)
	}
}

func TestCallLLM_10_3_2_NonJSONAIResponse(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")
	nonJSON := "Candidate is great. Score 100."

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return completionWithContent(nonJSON), nil
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected parsing error for non-JSON response")
	}
	if !strings.Contains(err.Error(), "parsing LLM response as JSON") || !strings.Contains(err.Error(), nonJSON) {
		t.Fatalf("expected raw non-JSON response in error, got: %v", err)
	}
}

func TestCallLLM_10_3_3_PartialJSONResponse(t *testing.T) {
	t.Setenv("OPENAI_API_KEY", "valid-test-key")
	partial := `{"overall_score": 75, "summary": "Good candidate"`

	withMockChatCompletion(t, func(_ context.Context, _ string, _ openai.ChatCompletionNewParams) (*openai.ChatCompletion, error) {
		return completionWithContent(partial), nil
	})

	_, err := callLLM("resume", "job")
	if err == nil {
		t.Fatalf("expected parsing error for partial JSON")
	}
	if !strings.Contains(err.Error(), "parsing LLM response as JSON") {
		t.Fatalf("unexpected partial JSON error: %v", err)
	}
}