package analysis

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"time"
	"unicode"

	"gitea.wayfinderak.com/wayfinderak/log-guardian/internal/loki"
	"gitea.wayfinderak.com/wayfinderak/log-guardian/internal/store"
)

type Finding struct {
	Summary            string   `json:"summary"`
	RecommendedActions []string `json:"recommended_actions,omitempty"`
	Confidence         string   `json:"confidence"`
}

type Analyzer interface {
	Analyze(ctx context.Context, rule store.Rule, matches []loki.Match) (Finding, error)
}

type NoopAnalyzer struct{}

func (NoopAnalyzer) Analyze(ctx context.Context, rule store.Rule, matches []loki.Match) (Finding, error) {
	_ = ctx
	return Finding{Summary: summarize(rule, matches), Confidence: "rule-only"}, nil
}

type OllamaAnalyzer struct {
	URL   string
	Model string
	http  *http.Client
}

func NewOllamaAnalyzer(url, model string) *OllamaAnalyzer {
	return &OllamaAnalyzer{URL: strings.TrimRight(url, "/"), Model: model, http: &http.Client{Timeout: 60 * time.Second}}
}

func (a *OllamaAnalyzer) Analyze(ctx context.Context, rule store.Rule, matches []loki.Match) (Finding, error) {
	if a.URL == "" || a.Model == "" {
		return NoopAnalyzer{}.Analyze(ctx, rule, matches)
	}
	prompt := buildPrompt(rule, matches)
	body, _ := json.Marshal(map[string]any{"model": a.Model, "prompt": prompt, "stream": false})
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, a.URL+"/api/generate", bytes.NewReader(body))
	if err != nil {
		return Finding{}, err
	}
	req.Header.Set("Content-Type", "application/json")
	resp, err := a.http.Do(req)
	if err != nil {
		return Finding{}, err
	}
	defer resp.Body.Close()
	if resp.StatusCode < 200 || resp.StatusCode > 299 {
		return Finding{}, fmt.Errorf("ollama analysis failed: status %d", resp.StatusCode)
	}
	var raw struct {
		Response string `json:"response"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&raw); err != nil {
		return Finding{}, err
	}
	summary := strings.TrimSpace(raw.Response)
	if summary == "" {
		return NoopAnalyzer{}.Analyze(ctx, rule, matches)
	}
	if len(summary) > 500 {
		summary = summary[:500] + "..."
	}
	return Finding{Summary: summary, Confidence: "ollama-local"}, nil
}

func buildPrompt(rule store.Rule, matches []loki.Match) string {
	var b strings.Builder
	b.WriteString("You are analyzing private application logs locally. Summarize likely cause and operator next steps in 4 concise sentences or fewer. Do not suggest destructive actions.\n")
	b.WriteString("Rule: ")
	b.WriteString(rule.Name)
	b.WriteString("\nSeverity: ")
	b.WriteString(rule.Severity)
	b.WriteString("\nSanitized samples:\n")
	limit := len(matches)
	if limit > 5 {
		limit = 5
	}
	for i := 0; i < limit; i++ {
		line := sanitizeLine(matches[i].Line)
		line = redactSecrets(line)
		if len(line) > 300 {
			line = line[:300] + "..."
		}
		b.WriteString("- ")
		b.WriteString(line)
		b.WriteByte('\n')
	}
	return b.String()
}

func summarize(rule store.Rule, matches []loki.Match) string {
	if len(matches) == 0 {
		return "No matching log entries."
	}
	line := redactSecrets(sanitizeLine(matches[0].Line))
	if len(line) > 180 {
		line = line[:180] + "..."
	}
	return rule.Name + " matched " + plural(len(matches), "log entry", "log entries") + "; first match: " + line
}

func sanitizeLine(line string) string {
	line = strings.ReplaceAll(line, "\n", " ")
	line = strings.ReplaceAll(line, "\r", " ")
	return strings.TrimSpace(line)
}

func redactSecrets(line string) string {
	fields := strings.Fields(line)
	for i, field := range fields {
		lower := strings.ToLower(field)
		if strings.Contains(lower, "token=") || strings.Contains(lower, "password=") || strings.Contains(lower, "secret=") || strings.Contains(lower, "apikey=") || strings.Contains(lower, "api_key=") || strings.HasPrefix(lower, "bearer") {
			fields[i] = redactField(field)
		}
	}
	return strings.Join(fields, " ")
}

func redactField(field string) string {
	idx := strings.IndexAny(field, "=:")
	if idx < 0 {
		return "[REDACTED]"
	}
	prefix := strings.TrimRightFunc(field[:idx], func(r rune) bool { return unicode.IsSpace(r) })
	return prefix + "=[REDACTED]"
}

func plural(count int, singular, plural string) string {
	if count == 1 {
		return "1 " + singular
	}
	return strconvItoa(count) + " " + plural
}

func strconvItoa(i int) string {
	if i == 0 {
		return "0"
	}
	var b [20]byte
	bp := len(b)
	for i > 0 {
		bp--
		b[bp] = byte('0' + i%10)
		i /= 10
	}
	return string(b[bp:])
}