package output

import (
	"encoding/json"
	"fmt"
	"io"

	"github.com/salvacybersec/keyhunter/pkg/engine"
)

func init() {
	Register("sarif", SARIFFormatter{})
}

// SARIFFormatter emits SARIF 2.1.0 JSON suitable for GitHub code scanning
// uploads and other CI/CD ingestion pipelines.
//
// The implementation uses hand-rolled structs rather than an external library
// per project convention (see CLAUDE.md). Only the subset of the SARIF 2.1.0
// schema required for code-scanning uploads is modeled; this keeps the
// surface area small (~150 LoC) while producing documents that GitHub and
// other SARIF consumers accept as valid.
type SARIFFormatter struct{}

// sarifDoc is the top-level SARIF 2.1.0 document.
type sarifDoc struct {
	Schema  string     `json:"$schema"`
	Version string     `json:"version"`
	Runs    []sarifRun `json:"runs"`
}

type sarifRun struct {
	Tool    sarifTool     `json:"tool"`
	Results []sarifResult `json:"results"`
}

type sarifTool struct {
	Driver sarifDriver `json:"driver"`
}

type sarifDriver struct {
	Name    string      `json:"name"`
	Version string      `json:"version"`
	Rules   []sarifRule `json:"rules"`
}

type sarifRule struct {
	ID               string    `json:"id"`
	Name             string    `json:"name"`
	ShortDescription sarifText `json:"shortDescription"`
}

type sarifText struct {
	Text string `json:"text"`
}

type sarifResult struct {
	RuleID    string          `json:"ruleId"`
	Level     string          `json:"level"`
	Message   sarifText       `json:"message"`
	Locations []sarifLocation `json:"locations"`
}

type sarifLocation struct {
	PhysicalLocation sarifPhysicalLocation `json:"physicalLocation"`
}

type sarifPhysicalLocation struct {
	ArtifactLocation sarifArtifactLocation `json:"artifactLocation"`
	Region           sarifRegion           `json:"region"`
}

type sarifArtifactLocation struct {
	URI string `json:"uri"`
}

type sarifRegion struct {
	StartLine int `json:"startLine"`
}

// Format implements the Formatter interface. It produces a SARIF 2.1.0
// document with one rule per distinct provider and one result per finding.
// The output is always a valid SARIF document, even when findings is empty.
func (SARIFFormatter) Format(findings []engine.Finding, w io.Writer, opts Options) error {
	toolName := opts.ToolName
	if toolName == "" {
		toolName = "keyhunter"
	}
	toolVersion := opts.ToolVersion
	if toolVersion == "" {
		toolVersion = "dev"
	}

	// Dedup rules by provider name, preserving first-seen order so that the
	// output is deterministic for a given input slice.
	seen := map[string]bool{}
	rules := make([]sarifRule, 0)
	for _, f := range findings {
		if seen[f.ProviderName] {
			continue
		}
		seen[f.ProviderName] = true
		rules = append(rules, sarifRule{
			ID:               f.ProviderName,
			Name:             f.ProviderName,
			ShortDescription: sarifText{Text: fmt.Sprintf("Leaked %s API key", f.ProviderName)},
		})
	}

	results := make([]sarifResult, 0, len(findings))
	for _, f := range findings {
		key := f.KeyMasked
		if opts.Unmask {
			key = f.KeyValue
		}
		// SARIF requires startLine >= 1. Floor any non-positive line numbers
		// (which occur for stdin/URL sources or when line tracking is absent).
		startLine := f.LineNumber
		if startLine < 1 {
			startLine = 1
		}
		results = append(results, sarifResult{
			RuleID:  f.ProviderName,
			Level:   sarifLevel(f.Confidence),
			Message: sarifText{Text: fmt.Sprintf("Detected %s key (%s): %s", f.ProviderName, f.Confidence, key)},
			Locations: []sarifLocation{{
				PhysicalLocation: sarifPhysicalLocation{
					ArtifactLocation: sarifArtifactLocation{URI: f.Source},
					Region:           sarifRegion{StartLine: startLine},
				},
			}},
		})
	}

	doc := sarifDoc{
		Schema:  "https://json.schemastore.org/sarif-2.1.0.json",
		Version: "2.1.0",
		Runs: []sarifRun{{
			Tool: sarifTool{Driver: sarifDriver{
				Name:    toolName,
				Version: toolVersion,
				Rules:   rules,
			}},
			Results: results,
		}},
	}

	enc := json.NewEncoder(w)
	enc.SetIndent("", "  ")
	return enc.Encode(doc)
}

// sarifLevel maps KeyHunter confidence strings to SARIF result levels.
// Unknown confidence values fall back to "warning" so that unexpected input
// never produces an invalid SARIF document.
func sarifLevel(confidence string) string {
	switch confidence {
	case "high":
		return "error"
	case "medium":
		return "warning"
	case "low":
		return "note"
	default:
		return "warning"
	}
}