// Package utils provides shared functionality for dumping CT log tile entries.
// (C) Copyright 2026 Pim van Pelt <pim@ipng.ch>
package utils

import (
	"bytes"
	"compress/gzip"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"

	"filippo.io/sunlight"
)

const maxCompressRatio = 100

// FetchURL fetches data from a URL.
func FetchURL(url string) ([]byte, error) {
	resp, err := http.Get(url)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("HTTP %d", resp.StatusCode)
	}

	return io.ReadAll(resp.Body)
}

// Decompress decompresses gzip-compressed data, or returns the data as-is if not compressed.
func Decompress(data []byte) ([]byte, error) {
	r, err := gzip.NewReader(bytes.NewReader(data))
	if err != nil {
		// Not gzipped, return as-is
		return data, nil
	}
	maxSize := int64(len(data)) * maxCompressRatio
	return io.ReadAll(io.LimitReader(r, maxSize))
}

// DumpAllEntries reads and dumps all entries from tile data.
func DumpAllEntries(tileData []byte) error {
	entryNum := 0
	for len(tileData) > 0 {
		e, remaining, err := sunlight.ReadTileLeaf(tileData)
		if err != nil {
			return fmt.Errorf("failed to read entry %d: %w", entryNum, err)
		}
		tileData = remaining

		dumpEntry(e, entryNum)
		fmt.Println()
		entryNum++
	}

	fmt.Printf("Total entries: %d\n", entryNum)
	return nil
}

// DumpEntryAtPosition reads and dumps a specific entry at the given position.
func DumpEntryAtPosition(tileData []byte, position int, expectedIndex int64) error {
	entryNum := 0
	for len(tileData) > 0 {
		e, remaining, err := sunlight.ReadTileLeaf(tileData)
		if err != nil {
			return fmt.Errorf("failed to read entry %d: %w", entryNum, err)
		}
		tileData = remaining

		if entryNum == position {
			if e.LeafIndex != expectedIndex {
				fmt.Fprintf(os.Stderr, "WARNING: Expected leaf index %d but found %d at position %d\n",
					expectedIndex, e.LeafIndex, position)
			}
			dumpEntry(e, entryNum)
			return nil
		}
		entryNum++
	}

	return fmt.Errorf("position %d not found in tile (only %d entries)", position, entryNum)
}

func dumpEntry(e *sunlight.LogEntry, entryNum int) {
	fmt.Printf("=== Entry %d ===\n", entryNum)
	fmt.Printf("Leaf Index: %d\n", e.LeafIndex)
	fmt.Printf("Timestamp: %d\n", e.Timestamp)
	fmt.Printf("Is Precert: %v\n", e.IsPrecert)

	if e.IsPrecert {
		fmt.Printf("Issuer Key Hash: %x\n", e.IssuerKeyHash)
	}

	fmt.Printf("Certificate: %d bytes\n", len(e.Certificate))
	if e.PreCertificate != nil {
		fmt.Printf("PreCertificate: %d bytes\n", len(e.PreCertificate))
	}

	fmt.Printf("Chain Fingerprints: %d entries\n", len(e.ChainFingerprints))
	for i, fp := range e.ChainFingerprints {
		fmt.Printf("  [%d]: %x\n", i, fp)
	}

	// Try to extract parsed certificate info
	if trimmed, err := e.TrimmedEntry(); err == nil {
		if data, err := json.MarshalIndent(trimmed, "  ", "  "); err == nil {
			fmt.Printf("Parsed Certificate Info:\n  %s\n", data)
		}
	}
}