package tide

import (
	"encoding/json"
	"fmt"
	"regexp"
	"strings"
)

var carbonOffsetRe = regexp.MustCompile(`^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\+00:00$`)

const (
	maskDatetime = "<datetime>"
	maskID       = "<id>"
)

func normalizeJSON(raw []byte, step Step) ([]byte, []Diff) {
	if len(strings.TrimSpace(string(raw))) == 0 {
		return raw, nil
	}
	val, err := decodeJSON(raw)
	if err != nil {
		return raw, nil
	}
	var diffs []Diff
	masked := maskValue("$", val, step, &diffs)
	out, err := json.Marshal(masked)
	if err != nil {
		return raw, diffs
	}
	return out, diffs
}

func maskValue(path string, val any, step Step, diffs *[]Diff) any {
	switch v := val.(type) {
	case map[string]any:
		out := make(map[string]any, len(v))
		for k, child := range v {
			out[k] = maskValue(pathJoin(path, k), child, step, diffs)
		}
		return out
	case []any:
		out := make([]any, len(v))
		for i, child := range v {
			out[i] = maskValue(fmt.Sprintf("%s[%d]", path, i), child, step, diffs)
		}
		return out
	default:
		return maskLeaf(path, val, step, diffs)
	}
}

func maskLeaf(path string, val any, step Step, diffs *[]Diff) any {
	key := lastPathKey(path)
	if key == "slug" || disabledPath(step, path, key) {
		return val
	}
	if isDateKey(key) {
		return maskDate(path, val, diffs)
	}
	if isIDKey(key) {
		return maskIDValue(path, val, diffs)
	}
	return val
}

func maskDate(path string, val any, diffs *[]Diff) any {
	if val == nil {
		return nil
	}
	s, ok := val.(string)
	if !ok {
		*diffs = append(*diffs, Diff{Path: path, Expected: "Carbon +00:00 string or null", Actual: formatValue(val)})
		return val
	}
	if !carbonOffsetRe.MatchString(s) {
		*diffs = append(*diffs, Diff{Path: path, Expected: "Carbon +00:00", Actual: strconvQuote(s)})
		return val
	}
	return maskDatetime
}

func maskIDValue(path string, val any, diffs *[]Diff) any {
	n, ok := val.(json.Number)
	if !ok {
		*diffs = append(*diffs, Diff{Path: path, Expected: "integer id", Actual: formatValue(val)})
		return val
	}
	if strings.Contains(string(n), ".") {
		*diffs = append(*diffs, Diff{Path: path, Expected: "integer id", Actual: "number " + string(n)})
		return val
	}
	return maskID
}

func isDateKey(key string) bool {
	return strings.HasSuffix(key, "_at")
}

func isIDKey(key string) bool {
	if key == "id" {
		return true
	}
	return strings.HasSuffix(key, "_id") && !strings.HasSuffix(key, "_at")
}

func lastPathKey(path string) string {
	path = strings.TrimPrefix(path, "$.")
	if i := strings.LastIndex(path, "."); i >= 0 {
		path = path[i+1:]
	}
	if i := strings.IndexByte(path, '['); i >= 0 {
		path = path[:i]
	}
	return path
}

func disabledPath(step Step, jsonPath, key string) bool {
	for _, rule := range step.Normalize {
		if !rule.Disable {
			continue
		}
		p := strings.TrimSpace(rule.Path)
		if p == jsonPath || p == key || strings.TrimPrefix(p, "$.") == strings.TrimPrefix(jsonPath, "$.") {
			return true
		}
	}
	return false
}

func strconvQuote(s string) string {
	return `"` + s + `"`
}