feat(smart-app): implement complete mobile app MVP

- App.tsx: full navigation (Auth stack + Main tabs with 5 screens)
- Auth: LoginScreen, RegisterScreen, ForgotPasswordScreen
- HomeScreen: dashboard with IoT metrics, weather widget, alerts, quick actions, sensors
- MapScreen: interactive map with layer toggles (6 layers)
- MarketplaceScreen: categories (6), products (5), search
- ChatScreen: AI chat with quick prompts (4), bot responses
- ProfileScreen: user info, stats, menu (9 items), logout
- AlertsScreen: alert list with severity, acknowledge
- SensorsScreen: sensor list with type filters (6 types), search
- ZonesScreen: zone cards with stats
- SettingsScreen: language picker (FR/EN/ES/DE), privacy, about
- Stores: iotStore (sensors, zones, alerts), notificationStore, uiStore + i18n
- Hooks: useSensors, useAlerts, useNotifications, useLocation
- Components: Card, Button, LoadingSpinner, ErrorBoundary, Header
- Services: iotService, notificationService (with axios API client)
- Utils: formatters (temp, AQI, noise, dates), validators (email, password, IBAN)
- Theme: colors.ts with full design system (Blue Ocean palette)
- Ditto: fixed MongoDB connection, new JWT secrets, official gateway image

smart-app-city/frontend/node_modules/js-yaml/lib/dumper.js

@@ -0,0 +1,937 @@
+'use strict'
+
+const common = require('./common')
+const YAMLException = require('./exception')
+const DEFAULT_SCHEMA = require('./schema/default')
+
+const _toString = Object.prototype.toString
+const _hasOwnProperty = Object.prototype.hasOwnProperty
+
+const CHAR_BOM = 0xFEFF
+const CHAR_TAB = 0x09 /* Tab */
+const CHAR_LINE_FEED = 0x0A /* LF */
+const CHAR_CARRIAGE_RETURN = 0x0D /* CR */
+const CHAR_SPACE = 0x20 /* Space */
+const CHAR_EXCLAMATION = 0x21 /* ! */
+const CHAR_DOUBLE_QUOTE = 0x22 /* " */
+const CHAR_SHARP = 0x23 /* # */
+const CHAR_PERCENT = 0x25 /* % */
+const CHAR_AMPERSAND = 0x26 /* & */
+const CHAR_SINGLE_QUOTE = 0x27 /* ' */
+const CHAR_ASTERISK = 0x2A /* * */
+const CHAR_COMMA = 0x2C /* , */
+const CHAR_MINUS = 0x2D /* - */
+const CHAR_COLON = 0x3A /* : */
+const CHAR_EQUALS = 0x3D /* = */
+const CHAR_GREATER_THAN = 0x3E /* > */
+const CHAR_QUESTION = 0x3F /* ? */
+const CHAR_COMMERCIAL_AT = 0x40 /* @ */
+const CHAR_LEFT_SQUARE_BRACKET = 0x5B /* [ */
+const CHAR_RIGHT_SQUARE_BRACKET = 0x5D /* ] */
+const CHAR_GRAVE_ACCENT = 0x60 /* ` */
+const CHAR_LEFT_CURLY_BRACKET = 0x7B /* { */
+const CHAR_VERTICAL_LINE = 0x7C /* | */
+const CHAR_RIGHT_CURLY_BRACKET = 0x7D /* } */
+
+const ESCAPE_SEQUENCES = {}
+
+ESCAPE_SEQUENCES[0x00] = '\\0'
+ESCAPE_SEQUENCES[0x07] = '\\a'
+ESCAPE_SEQUENCES[0x08] = '\\b'
+ESCAPE_SEQUENCES[0x09] = '\\t'
+ESCAPE_SEQUENCES[0x0A] = '\\n'
+ESCAPE_SEQUENCES[0x0B] = '\\v'
+ESCAPE_SEQUENCES[0x0C] = '\\f'
+ESCAPE_SEQUENCES[0x0D] = '\\r'
+ESCAPE_SEQUENCES[0x1B] = '\\e'
+ESCAPE_SEQUENCES[0x22] = '\\"'
+ESCAPE_SEQUENCES[0x5C] = '\\\\'
+ESCAPE_SEQUENCES[0x85] = '\\N'
+ESCAPE_SEQUENCES[0xA0] = '\\_'
+ESCAPE_SEQUENCES[0x2028] = '\\L'
+ESCAPE_SEQUENCES[0x2029] = '\\P'
+
+const DEPRECATED_BOOLEANS_SYNTAX = [
+  'y', 'Y', 'yes', 'Yes', 'YES', 'on', 'On', 'ON',
+  'n', 'N', 'no', 'No', 'NO', 'off', 'Off', 'OFF'
+]
+
+const DEPRECATED_BASE60_SYNTAX = /^[-+]?[0-9_]+(?::[0-9_]+)+(?:\.[0-9_]*)?$/
+
+function compileStyleMap (schema, map) {
+  if (map === null) return {}
+
+  const result = {}
+  const keys = Object.keys(map)
+
+  for (let index = 0, length = keys.length; index < length; index += 1) {
+    let tag = keys[index]
+    let style = String(map[tag])
+
+    if (tag.slice(0, 2) === '!!') {
+      tag = 'tag:yaml.org,2002:' + tag.slice(2)
+    }
+    const type = schema.compiledTypeMap['fallback'][tag]
+
+    if (type && _hasOwnProperty.call(type.styleAliases, style)) {
+      style = type.styleAliases[style]
+    }
+
+    result[tag] = style
+  }
+
+  return result
+}
+
+function encodeHex (character) {
+  let handle
+  let length
+
+  const string = character.toString(16).toUpperCase()
+
+  if (character <= 0xFF) {
+    handle = 'x'
+    length = 2
+  } else if (character <= 0xFFFF) {
+    handle = 'u'
+    length = 4
+  } else if (character <= 0xFFFFFFFF) {
+    handle = 'U'
+    length = 8
+  } else {
+    throw new YAMLException('code point within a string may not be greater than 0xFFFFFFFF')
+  }
+
+  return '\\' + handle + common.repeat('0', length - string.length) + string
+}
+
+const QUOTING_TYPE_SINGLE = 1
+const QUOTING_TYPE_DOUBLE = 2
+
+function State (options) {
+  this.schema = options['schema'] || DEFAULT_SCHEMA
+  this.indent = Math.max(1, (options['indent'] || 2))
+  this.noArrayIndent = options['noArrayIndent'] || false
+  this.skipInvalid = options['skipInvalid'] || false
+  this.flowLevel = (common.isNothing(options['flowLevel']) ? -1 : options['flowLevel'])
+  this.styleMap = compileStyleMap(this.schema, options['styles'] || null)
+  this.sortKeys = options['sortKeys'] || false
+  this.lineWidth = options['lineWidth'] || 80
+  this.noRefs = options['noRefs'] || false
+  this.noCompatMode = options['noCompatMode'] || false
+  this.condenseFlow = options['condenseFlow'] || false
+  this.quotingType = options['quotingType'] === '"' ? QUOTING_TYPE_DOUBLE : QUOTING_TYPE_SINGLE
+  this.forceQuotes = options['forceQuotes'] || false
+  this.replacer = typeof options['replacer'] === 'function' ? options['replacer'] : null
+
+  this.implicitTypes = this.schema.compiledImplicit
+  this.explicitTypes = this.schema.compiledExplicit
+
+  this.tag = null
+  this.result = ''
+
+  this.duplicates = []
+  this.usedDuplicates = null
+}
+
+// Indents every line in a string. Empty lines (\n only) are not indented.
+function indentString (string, spaces) {
+  const ind = common.repeat(' ', spaces)
+  let position = 0
+  let result = ''
+  const length = string.length
+
+  while (position < length) {
+    let line
+    const next = string.indexOf('\n', position)
+    if (next === -1) {
+      line = string.slice(position)
+      position = length
+    } else {
+      line = string.slice(position, next + 1)
+      position = next + 1
+    }
+
+    if (line.length && line !== '\n') result += ind
+
+    result += line
+  }
+
+  return result
+}
+
+function generateNextLine (state, level) {
+  return '\n' + common.repeat(' ', state.indent * level)
+}
+
+function testImplicitResolving (state, str) {
+  for (let index = 0, length = state.implicitTypes.length; index < length; index += 1) {
+    const type = state.implicitTypes[index]
+
+    if (type.resolve(str)) {
+      return true
+    }
+  }
+
+  return false
+}
+
+// [33] s-white ::= s-space | s-tab
+function isWhitespace (c) {
+  return c === CHAR_SPACE || c === CHAR_TAB
+}
+
+// Returns true if the character can be printed without escaping.
+// From YAML 1.2: "any allowed characters known to be non-printable
+// should also be escaped. [However,] This isn’t mandatory"
+// Derived from nb-char - \t - #x85 - #xA0 - #x2028 - #x2029.
+function isPrintable (c) {
+  return (c >= 0x00020 && c <= 0x00007E) ||
+    ((c >= 0x000A1 && c <= 0x00D7FF) && c !== 0x2028 && c !== 0x2029) ||
+    ((c >= 0x0E000 && c <= 0x00FFFD) && c !== CHAR_BOM) ||
+    (c >= 0x10000 && c <= 0x10FFFF)
+}
+
+// [34] ns-char ::= nb-char - s-white
+// [27] nb-char ::= c-printable - b-char - c-byte-order-mark
+// [26] b-char  ::= b-line-feed | b-carriage-return
+// Including s-white (for some reason, examples doesn't match specs in this aspect)
+// ns-char ::= c-printable - b-line-feed - b-carriage-return - c-byte-order-mark
+function isNsCharOrWhitespace (c) {
+  return isPrintable(c) &&
+    c !== CHAR_BOM &&
+    // - b-char
+    c !== CHAR_CARRIAGE_RETURN &&
+    c !== CHAR_LINE_FEED
+}
+
+// [127]  ns-plain-safe(c) ::= c = flow-out  ⇒ ns-plain-safe-out
+//                             c = flow-in   ⇒ ns-plain-safe-in
+//                             c = block-key ⇒ ns-plain-safe-out
+//                             c = flow-key  ⇒ ns-plain-safe-in
+// [128] ns-plain-safe-out ::= ns-char
+// [129]  ns-plain-safe-in ::= ns-char - c-flow-indicator
+// [130]  ns-plain-char(c) ::=  ( ns-plain-safe(c) - “:” - “#” )
+//                            | ( /* An ns-char preceding */ “#” )
+//                            | ( “:” /* Followed by an ns-plain-safe(c) */ )
+function isPlainSafe (c, prev, inblock) {
+  const cIsNsCharOrWhitespace = isNsCharOrWhitespace(c)
+  const cIsNsChar = cIsNsCharOrWhitespace && !isWhitespace(c)
+  return (
+    (
+      // ns-plain-safe
+      inblock // c = flow-in
+        ? cIsNsCharOrWhitespace
+        : cIsNsCharOrWhitespace &&
+          // - c-flow-indicator
+          c !== CHAR_COMMA &&
+          c !== CHAR_LEFT_SQUARE_BRACKET &&
+          c !== CHAR_RIGHT_SQUARE_BRACKET &&
+          c !== CHAR_LEFT_CURLY_BRACKET &&
+          c !== CHAR_RIGHT_CURLY_BRACKET
+    ) &&
+    // ns-plain-char
+    c !== CHAR_SHARP && // false on '#'
+    !(prev === CHAR_COLON && !cIsNsChar)
+  ) || // false on ': '
+  (isNsCharOrWhitespace(prev) && !isWhitespace(prev) && c === CHAR_SHARP) || // change to true on '[^ ]#'
+  (prev === CHAR_COLON && cIsNsChar) // change to true on ':[^ ]'
+}
+
+// Simplified test for values allowed as the first character in plain style.
+function isPlainSafeFirst (c) {
+  // Uses a subset of ns-char - c-indicator
+  // where ns-char = nb-char - s-white.
+  // No support of ( ( “?” | “:” | “-” ) /* Followed by an ns-plain-safe(c)) */ ) part
+  return isPrintable(c) &&
+    c !== CHAR_BOM &&
+    !isWhitespace(c) && // - s-white
+    // - (c-indicator ::=
+    // “-” | “?” | “:” | “,” | “[” | “]” | “{” | “}”
+    c !== CHAR_MINUS &&
+    c !== CHAR_QUESTION &&
+    c !== CHAR_COLON &&
+    c !== CHAR_COMMA &&
+    c !== CHAR_LEFT_SQUARE_BRACKET &&
+    c !== CHAR_RIGHT_SQUARE_BRACKET &&
+    c !== CHAR_LEFT_CURLY_BRACKET &&
+    c !== CHAR_RIGHT_CURLY_BRACKET &&
+    // | “#” | “&” | “*” | “!” | “|” | “=” | “>” | “'” | “"”
+    c !== CHAR_SHARP &&
+    c !== CHAR_AMPERSAND &&
+    c !== CHAR_ASTERISK &&
+    c !== CHAR_EXCLAMATION &&
+    c !== CHAR_VERTICAL_LINE &&
+    c !== CHAR_EQUALS &&
+    c !== CHAR_GREATER_THAN &&
+    c !== CHAR_SINGLE_QUOTE &&
+    c !== CHAR_DOUBLE_QUOTE &&
+    // | “%” | “@” | “`”)
+    c !== CHAR_PERCENT &&
+    c !== CHAR_COMMERCIAL_AT &&
+    c !== CHAR_GRAVE_ACCENT
+}
+
+// Simplified test for values allowed as the last character in plain style.
+function isPlainSafeLast (c) {
+  // just not whitespace or colon, it will be checked to be plain character later
+  return !isWhitespace(c) && c !== CHAR_COLON
+}
+
+// Same as 'string'.codePointAt(pos), but works in older browsers.
+function codePointAt (string, pos) {
+  const first = string.charCodeAt(pos)
+  let second
+
+  if (first >= 0xD800 && first <= 0xDBFF && pos + 1 < string.length) {
+    second = string.charCodeAt(pos + 1)
+    if (second >= 0xDC00 && second <= 0xDFFF) {
+      // https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
+      return (first - 0xD800) * 0x400 + second - 0xDC00 + 0x10000
+    }
+  }
+  return first
+}
+
+// Determines whether block indentation indicator is required.
+function needIndentIndicator (string) {
+  const leadingSpaceRe = /^\n* /
+  return leadingSpaceRe.test(string)
+}
+
+const STYLE_PLAIN = 1
+const STYLE_SINGLE = 2
+const STYLE_LITERAL = 3
+const STYLE_FOLDED = 4
+const STYLE_DOUBLE = 5
+
+// Determines which scalar styles are possible and returns the preferred style.
+// lineWidth = -1 => no limit.
+// Pre-conditions: str.length > 0.
+// Post-conditions:
+//    STYLE_PLAIN or STYLE_SINGLE => no \n are in the string.
+//    STYLE_LITERAL => no lines are suitable for folding (or lineWidth is -1).
+//    STYLE_FOLDED => a line > lineWidth and can be folded (and lineWidth != -1).
+function chooseScalarStyle (string, singleLineOnly, indentPerLevel, lineWidth,
+  testAmbiguousType, quotingType, forceQuotes, inblock) {
+  let i
+  let char = 0
+  let prevChar = null
+  let hasLineBreak = false
+  let hasFoldableLine = false // only checked if shouldTrackWidth
+  const shouldTrackWidth = lineWidth !== -1
+  let previousLineBreak = -1 // count the first line correctly
+  let plain = isPlainSafeFirst(codePointAt(string, 0)) &&
+    isPlainSafeLast(codePointAt(string, string.length - 1))
+
+  if (singleLineOnly || forceQuotes) {
+    // Case: no block styles.
+    // Check for disallowed characters to rule out plain and single.
+    for (i = 0; i < string.length; char >= 0x10000 ? i += 2 : i++) {
+      char = codePointAt(string, i)
+      if (!isPrintable(char)) {
+        return STYLE_DOUBLE
+      }
+      plain = plain && isPlainSafe(char, prevChar, inblock)
+      prevChar = char
+    }
+  } else {
+    // Case: block styles permitted.
+    for (i = 0; i < string.length; char >= 0x10000 ? i += 2 : i++) {
+      char = codePointAt(string, i)
+      if (char === CHAR_LINE_FEED) {
+        hasLineBreak = true
+        // Check if any line can be folded.
+        if (shouldTrackWidth) {
+          hasFoldableLine = hasFoldableLine ||
+            // Foldable line = too long, and not more-indented.
+            (i - previousLineBreak - 1 > lineWidth &&
+             string[previousLineBreak + 1] !== ' ')
+          previousLineBreak = i
+        }
+      } else if (!isPrintable(char)) {
+        return STYLE_DOUBLE
+      }
+      plain = plain && isPlainSafe(char, prevChar, inblock)
+      prevChar = char
+    }
+    // in case the end is missing a \n
+    hasFoldableLine = hasFoldableLine || (shouldTrackWidth &&
+      (i - previousLineBreak - 1 > lineWidth &&
+       string[previousLineBreak + 1] !== ' '))
+  }
+  // Although every style can represent \n without escaping, prefer block styles
+  // for multiline, since they're more readable and they don't add empty lines.
+  // Also prefer folding a super-long line.
+  if (!hasLineBreak && !hasFoldableLine) {
+    // Strings interpretable as another type have to be quoted;
+    // e.g. the string 'true' vs. the boolean true.
+    if (plain && !forceQuotes && !testAmbiguousType(string)) {
+      return STYLE_PLAIN
+    }
+    return quotingType === QUOTING_TYPE_DOUBLE ? STYLE_DOUBLE : STYLE_SINGLE
+  }
+  // Edge case: block indentation indicator can only have one digit.
+  if (indentPerLevel > 9 && needIndentIndicator(string)) {
+    return STYLE_DOUBLE
+  }
+  // At this point we know block styles are valid.
+  // Prefer literal style unless we want to fold.
+  if (!forceQuotes) {
+    return hasFoldableLine ? STYLE_FOLDED : STYLE_LITERAL
+  }
+  return quotingType === QUOTING_TYPE_DOUBLE ? STYLE_DOUBLE : STYLE_SINGLE
+}
+
+// Note: line breaking/folding is implemented for only the folded style.
+// NB. We drop the last trailing newline (if any) of a returned block scalar
+//  since the dumper adds its own newline. This always works:
+//    • No ending newline => unaffected; already using strip "-" chomping.
+//    • Ending newline    => removed then restored.
+//  Importantly, this keeps the "+" chomp indicator from gaining an extra line.
+function writeScalar (state, string, level, iskey, inblock) {
+  state.dump = (function () {
+    if (string.length === 0) {
+      return state.quotingType === QUOTING_TYPE_DOUBLE ? '""' : "''"
+    }
+    if (!state.noCompatMode) {
+      if (DEPRECATED_BOOLEANS_SYNTAX.indexOf(string) !== -1 || DEPRECATED_BASE60_SYNTAX.test(string)) {
+        return state.quotingType === QUOTING_TYPE_DOUBLE ? ('"' + string + '"') : ("'" + string + "'")
+      }
+    }
+
+    const indent = state.indent * Math.max(1, level) // no 0-indent scalars
+    // As indentation gets deeper, let the width decrease monotonically
+    // to the lower bound min(state.lineWidth, 40).
+    // Note that this implies
+    //  state.lineWidth ≤ 40 + state.indent: width is fixed at the lower bound.
+    //  state.lineWidth > 40 + state.indent: width decreases until the lower bound.
+    // This behaves better than a constant minimum width which disallows narrower options,
+    // or an indent threshold which causes the width to suddenly increase.
+    const lineWidth = (state.lineWidth === -1)
+      ? -1
+      : Math.max(Math.min(state.lineWidth, 40), state.lineWidth - indent)
+
+    // Without knowing if keys are implicit/explicit, assume implicit for safety.
+    const singleLineOnly = iskey ||
+      // No block styles in flow mode.
+      (state.flowLevel > -1 && level >= state.flowLevel)
+    function testAmbiguity (string) {
+      return testImplicitResolving(state, string)
+    }
+
+    switch (chooseScalarStyle(string, singleLineOnly, state.indent, lineWidth,
+      testAmbiguity, state.quotingType, state.forceQuotes && !iskey, inblock)) {
+      case STYLE_PLAIN:
+        return string
+      case STYLE_SINGLE:
+        return "'" + string.replace(/'/g, "''") + "'"
+      case STYLE_LITERAL:
+        return '|' + blockHeader(string, state.indent) +
+          dropEndingNewline(indentString(string, indent))
+      case STYLE_FOLDED:
+        return '>' + blockHeader(string, state.indent) +
+          dropEndingNewline(indentString(foldString(string, lineWidth), indent))
+      case STYLE_DOUBLE:
+        return '"' + escapeString(string, lineWidth) + '"'
+      default:
+        throw new YAMLException('impossible error: invalid scalar style')
+    }
+  }())
+}
+
+// Pre-conditions: string is valid for a block scalar, 1 <= indentPerLevel <= 9.
+function blockHeader (string, indentPerLevel) {
+  const indentIndicator = needIndentIndicator(string) ? String(indentPerLevel) : ''
+
+  // note the special case: the string '\n' counts as a "trailing" empty line.
+  const clip = string[string.length - 1] === '\n'
+  const keep = clip && (string[string.length - 2] === '\n' || string === '\n')
+  const chomp = keep ? '+' : (clip ? '' : '-')
+
+  return indentIndicator + chomp + '\n'
+}
+
+// (See the note for writeScalar.)
+function dropEndingNewline (string) {
+  return string[string.length - 1] === '\n' ? string.slice(0, -1) : string
+}
+
+// Note: a long line without a suitable break point will exceed the width limit.
+// Pre-conditions: every char in str isPrintable, str.length > 0, width > 0.
+function foldString (string, width) {
+  // In folded style, $k$ consecutive newlines output as $k+1$ newlines—
+  // unless they're before or after a more-indented line, or at the very
+  // beginning or end, in which case $k$ maps to $k$.
+  // Therefore, parse each chunk as newline(s) followed by a content line.
+  const lineRe = /(\n+)([^\n]*)/g
+
+  // first line (possibly an empty line)
+  let result = (function () {
+    let nextLF = string.indexOf('\n')
+    nextLF = nextLF !== -1 ? nextLF : string.length
+    lineRe.lastIndex = nextLF
+    return foldLine(string.slice(0, nextLF), width)
+  }())
+  // If we haven't reached the first content line yet, don't add an extra \n.
+  let prevMoreIndented = string[0] === '\n' || string[0] === ' '
+  let moreIndented
+
+  // rest of the lines
+  let match
+  while ((match = lineRe.exec(string))) {
+    const prefix = match[1]
+    const line = match[2]
+
+    moreIndented = (line[0] === ' ')
+    result += prefix +
+      ((!prevMoreIndented && !moreIndented && line !== '') ? '\n' : '') +
+      foldLine(line, width)
+    prevMoreIndented = moreIndented
+  }
+
+  return result
+}
+
+// Greedy line breaking.
+// Picks the longest line under the limit each time,
+// otherwise settles for the shortest line over the limit.
+// NB. More-indented lines *cannot* be folded, as that would add an extra \n.
+function foldLine (line, width) {
+  if (line === '' || line[0] === ' ') return line
+
+  // Since a more-indented line adds a \n, breaks can't be followed by a space.
+  const breakRe = / [^ ]/g // note: the match index will always be <= length-2.
+  let match
+  // start is an inclusive index. end, curr, and next are exclusive.
+  let start = 0
+  let end
+  let curr = 0
+  let next = 0
+  let result = ''
+
+  // Invariants: 0 <= start <= length-1.
+  //   0 <= curr <= next <= max(0, length-2). curr - start <= width.
+  // Inside the loop:
+  //   A match implies length >= 2, so curr and next are <= length-2.
+  while ((match = breakRe.exec(line))) {
+    next = match.index
+    // maintain invariant: curr - start <= width
+    if (next - start > width) {
+      end = (curr > start) ? curr : next // derive end <= length-2
+      result += '\n' + line.slice(start, end)
+      // skip the space that was output as \n
+      start = end + 1                    // derive start <= length-1
+    }
+    curr = next
+  }
+
+  // By the invariants, start <= length-1, so there is something left over.
+  // It is either the whole string or a part starting from non-whitespace.
+  result += '\n'
+  // Insert a break if the remainder is too long and there is a break available.
+  if (line.length - start > width && curr > start) {
+    result += line.slice(start, curr) + '\n' + line.slice(curr + 1)
+  } else {
+    result += line.slice(start)
+  }
+
+  return result.slice(1) // drop extra \n joiner
+}
+
+// Escapes a double-quoted string.
+function escapeString (string) {
+  let result = ''
+  let char = 0
+
+  for (let i = 0; i < string.length; char >= 0x10000 ? i += 2 : i++) {
+    char = codePointAt(string, i)
+    const escapeSeq = ESCAPE_SEQUENCES[char]
+
+    if (!escapeSeq && isPrintable(char)) {
+      result += string[i]
+      if (char >= 0x10000) result += string[i + 1]
+    } else {
+      result += escapeSeq || encodeHex(char)
+    }
+  }
+
+  return result
+}
+
+function writeFlowSequence (state, level, object) {
+  let _result = ''
+  const _tag = state.tag
+
+  for (let index = 0, length = object.length; index < length; index += 1) {
+    let value = object[index]
+
+    if (state.replacer) {
+      value = state.replacer.call(object, String(index), value)
+    }
+
+    // Write only valid elements, put null instead of invalid elements.
+    if (writeNode(state, level, value, false, false) ||
+        (typeof value === 'undefined' &&
+         writeNode(state, level, null, false, false))) {
+      if (_result !== '') _result += ',' + (!state.condenseFlow ? ' ' : '')
+      _result += state.dump
+    }
+  }
+
+  state.tag = _tag
+  state.dump = '[' + _result + ']'
+}
+
+function writeBlockSequence (state, level, object, compact) {
+  let _result = ''
+  const _tag = state.tag
+
+  for (let index = 0, length = object.length; index < length; index += 1) {
+    let value = object[index]
+
+    if (state.replacer) {
+      value = state.replacer.call(object, String(index), value)
+    }
+
+    // Write only valid elements, put null instead of invalid elements.
+    if (writeNode(state, level + 1, value, true, true, false, true) ||
+        (typeof value === 'undefined' &&
+         writeNode(state, level + 1, null, true, true, false, true))) {
+      if (!compact || _result !== '') {
+        _result += generateNextLine(state, level)
+      }
+
+      if (state.dump && CHAR_LINE_FEED === state.dump.charCodeAt(0)) {
+        _result += '-'
+      } else {
+        _result += '- '
+      }
+
+      _result += state.dump
+    }
+  }
+
+  state.tag = _tag
+  state.dump = _result || '[]' // Empty sequence if no valid values.
+}
+
+function writeFlowMapping (state, level, object) {
+  let _result = ''
+  const _tag = state.tag
+  const objectKeyList = Object.keys(object)
+
+  for (let index = 0, length = objectKeyList.length; index < length; index += 1) {
+    let pairBuffer = ''
+    if (_result !== '') pairBuffer += ', '
+
+    if (state.condenseFlow) pairBuffer += '"'
+
+    const objectKey = objectKeyList[index]
+    let objectValue = object[objectKey]
+
+    if (state.replacer) {
+      objectValue = state.replacer.call(object, objectKey, objectValue)
+    }
+
+    if (!writeNode(state, level, objectKey, false, false)) {
+      continue // Skip this pair because of invalid key;
+    }
+
+    if (state.dump.length > 1024) pairBuffer += '? '
+
+    pairBuffer += state.dump + (state.condenseFlow ? '"' : '') + ':' + (state.condenseFlow ? '' : ' ')
+
+    if (!writeNode(state, level, objectValue, false, false)) {
+      continue // Skip this pair because of invalid value.
+    }
+
+    pairBuffer += state.dump
+
+    // Both key and value are valid.
+    _result += pairBuffer
+  }
+
+  state.tag = _tag
+  state.dump = '{' + _result + '}'
+}
+
+function writeBlockMapping (state, level, object, compact) {
+  let _result = ''
+  const _tag = state.tag
+  const objectKeyList = Object.keys(object)
+
+  // Allow sorting keys so that the output file is deterministic
+  if (state.sortKeys === true) {
+    // Default sorting
+    objectKeyList.sort()
+  } else if (typeof state.sortKeys === 'function') {
+    // Custom sort function
+    objectKeyList.sort(state.sortKeys)
+  } else if (state.sortKeys) {
+    // Something is wrong
+    throw new YAMLException('sortKeys must be a boolean or a function')
+  }
+
+  for (let index = 0, length = objectKeyList.length; index < length; index += 1) {
+    let pairBuffer = ''
+
+    if (!compact || _result !== '') {
+      pairBuffer += generateNextLine(state, level)
+    }
+
+    const objectKey = objectKeyList[index]
+    let objectValue = object[objectKey]
+
+    if (state.replacer) {
+      objectValue = state.replacer.call(object, objectKey, objectValue)
+    }
+
+    if (!writeNode(state, level + 1, objectKey, true, true, true)) {
+      continue // Skip this pair because of invalid key.
+    }
+
+    const explicitPair = (state.tag !== null && state.tag !== '?') ||
+                   (state.dump && state.dump.length > 1024)
+
+    if (explicitPair) {
+      if (state.dump && CHAR_LINE_FEED === state.dump.charCodeAt(0)) {
+        pairBuffer += '?'
+      } else {
+        pairBuffer += '? '
+      }
+    }
+
+    pairBuffer += state.dump
+
+    if (explicitPair) {
+      pairBuffer += generateNextLine(state, level)
+    }
+
+    if (!writeNode(state, level + 1, objectValue, true, explicitPair)) {
+      continue // Skip this pair because of invalid value.
+    }
+
+    if (state.dump && CHAR_LINE_FEED === state.dump.charCodeAt(0)) {
+      pairBuffer += ':'
+    } else {
+      pairBuffer += ': '
+    }
+
+    pairBuffer += state.dump
+
+    // Both key and value are valid.
+    _result += pairBuffer
+  }
+
+  state.tag = _tag
+  state.dump = _result || '{}' // Empty mapping if no valid pairs.
+}
+
+function detectType (state, object, explicit) {
+  const typeList = explicit ? state.explicitTypes : state.implicitTypes
+
+  for (let index = 0, length = typeList.length; index < length; index += 1) {
+    const type = typeList[index]
+
+    if ((type.instanceOf || type.predicate) &&
+        (!type.instanceOf || ((typeof object === 'object') && (object instanceof type.instanceOf))) &&
+        (!type.predicate || type.predicate(object))) {
+      if (explicit) {
+        if (type.multi && type.representName) {
+          state.tag = type.representName(object)
+        } else {
+          state.tag = type.tag
+        }
+      } else {
+        state.tag = '?'
+      }
+
+      if (type.represent) {
+        const style = state.styleMap[type.tag] || type.defaultStyle
+
+        let _result
+        if (_toString.call(type.represent) === '[object Function]') {
+          _result = type.represent(object, style)
+        } else if (_hasOwnProperty.call(type.represent, style)) {
+          _result = type.represent[style](object, style)
+        } else {
+          throw new YAMLException('!<' + type.tag + '> tag resolver accepts not "' + style + '" style')
+        }
+
+        state.dump = _result
+      }
+
+      return true
+    }
+  }
+
+  return false
+}
+
+// Serializes `object` and writes it to global `result`.
+// Returns true on success, or false on invalid object.
+//
+function writeNode (state, level, object, block, compact, iskey, isblockseq) {
+  state.tag = null
+  state.dump = object
+
+  if (!detectType(state, object, false)) {
+    detectType(state, object, true)
+  }
+
+  const type = _toString.call(state.dump)
+  const inblock = block
+
+  if (block) {
+    block = (state.flowLevel < 0 || state.flowLevel > level)
+  }
+
+  const objectOrArray = type === '[object Object]' || type === '[object Array]'
+  let duplicateIndex
+  let duplicate
+
+  if (objectOrArray) {
+    duplicateIndex = state.duplicates.indexOf(object)
+    duplicate = duplicateIndex !== -1
+  }
+
+  if ((state.tag !== null && state.tag !== '?') || duplicate || (state.indent !== 2 && level > 0)) {
+    compact = false
+  }
+
+  if (duplicate && state.usedDuplicates[duplicateIndex]) {
+    state.dump = '*ref_' + duplicateIndex
+  } else {
+    if (objectOrArray && duplicate && !state.usedDuplicates[duplicateIndex]) {
+      state.usedDuplicates[duplicateIndex] = true
+    }
+    if (type === '[object Object]') {
+      if (block && (Object.keys(state.dump).length !== 0)) {
+        writeBlockMapping(state, level, state.dump, compact)
+        if (duplicate) {
+          state.dump = '&ref_' + duplicateIndex + state.dump
+        }
+      } else {
+        writeFlowMapping(state, level, state.dump)
+        if (duplicate) {
+          state.dump = '&ref_' + duplicateIndex + ' ' + state.dump
+        }
+      }
+    } else if (type === '[object Array]') {
+      if (block && (state.dump.length !== 0)) {
+        if (state.noArrayIndent && !isblockseq && level > 0) {
+          writeBlockSequence(state, level - 1, state.dump, compact)
+        } else {
+          writeBlockSequence(state, level, state.dump, compact)
+        }
+        if (duplicate) {
+          state.dump = '&ref_' + duplicateIndex + state.dump
+        }
+      } else {
+        writeFlowSequence(state, level, state.dump)
+        if (duplicate) {
+          state.dump = '&ref_' + duplicateIndex + ' ' + state.dump
+        }
+      }
+    } else if (type === '[object String]') {
+      if (state.tag !== '?') {
+        writeScalar(state, state.dump, level, iskey, inblock)
+      }
+    } else if (type === '[object Undefined]') {
+      return false
+    } else {
+      if (state.skipInvalid) return false
+      throw new YAMLException('unacceptable kind of an object to dump ' + type)
+    }
+
+    if (state.tag !== null && state.tag !== '?') {
+      // Need to encode all characters except those allowed by the spec:
+      //
+      // [35] ns-dec-digit    ::=  [#x30-#x39] /* 0-9 */
+      // [36] ns-hex-digit    ::=  ns-dec-digit
+      //                         | [#x41-#x46] /* A-F */ | [#x61-#x66] /* a-f */
+      // [37] ns-ascii-letter ::=  [#x41-#x5A] /* A-Z */ | [#x61-#x7A] /* a-z */
+      // [38] ns-word-char    ::=  ns-dec-digit | ns-ascii-letter | “-”
+      // [39] ns-uri-char     ::=  “%” ns-hex-digit ns-hex-digit | ns-word-char | “#”
+      //                         | “;” | “/” | “?” | “:” | “@” | “&” | “=” | “+” | “$” | “,”
+      //                         | “_” | “.” | “!” | “~” | “*” | “'” | “(” | “)” | “[” | “]”
+      //
+      // Also need to encode '!' because it has special meaning (end of tag prefix).
+      //
+      let tagStr = encodeURI(
+        state.tag[0] === '!' ? state.tag.slice(1) : state.tag
+      ).replace(/!/g, '%21')
+
+      if (state.tag[0] === '!') {
+        tagStr = '!' + tagStr
+      } else if (tagStr.slice(0, 18) === 'tag:yaml.org,2002:') {
+        tagStr = '!!' + tagStr.slice(18)
+      } else {
+        tagStr = '!<' + tagStr + '>'
+      }
+
+      state.dump = tagStr + ' ' + state.dump
+    }
+  }
+
+  return true
+}
+
+function getDuplicateReferences (object, state) {
+  const objects = []
+  const duplicatesIndexes = []
+
+  inspectNode(object, objects, duplicatesIndexes)
+
+  const length = duplicatesIndexes.length
+  for (let index = 0; index < length; index += 1) {
+    state.duplicates.push(objects[duplicatesIndexes[index]])
+  }
+  state.usedDuplicates = new Array(length)
+}
+
+function inspectNode (object, objects, duplicatesIndexes) {
+  if (object !== null && typeof object === 'object') {
+    const index = objects.indexOf(object)
+    if (index !== -1) {
+      if (duplicatesIndexes.indexOf(index) === -1) {
+        duplicatesIndexes.push(index)
+      }
+    } else {
+      objects.push(object)
+
+      if (Array.isArray(object)) {
+        for (let i = 0, length = object.length; i < length; i += 1) {
+          inspectNode(object[i], objects, duplicatesIndexes)
+        }
+      } else {
+        const objectKeyList = Object.keys(object)
+
+        for (let i = 0, length = objectKeyList.length; i < length; i += 1) {
+          inspectNode(object[objectKeyList[i]], objects, duplicatesIndexes)
+        }
+      }
+    }
+  }
+}
+
+function dump (input, options) {
+  options = options || {}
+
+  const state = new State(options)
+
+  if (!state.noRefs) getDuplicateReferences(input, state)
+
+  let value = input
+
+  if (state.replacer) {
+    value = state.replacer.call({ '': value }, '', value)
+  }
+
+  if (writeNode(state, 0, value, true, true)) return state.dump + '\n'
+
+  return ''
+}
+
+module.exports.dump = dump