class RouterError extends Error {
  constructor(route1, route2, ...params) {
    // Pass remaining arguments (including vendor specific ones) to parent constructor
    super(...params);

    // Maintains proper stack trace for where our error was thrown (only available on V8)
    if (Error.captureStackTrace) {
      Error.captureStackTrace(this, RouterError);
    }

    this.name = "RouterError";
    this.routeA = route1
    this.routeB = route2
  }
}

function Child(split, x, i) {
  this.path = null
  this.isParams = split[x].isParams ? split[x].word : null
  this.isFullParams = split[x].isFullParams ? split[x].word : null
  this.paramVarName = split[x].paramVarName ?? null
  this.char = !this.isParams && !this.isFullParams ? split[x].word[i] || '/' : null
  this.count = 0
  this.children = []
}

function buildChild(x, i, splitPaths) {
  let splitPath = splitPaths[0]
  let letter = new Child(splitPath.split, x, i)

  let consume = []
  if (splitPath.split.length === x + 1
      && (splitPath.split[x].isParams
          || splitPath.split[x].isFullParams
          || splitPath.split[x].word.length === i + 1)) {
    letter.path = splitPath.entry
    letter.count += 1
  } else {
    consume = [splitPath]
  }

  for (let y = 1; y < splitPaths.length; y++) {
    let checkPath = splitPaths[y]
    if (!checkPath.split[x]
        || checkPath.split[x].isParams !== splitPath.split[x].isParams
        || checkPath.split[x].isFullParams !== splitPath.split[x].isFullParams
        || !checkPath.split[x].isParams
            && !checkPath.split[x].isFullParams
            && (checkPath.split[x].word[i] || '/') !== letter.char) break
    consume.push(checkPath)
  }

  letter.count += consume.length
  if (splitPath.split[x].word.length === i || splitPath.split[x].isParams || splitPath.split[x].isFullParams) {
    x++
    i = -1
  }
  while (consume.length) {
    letter.children.push(buildChild(x, i + 1, consume))
    consume.splice(0, letter.children[letter.children.length - 1].count)
  }
  return letter
}

export function buildTree(splitPaths) {
  let builder = []
  while (splitPaths.length) {
    builder.push(buildChild(0, 0, splitPaths))
    splitPaths.splice(0, builder[builder.length - 1].count)
  }
  return builder
}

const regParamPrefix = /^::?/
const regCleanNonAschii = /(?![a-zA-Z_])./g
const regCleanRest = /_+/g

function splitAndSortPaths(paths, separateStatic = true) {
  let staticPaths = new Map()
  let paramsPaths = []
  let collator = new Intl.Collator('en', { sensitivity: 'accent' });

  paths.forEach(function(entry) {
    if (entry.path[0] !== '/') throw new RouterError(entry, null, 'Specified route was missing forward slash at start')

    // Collect static paths separately
    if (entry.path.indexOf('/:') < 0 && separateStatic) {
      return staticPaths.set(entry.path, {
        path: entry,
        params: {}
      })
    }

    // Collect params path separately
    paramsPaths.push({
      split: entry.path.slice(1).split(/\//g).map(function(word) {
        let actualWord = word.replace(regParamPrefix, '')
        return {
          word: actualWord,
          isParams: word[0] === ':' && word[1] !== ':',
          isFullParams: word[0] === ':' && word[1] === ':',
          paramVarName: word[0] === ':'
            ? actualWord.replace(regCleanNonAschii, '_').replace(regCleanRest, '_')
            : null
        }
      }),
      entry,
    })
  })

  paramsPaths.sort(function(aGroup, bGroup) {
    let length = Math.max(aGroup.split.length, bGroup.split.length)
    for (let x = 0; x < length; x++) {
      let a = aGroup.split[x]
      let b = bGroup.split[x]
      if (!a) return -1
      if (!b) return 1
      // Full params go last
      if (a.isFullParams && b.isFullParams) throw new RouterError(aGroup.entry, bGroup.entry, 'Two full path routes found on same level')
      if (a.isFullParams) return 1
      if (b.isFullParams) return -1
      // Params go second last
      if (a.isParams && !b.isParams) return 1
      if (!a.isParams && b.isParams) return -1
      // otherwise sort alphabetically if not identical
      if (a.word !== b.word) return collator.compare(a.word, b.word)
    }
    throw new RouterError(aGroup, bGroup, 'Two identical paths were found')
  })

  return {
    staticPaths,
    paramsPaths,
  }
}

const SlashCode = '/'.charCodeAt(0)

function getIndex(offset, additions, params) {
  return (offset + additions)
    + (params.length
        ? ' + ' + params.map(a => `offset${a[1]}`).join(' + ')
        : '')
}

function treeIntoCompiledCodeReturnPath(indentString, paths, branch, params, alt) {
  let pathIndex = paths.indexOf(branch.path)
  if (pathIndex < 0) {
    throw new RouterError(branch.path, null, 'InternalError: Specified path was not found in paths')
  }
  let output = ''
  output += '\n' + indentString + `return {`
  output += '\n' + indentString + `  path: paths[${pathIndex}],`
  if (params.length) {
    output += '\n' + indentString + `  params: {`
    for (let param of params) {
      if (alt === 0) {
        output += '\n' + indentString + `    ${param[0]}: s${param[1]}.toString(),`
      } else if (alt === 1 || alt === 3) {
        output += '\n' + indentString + `    ${param[0]}: s${param[1]},`
      } else if (alt === 2) {
        output += '\n' + indentString + `    ${param[0]}: textDecoder.decode(s${param[1]}),`
      }
    }
    output += '\n' + indentString + `  },`
  } else {
  output += '\n' + indentString + `  params: {},`
  }
  output += '\n' + indentString + `}`
  return output
}

function treeIntoCompiledCodeBranch(paths, branches, indent = 0, params = [], alt = 0) {
  let output = ''
  let indentation = ''.padStart((indent - params.length) * 2)
  let addEndBracket = true

  for (let i = 0; i < branches.length; i++) {
    let branch = branches[i]
    if (i > 0) {
      if (!branch.isParams && !branch.isFullParams) {
        output += ' else '
      } else {
        // output += '} //'
        output += '\n' + indentation
      }
    }

    if (!branch.isParams && !branch.isFullParams) {
      output += `if (buf[${getIndex(indent, 0, params)}] === ${branch.char.charCodeAt(0)}) { // ${branch.char}`

      if (branch.path) {
        output += '\n' + indentation + `  if (buf.length === ${getIndex(indent, 1, params)}) {`
        output += treeIntoCompiledCodeReturnPath(indentation + '    ', paths, branch, params, alt)
        output += '\n' + indentation + `  }`
      }
    } else {
      addEndBracket = false
      let paramVarName = (params.length + 1) + '_' + branch.paramVarName
      output += `let s${paramVarName} = str.slice(${getIndex(indent, 0, params)}${branch.isFullParams ? '' : `, buf.indexOf(${SlashCode}, ${getIndex(indent, 0, params)}) >>> 0`})`
      output += '\n' + indentation + `let offset${paramVarName} = s${paramVarName}.length`
      output += '\n' + indentation
      params.push([branch.isParams || branch.isFullParams, paramVarName])

      if (branch.isFullParams) {
        output += treeIntoCompiledCodeReturnPath(indentation, paths, branch, params, alt)
      } else if (branch.path) {
        output += '\n' + indentation + `if (buf.length === ${getIndex(indent, 0, params)}) {`
        output += treeIntoCompiledCodeReturnPath(indentation + '  ', paths, branch, params, alt)
        output += '\n' + indentation + `}`
      }
    }

    if (branch.children.length) {
      if (branch.path) {
        output += ' else '
      } else {
        output += '\n' + indentation + '  '
      }
      output += treeIntoCompiledCodeBranch(paths, branch.children, indent + 1, params.slice())
    }
    if (addEndBracket) {
      output += '\n' + indentation + '} '
    }
  }
  return output
}

export function treeIntoCompiledCode(paths, tree) {
  let output = 'return function RBufferStrSlice(paths, static, str) {'
  output += '\n  let checkStatic = static.get(str)'
  output += '\n  if(checkStatic) {'
  output += '\n    return checkStatic'
  output += '\n  }'
  output += '\n  var buf = Buffer.from(str)'
  output += '\n  ' + treeIntoCompiledCodeBranch(paths, tree, 1, [], 1)
  output += '\n  return null'
  output += '\n}'
  return new Function(output)()
}

export function compilePaths(paths) {
  let splitPaths = splitAndSortPaths(paths)
  let tree = buildTree(splitPaths.paramsPaths.slice())
  let compiled = treeIntoCompiledCode(paths, tree)
  return compiled.bind(null, paths, splitPaths.staticPaths)
}