/* -----------------------------------------------------------------------------
Copyright 2021 Kevin P. Barry

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
----------------------------------------------------------------------------- */

// Author: Kevin P. Barry [ta0kira@gmail.com]

define ParseChars {
  float (data) {
    Float total <- 0.0
    Float sign <- 0.0
    Bool hasDigit <- false
    Bool needExpDigits <- false

    optional Order<Char> curr <- data.defaultOrder()

    // Parse to the left of '.'.
    while (present(curr)) {
      Char c <- require(curr).get()
      curr <- require(curr).next()
      $ReadOnly[c]$
      $Hidden[curr]$
      if (sign == 0.0) {
        if (c == '-') {
          sign <- -1.0
          continue
        } elif (c == '+') {
          sign <- 1.0
          continue
        } else {
          sign <- 1.0
        }
      }
      if (c >= '0' && c <= '9') {
        hasDigit <- true
        total <- 10.0*total+(c.asInt() - '0'.asInt()).asFloat()
        continue
      }
      if (c == '.') {
        break
      }
      if (c == 'E' || c == 'e') {
        if (!hasDigit) {
          return autoFail<Float>(c)
        } else {
          needExpDigits <- true
          break
        }
      }
      return autoFail<Float>(c)
    }

    if (!needExpDigits) {

      Float decimal <- 0.1

      // Parse to the right of '.'.
      while (present(curr)) {
        Char c <- require(curr).get()
        curr <- require(curr).next()
        $ReadOnly[c]$
        $Hidden[curr]$
        if (c >= '0' && c <= '9') {
          hasDigit <- true
          total <- total+decimal*(c.asInt() - '0'.asInt()).asFloat()
          decimal <- decimal/10.0
          continue
        }
        if (c == 'E' || c == 'e') {
          if (!hasDigit) {
            return autoFail<Float>(c)
          } else {
            needExpDigits <- true
            break
          }
        }
        return autoFail<Float>(c)
      }

    }

    if (!hasDigit) {
      return ErrorOr:error("missing digits in Float value")
    }

    total <- sign*total
    $Hidden[sign, hasDigit]$

    Int expSign <- 0
    Int exp <- 0

    if (needExpDigits) {

      // Parse exponent.
      while (present(curr)) {
        Char c <- require(curr).get()
        curr <- require(curr).next()
        $ReadOnly[c]$
        $Hidden[curr, total]$
        if (expSign == 0) {
          if (c == '-') {
            expSign <- -1
            continue
          } elif (c == '+') {
            expSign <- 1
            continue
          } else {
            expSign <- 1
          }
        }
        if (c >= '0' && c <= '9') {
          needExpDigits <- false
          exp <- 10*exp+(c.asInt() - '0'.asInt())
          continue
        }
        return autoFail<Float>(c)
      }

    }

    if (needExpDigits) {
      return ErrorOr:error("missing digits in Float exponent")
    }

    traverse (Counter.zeroIndexed(exp) -> _) {
      if (expSign > 0) {
        total <- 10.0*total
      } else {
        total <- total/10.0
      }
    }

    return ErrorOr:value(total)
  }

  int (data) {
    Int total <- 0
    Int sign <- 0
    Bool hasDigit <- false

    traverse (data.defaultOrder() -> Char c) {
      if (sign == 0) {
        if (c == '-') {
          sign <- -1
          continue
        } elif (c == '+') {
          sign <- 1
          continue
        } else {
          sign <- 1
        }
      }
      if (c >= '0' && c <= '9') {
        hasDigit <- true
        total <- 10*total+(c.asInt() - '0'.asInt())
        continue
      }
      return autoFail<Int>(c)
    }

    if (!hasDigit) {
      return ErrorOr:error("missing digits in Int value")
    }

    return ErrorOr:value(sign*total)
  }

  hexInt (data) {
    Int total <- 0
    Int sign <- 0
    Bool hasDigit <- false

    traverse (data.defaultOrder() -> Char c) {
      if (sign == 0) {
        if (c == '-') {
          sign <- -1
          continue
        } elif (c == '+') {
          sign <- 1
          continue
        } else {
          sign <- 1
        }
      }
      if (c >= '0' && c <= '9') {
        hasDigit <- true
        total <- 16*total+(c.asInt() - '0'.asInt())
        continue
      }
      if (c >= 'a' && c <= 'f') {
        hasDigit <- true
        total <- 16*total+(c.asInt() - 'a'.asInt() + 10)
        continue
      }
      if (c >= 'A' && c <= 'F') {
        hasDigit <- true
        total <- 16*total+(c.asInt() - 'A'.asInt() + 10)
        continue
      }
      return autoFail<Int>(c)
    }

    if (!hasDigit) {
      return ErrorOr:error("missing digits in Int value")
    }

    return ErrorOr:value(sign*total)
  }

  octInt (data) {
    Int total <- 0
    Int sign <- 0
    Bool hasDigit <- false

    traverse (data.defaultOrder() -> Char c) {
      if (sign == 0) {
        if (c == '-') {
          sign <- -1
          continue
        } elif (c == '+') {
          sign <- 1
          continue
        } else {
          sign <- 1
        }
      }
      if (c >= '0' && c <= '7') {
        hasDigit <- true
        total <- 8*total+(c.asInt() - '0'.asInt())
        continue
      }
      return autoFail<Int>(c)
    }

    if (!hasDigit) {
      return ErrorOr:error("missing digits in Int value")
    }

    return ErrorOr:value(sign*total)
  }

  binInt (data) {
    Int total <- 0
    Int sign <- 0
    Bool hasDigit <- false

    traverse (data.defaultOrder() -> Char c) {
      if (sign == 0) {
        if (c == '-') {
          sign <- -1
          continue
        } elif (c == '+') {
          sign <- 1
          continue
        } else {
          sign <- 1
        }
      }
      if (c >= '0' && c <= '1') {
        hasDigit <- true
        total <- 2*total+(c.asInt() - '0'.asInt())
        continue
      }
      return autoFail<Int>(c)
    }

    if (!hasDigit) {
      return ErrorOr:error("missing digits in Int value")
    }

    return ErrorOr:value(sign*total)
  }

  @type autoFail<#x> (Char) -> (ErrorOr<all>)
  autoFail (c) {
    return ErrorOr:error(String.builder()
        .append("failed to parse ")
        .append(typename<#x>())
        .append(" at '")
        .append(c)
        .append("'")
        .build())
  }
}